Lime stabilized construction: a manual and practical guide

1 LIME STABILIZED CONSTRUCTION LIME STABILIZED CONSTRUCTION 2
Lime Stabilized Construction
A Manual and Practical Guide

LIME STABILIZED CONSTRUCTION 4i LIME STABILIZED CONSTRUCTION iiLIME STABILIZED CONSTRUCTION
RecurrentdisastersinPakistanhavehighlightedtheneedfor
dedicated and innovative measures to reduce the negative
impacts of such events on populations in high-risk areas.
support to the most vulnerable families whose houses
safeguards the environment and enhances readiness for
and promoting vernacular construction.
One such technique is the use of lime to stabilise soil for
of shelters. Building on its earlier work with Heritage
promote DRR-informed construction since 2011.
The achievements and learning from Strawbuild’s work
2013. Corresponding posters illustrating various steps
in the process have also been developed to serve as
information for partners and communities.
We hope these resources will continue to enhance the
to face future disasters and equipping them with the skills
Enrico Ponziani
Chief of Mission
IOM Pakistan
Foreward from IOM
10 Euston Place
Leamington Spa
Warwickshire
CV32 4LJ
Director of the
Building Limes Development Group
Director Strawbuild
Sedum Cottage
Owen Street
Pennar
Pembroke Dock
Juliet Breese of Deaft Design
Michael Howlett
Co-Director of Strawbuild
International Organisation for Migration
www.iom.int

iii ivLIME STABILIZED CONSTRUCTION LIME STABILIZED CONSTRUCTION
Stafford Holmes and Bee Rowan are consultants
specialising in the use of traditional building materials
and are visiting lecturers with various higher educational
and demonstrations.
Bee Rowan is Director of Strawbuild and has more
construction materials and of inspiring and teaching
One of the UK’s foremost training companies in
lead partner in various European training partnerships
developing European training programmes in strawbale
Architects specializing in the care and repair of historic
and building limes for conservation and sustainable
construction. Director of the Building Limes Development
where specialist knowledge of building materials and their
application is required.
“Stabilized Soil as an Appropriate Building Material”
lime stabilized soil plaster and wattle and daub repairs
Evaluation of Limestone and Building Limes in Scotland
for Historic Scotland 2003.
Stafford is also author with Michael Wingate of Building
Both Bee and Stafford want to continue to support and
develop this initial lime and lime stabilised soil work in
About the Authors
So the question to humanitarian agencies is how best can
we meet this request with the limited resources and funds
while maintaining a high standard of construction so that
roof screeds that remain stable in wet conditions and
and indicate the potential for lime stabilized soil houses
from Pakistani historical religious buildings and the use of
Karachi based Heritage Foundation have been invaluable
predominant vernacular of this region. Communities are
familiar with and skilled in building with these materials.
valuing the traditional building methods is so vital and
can have so much meaningful impact. Communities do
or concrete blocks held together with sand and cement.
bricks and cement and replacing these elements with
when we consider how crucial it is to reduce carbon
have been part of this programme and would like to thank
Stafford Holmes and their Field Team.
Foreward from DFID (UK Department for International Development)

v vi
for further detail.
Strawbuild are pursuing research on solar powered
need development and would produce no CO2
.
reduce CO2
Pakistani lime burners. An understanding of how to select
is important.It empowers people to make the right choice
cause failure and the need to rebuild.
understanding how to use lime to stabilize local soils offers
and where the alternatives are often far less appropriate
Building with Earth and Michael Wingate co-author
with Stafford Holmes of Building with Lime. Relevant
for rural communities in Pakistan.Thanks too are due to
Humanitarian Shelter Advisor to DFID for consistent
and in supporting both the continued development of this
wonderful illustrator who has helped bring lime alive again
motivators introducing lime to the villagers where the
embracing lime stabilized soil construction methods and
LIME STABILIZED CONSTRUCTION LIME STABILIZED CONSTRUCTION
Preface
This manual has been prepared as a guide for the
housing. Hundreds of thousands of houses have dissolved
programmes across Sindh in 2013 and 2014 have indicated
the great potential for the use of lime in stabilising local
and the villagers are making their own minds up after
seeing the results.
funded Flood Resilience Programmes of Sindh. There is
used in Pakistan as an essential material in such traditional
stabilized soil programme is therefore both innovative use
of building lime use in Pakistan.
The programme calls on this cultural tradition as well
stabilisation of local soils facilities this at the lowest
possible economic and environmental cost.
and local building traditions use local soils as the principal
this tradition and allows the same architectural vernacular
concrete and other inappropriate materials will often be
raising and lowering temperatures well outside the comfort
that soil construction methods allow much improved and
in large quantities and are often low cost waste products.
One of the economic returns of using lime stabilized soil
it is meant that the soil will not dissolve underwater and
return to mud.
tests outlined in this manual to produce well tested and
dramatic cost saving when lime stabilized soil construction
is set against conventional construction materials - as

GLOSSARY (10 pages) 146
APPENDICES (17 pages plus last acknowledgment page)) 156
RECAP - Hydraulic Set from Non-Hydraulic Lime
and Clay Rich Soil or Pozzolan
174/175
STAGE 1 FIELD TESTING
Materials
1.1 Lime
Quicklime
Dry Hydrate
Lime Putty
LIME
QUALITY
TESTS
1.2 Soil
Clay
Silt
CLAY
CONTENT
FIELD TESTS
1.3 Sand
PARTICLE SIZE
ANALYSIS
1.4 Pozzolan
1.5 Fibre
1.6 Other
Burnt Brick Dust
Rice Husk Ash
Industrial Fly Ash
STRENGTH AND
SIZE TESTS
Cow Dung
Oil
Water
POZZOLAN
REACTIVITY
TESTS
USE THE BEST OF STAGE 1 FIELD TESTED MATERIALS FOR STAGE 2
2.1 Materials Selection
2.2 Calculating Lime
Proportions
Linear shrinkage
test results
(millimetre
shrinkage)
2.3 Mix Proportions
for Stabilization
Appendix 1
2.4 Mix Design for
Stabilization
Trial Mix Samples
Blocks
Cubes
Discs
2.5 Materials Preparation
STAGE 2 TESTING
Trial Mixes
FIELD
2.6 Lime Type and
Where to Use
2.7 Curing
Shading & Damping
for 28 Days
Carbonation and
Chemical Set
2.8 Test the Trial Mixes
SOAK Test
Strength Test
Permeability Test
2.9 Recording Ratios
2.10 Test Mix Recording
3.1 Testing of Production Mixes
3.2 Foundations
3.3 Bricks & Blocks
3.4 Earth Mortar
3.5 Cob
3.6 Rammed Earth
3.7 Wattle & Daub (Loqat)
3.8 Sample Render and
Plaster Panels
3.9 Plaster
3.10 Render
3.11 Floor Screeds
3.12 Decoration and Lime Wash
3.13 Roof Finishes
STAGE 3 TESTING
Building Components
USE ONLY SUCCESSFUL RESULTS FROM STAGE 2 FIELD TESTING FOR STAGE 3
Flow chart of the Manual’s 3 Stage Testing Sequence.
See inside the back cover of the Manual for a simplified overview of the process
FIELD
INDEX
INTRODUCTION 7
1.0 STAGE 1 FIELD TESTING: Investigate, Test & Select Available Materials 24
1.1 Building Limes 26
1.2 Soils 60
1.3 Sand 71
1.4 Pozzolans 73
1.5 Fibres 75
1.6 Additional Materials 76
2.0 STAGE 2 : Prepare and Test Trial Mixes For StabilizationFIELD TESTING 78
2.1 Materials Selection 79
2.2 Calculating Clay Percentage of Soil for Stabilization (Linear Shrinkage) 80
2.3 Mix Proportions for Stabilization - (Use of Appendix 1) 81
2.4 Mix Design for Stabilization - (Making Trial Mix Samples for Testing) 83
2.5 Materials Preparation 85
2.6 Lime Type and Preferences 87
2.7 Curing the Trial Mix Samples 93
2.8 Field Test Trial Mixes - (Soak Test, Step Test, Permeability Test) 94
2.9 Recording Ratios 97
2.10 Test Mix Recording - The Test Record Sheet 98
3.0 STAGE 3 FIELD TESTING: Manufacture & Continued 99
3.1 Introduction 101
3.2 Foundations 101
3.3 Bricks and Blocks 111
3.4 Earth Mortar 118
3.5 Cob 120
3.6 Rammed Earth 121
3.7 Wattle & Daub (Loh Kath) 121
3.8 Sample Render and Plaster Trial Panels 122
3.9 Plaster (For Internal Finishes) 124
3.10 Render (For External Finishes) 127
3.11 Floor Screeds 135
3.12 Finishes: Lime Stabilized Decoration and Limewash 138
Testing of Building Components

Introduction
What is Lime? “Lime is Life”
The difference between non-hydraulic lime (Pure lime) and Hydraulic lime
1) Pure Lime - ‘Non Hydraulic Lime’ (will not set under water on its own).
The Lime Cycle
The lime cycle is a concept that explains one of the many environmental benefits of using
lime. See Section 1.1.2. When lime is used in buildings it eventually reverts to calcium
carbonate which is the chemical from which it was originally prepared, so most of the carbon
dioxide gas driven off in the lime-burning is eventually replaced by carbon dioxide taken
back from the atmosphere (carbonation). The full sweep of the cycle is the conversion from
calcium carbonate to calcium oxide (giving off carbon dioxide), the combination with water
to form calcium hydroxide, and finally the carbonation in which water is lost and carbon
dioxide regained to form calcium carbonate chemically again. (See Fig 13: The Lime Cycle)
It is a journey of transformation, of how calcium carbonate in the form of hard stone
(limestone) is turned into a mouldable form (powder or putty based) to be mixed with soil
or sand to make building elements, and then reverts chemically back into calcium carbonate
again as part of the building. It sounds like the magic of alchemy, but this is not a cycle of
turning one material into another, it’s a cycle of turning the limestone back into calcium
carbonate in a more useful form to bind and protect our buildings. This process of turning
such as hard stone or sea shell into durable, protective mortars and renders is part of the
magic of lime, and has been used as such for thousands of years. Lime is literally formed
from life.
The sea shell is a clue as to the origins of lime. Lime stone, one of most abundant stones on
the planet, is effectively sediment made up primarily of calcium rich skeletons and shells of
sea creatures. These sediments were laid down millennia ago in layers of what eventually,
through various geological processes became calcium rich stone. Limestone will often show
some of the fossilised shells of these ancient sea creatures in its make up. (Appendix 5).
Such calcium rich lime stone is known as pure lime, as the sediments are made up of
relatively pure calcium carbonate with very few impurities. Pure lime is also known as
non-hydraulic lime, which is a reference to its inability to set or harden under water. As
opposed to hydraulic lime, which sets under water.
It is therefore a hydraulic set that is needed for flood resilience in Southern Pakistan where
the building elements exposed to water will need to stay stable under water for what might
be many months, and sometimes many months in consecutive years.
Commonly burnt limestone in Southern Pakistan however, is non-hydraulic. It is produced
for many uses including for the sugar industry and is of very high quality. It is pure calcium
limestone, which produces a non-hydraulic lime.
In the absence of a natural hydraulic lime, this manual is therefore a guide on how to prepare
and test mixes with non-hydraulic lime and other appropriate materials to produce a
hydraulic set for a range of building elements. (See also Fig 115 for a simplified overview)
2) Active Clay and Hydraulic Set (will set under water)
In this context, hydraulic set refers to the action, due to a combination of non-hydraulic lime
and active clay, or non-hydraulic lime and pozzolan that enables the resulting material to
resist damp or wet conditions and remain set under water.
‘Active Clay’is a simple term used as reference to a range of clay minerals which when mixed
(usually after burning) with lime, assist in creating the hydraulic set required to remain
stable under water for flood prone regions. The primary minerals usually present in these
clays are alumina, silica and iron oxide which may be found in the clay rich Indus valley soils
of Pakistan.
A hydraulic set is needed for flood resilience
A fully hydraulic set does not dissolve under water
This Manual is a guide that includes how to make a hydraulic set by
stabilising either clay soils with non-hydraulic lime or
stabilising low clay soils, sandy soils or sand with non-hydraulic lime
plus a pozzolan
Active Clays (clay minerals) found in many clay soils,
assist in creating hydraulic set
Fig 1: Every building element can be
lime stabilized: foundations, plinths,
walls, mortars, protective‘toes’, renders,
plasters, floor screeds and roof finishes.

Hydraulic Set
Active
Minerals
1. 2. 3. 4.
3, 4 & 5
5.
Fig 2: Five ways to create a Hydraulic Set:
Methods 3, 4 and 5 are typical methods in the Indus Valley for creating hydraulic set with
non-hydraulic lime at present.
3) Natural Hydraulic Lime
(Not normally available in Southern Pakistan)
Natural hydraulic limes are made by burning limestones which already contain active clay,
with the calcium rich remains of sea creatures laid down at the same time, which eventually
form a less pure limestone than that of non-hydraulic lime because of the added impurities
of the ancient sediments. It is the active clays in these sediments that are essential for
creating a set under water required for flood resilience. The active clays in the limestone
combine with lime when they are burnt together, to produce a natural hydraulic lime.
Rock strata of natural hydraulic limestone will contain varying amounts of active clay which
determines the degree of hydraulicity. There are classifications for natural hydraulic limes
which cover a range of hydraulic set from weak to very strong. These are known as feebly,
moderately and eminently hydraulic limes. (The stronger, eminently hydraulic limes have
been used in mortar for water mills, embankments and lighthouse walls that are
permanently under water).
There appears to be no commercial production from limestone containing clay in Sindh at
present. However it is very likely to exist, and the search continues. Until a limestone is
found that can be burnt to produce a natural hydraulic lime then the hydraulic sets needed
for flood resistant building material will need to be created using non-hydraulic lime.
4) Artificial Hydraulic Lime
Another method of creating a hydraulic set is with artificial hydraulic lime, which can be
made by burning a mixture of non-hydraulic lime and clay. It appears likely that the
hydraulic lime mortar used in the Sukkur Barrage of Sindh (1926 -1930) was of artificial
hydraulic lime made in this manner - from a mixture of local Rhori lime (pure non- hydraulic
lime) and local clay, burnt in specially constructed lime kilns at the construction site.
Detailed records of this are available in the Lloyd Barrage Museum at the Sukkur Barrage.
5) Making a Hydraulic Set with
Non-hydraulic Limes, Soils and Pozzolans
In areas with no natural hydraulic lime, and without producing artificial hydraulic lime, there
are alternative methods of making flood resilient buildings with low cost materials by using
selected local soils.
Two ways of achieving a hydraulic set with soils are by mixing lime with an active clay-rich
soil or by the addition of lime and pozzolan.
A hydraulic set can be achieved with:
1) Non-hydraulic lime plus active clay in the form of clay rich soil (containing
active clay minerals)
2) Non-hydraulic lime plus low clay or sandy soil (or sand) or other aggregates,
plus pozzolans (some containing active minerals)
It is possible to make a hydraulic set with a non-hydraulic lime and clay soil, if the soil
contains a sufficient proportion of active clay.
Precaution: Some soils however, contain clays that are not active and some contain
minerals that prevent a permanent set or stabilisation with lime. If soil cannot be stabilized,
this can be determined at the field testing stage (Stage 2) following which the soil should
either be modified and re-tested or discarded, and an alternative, satisfactory soil used.
The first stage is to investigate and test appropriate local clay soils to enable the production
of mixes that will stay stable under water by adding the appropriate quantity of good
quality non-hydraulic lime.

1. Clay Rich Soil:
Current research suggests that in rural Pakistan, most clay rich soils of the Indus basin
appear to include sufficient active clays to react with lime to provide hydraulic sets.
2. Sand or Sandy Soil or Low Clay Content Soil:
Where there are low clay content soils, or sandy soils or sand and other aggregates,
pozzolan may be added as an alternative or in addition to the active clay. The most widely
accessible, low cost form of pozzolans in Southern Pakistan found and currently available to
date, appear to be finely sieved burnt brick dust and rice husk ash.
Important: All mixes for components intended to remain stable under water must be
subject to testing first, until more is known about the variation in local soil types. Conduct
all three stages of testing first, as described in this manual to establish best materials and
proportions, and whether full stabilisation can be achieved.
6) Pozzolans as an Alternative to Active Clays
Without the active minerals in a clay rich soil, a low clay soil, sandy soil, sand or other
aggregates will need the addition of a pozzolan for stabilisation when they are mixed with
a non-hydraulic lime.
A‘pozzolanic’ reaction is another way of creating a hydraulic set. (Called pozzolan because
of the name of the town in Italy named Pozzuoli where the Romans obtained the sand and
volcanic ash over 2000 years ago for use in creating hydraulic mortars. The ancient Romans
were highly skilled in water engineering, and many Roman baths and aqueducts using
hydraulic mortars and pozzolans remain standing today).
Pozzolans
A variety of substances can act as pozzolans including finely sieved burnt brick dust, rice
husk ash, pulverised fly ash and other industrial wastes. The exact way in which many of
these materials produce a chemical set is variable, and without detailed laboratory analysis,
is unpredictable and will need field testing.
To be at their most effective, pozzolans normally need to be crushed and used in fine
powder form.
Note: Always wear a dust mask when working with any fine dust material.
7) Hydraulic Set and this Manual
The hydraulic set of materials is therefore central to construction methods in flood prone
areas. This manual explains the nature and application of specific, appropriate, low cost and
locally available materials, as well as their testing. Field tests and methods of assessing soils
suitable for lime stabilization are examined. The preparation of building limes and their use
with either clay soil or pozzolans to produce a hydraulic set are described.
Details of field tests for a range of mixes of limes and clay soils or pozzolans are given,
together with the site preparation of lime stabilized soils and lime stabilized earth building
elements.
Field test methods only are described in this manual as an initial guide to the lime
stabilisation of soil and as a way forward for immediate assistance for recovery in areas
devastated by flood. Due to the various nature of soils however, some may not be suitable
and some will require modification. The field tests therefore need to be followed with
detailed laboratory tests to establish the precise chemistry and other characteristics of
suitable and unsuitable soils. Until this is done, unsuitable soils can only be identified by
long term field testing.
For the village user, there is an emphasis on the illustrations, most of which are available as
posters and other visual aides with explanatory text, as this is primarily an educational or
training guide. It is not a construction manual and is confined to describing methods by
which the research, development and field testing of low cost local materials may benefit
rural communities.
There are now many manufactured materials that are water resistant, but mostly due to
difficulties of transport and cost, they are not available or appropriate for many
communities. Methods of using locally available materials that may provide greater
durability against flooding than are currently employed are examined and offered here.
This Manual explains how to make a hydraulic set with non-hydraulic lime
and other locally available materials
8) Benefits of Lime
There can be many reasons for the choice of lime as the preferred binder and stabilizer, not
only because it is an excellent material for stabilizing clay soils. This has been well
demonstrated in southern Pakistan where a great many local clay soils have reacted with
small amounts of non-hydraulic lime to create a hydraulic set, sufficient to remain stable
under water for many months.
In the context of communities in rural areas of the world, abundant limestone resources
indicate that there is the opportunity for lime to be produced and used locally in many
other ways. Lime has other attributes and uses in addition to those for building
construction. One of the most important of these is its contribution to improving human
health and hygiene.
Lime can for example, be used to assist the purification of water. It can be used to improve
soil for agriculture. Due to its high alkalinity, it has mild disinfectant qualities. The materials
with which a building is constructed may well affect the health of its occupants to a greater
degree than is generally realised. Lime mortars, plasters and renders, including those used
in conjunction with earth construction, are more vapour permeable (able to breathe) than
denser materials, many of which have been rapidly developed over the last century and are
impermeable. This can be the cause of‘sick building syndrome’, in which the health of the
occupants is placed at risk.
The long term disadvantages of impermeability in building fabric, particularly solid wall
construction, are increasingly being recognised.

Softer more permeable materials provide a comfortable environment. Moisture is allowed
to evaporate and is not trapped, as may happen when impermeable materials are used.
Trapped moisture can be the cause of mould growth, infestation and a breeding ground for
fungal decay and insects. On the other hand, permeable materials allow the evaporation of
moisture which helps to protect other adjacent built-in materials, such as timber and
ferrous metals, from damp conditions and associated decay.
Building limes facilitate the use of other softer and vapour permeable building materials
due to their compatibility with them. These materials may well be both low cost and locally
available. Soft brick, cob, earth block, wattle & daub and straw bale are examples.
One of the ecological benefits of lime is its contribution to a sustainable environment.
Efficient small scale local lime production results in lime binders having significantly less
embodied energy than cement (the manufacture of which has a very high environmental
impact), shorter transport distances and the re-absorption of carbon dioxide (CO²) in its
setting process. As such, pure lime production (non-hydraulic lime, as commonly found in
southern Pakistan) can be almost carbon neutral. Developing fuel wood plantations in
conjunction with small scale lime production would further enhance the ecological
benefits as part of a holistic and sustainable approach to the use of lime in rural areas.
In addition, there are various other benefits to using lime in building construction. Due to
its fine particle size, it is a sticky material which enables it to bind firmly and gently to other
surfaces providing early adhesion. It has good workability. Over the longer term due to the
precipitation of free lime, it can be self-healing in the repair of fine cracks.
POSSIBLE CO² EMISSION SAVINGS IN THE USE OF LIME STABILIZED SOIL
CONSTRUCTION
Table Figures based on a Target Number of 50,000 new build Houses
Item Required
amount per
house (Kg)
Quantity
per house
CO² Kg)
emissions per
Kg / brick
CO²
(tonnes)
emissions
per house
Amount for 50,000
houses (CO² tonnes)
Fired Bricks per brick
figure (0.23 CO²e per
Kg)
- 5,500 0.55 3.03 151,250
Cement (Average CEM
1 Portland Cement 94%
clinker)
600 600 0.95 0.57 28,500
Lime replacement
(CO²e reduced by 70%)
50 0.234 0.0117 585
Approximate Difference and Savings in tonnes of CO2
= a possible 180,000 tonnes of CO saved per 50,000 houses
Source: Magnus Wolfe-Murray, Humanitarian Adviser in Shelter for DFID Pakistan, and University of Bath,
Embodied energy and carbon in Construction materials (2008) Available at:
https://www.circularecology.com/nuqdjaidjajklasah.html
Fig 3: Possible CO² savings in the use of lime stabilized soil for the construction of 50,000
new build houses compared to conventional and energy intensive fired brick and cement use
2
Comparative Costings undertaken in Southern Pakistan between lime stabilized soil
construction material and burnt brick and cement demonstrated across different
organisations an average of almost 70% savings. The combined benefits of the low cost of
lime, clay soil, and pozzolans, the ecological and health advantages of their use, the fact that
limestone is often locally available, and that building limes may be produced on a small
scale are important considerations. In this context, incorporating lime is one of the most
appropriate methods of stabilizing soils for building elements that require a binder for their
modification and improvement. This is of particular relevance in flood prone areas of the
world.
This manual therefore examines a range of methods of identifying, preparing, testing and
using lime and soil together, with a focus on soil stabilization.
Some Advantages of Lime Use :
9) The Manual - 3 Stage Field Testing (See Figure 1)
Due to the extreme variation of soil types, an initial field test programme of three stages is
recommended: These are :
1) First, test individual primary materials for suitability. Specifically building limes for reactiv-
ity, soils for particle size and clay content, pozzolans for reactivity and fibres for appropriate
size and strength.
2) Second, test well-prepared materials primarily for stability under water. Fully cured trial
mixes should be tested to select the most appropriate and effective mix samples for each
building component, particularly the optimum lime proportion, before use in the main
work.
3) The third stage is the testing of fully completed, proposed building components using the
main production run materials and successful trial mixes before full manufacture. This is
followed by their continued testing throughout the main work to check for consistency of
quality.
1. Healthy, hygenic, anticeptic qualities
2. Low embodied energy
3. Rural sustainable development
4. Protects other materials
5. Stabilizes Soil
6. Assists the evaporation of moisture
7. Small scale local production
8. Encouragement of skills development
9. Compatible with other natural materials
10. Improves indoor comfort conditions
11. Carbon Neutral
12. Supports self-sufficiency
13. Flood Mitigation
14. Disaster Risk Reduction
15. Good workability
16. Beautiful

4) A fourth stage, which involves testing for long term durability and chemical research is
therefore not covered in this manual. The laboratory testing of final mixes should be
completed before use in the main work if there is sufficient time. This is predominantly soil
particle size, chemical analysis and compressive strength testing of all materials and mixes.
The three stage field testing programme may seem a long process but once successful
materials and their mixes have been established, careful replication of the same mixes with
similar materials from a particular region may be repeated indefinitely. The field testing of
materials, particularly soils, should be followed immediately with detailed laboratory
testing to ensure that only suitable or suitably modified soils are used. (The composition of
some soils may be unsuitable and cause serious defects or decomposition. These must be
identified for modification, or avoided completely prior to commencement of the main
work).
A flood resilient mix for the stabilisation of a particular soil can be established
and can then be used indefinitely subject to laboratory testing
3 Stage Test Programme Outline
1) Stage 1: Investigate, Test and Select Individual Materials
2) Stage 2: Make and Test Trial Sample mixes for stabilisation with varying lime
proportions made from selected, successfully tested materials in Stage 1
3) Stage 3: Testing of the building components using production run materials before
full production, then throughout construction, followed by longer term testing.
Verify final mixes before use by laboratory testing
Stage 1: Investigate, Test and Select Individual Materials
Test individual materials for suitability:
Lime - test for reactivity
Soil - test for clay content and particle size
Pozzolans - test for particle size and reactivity
Fibres - test for size, strength and record of durability
Stage 2: Prepare, Test and Select Mixes
Using samples of the best quality materials selected after satisfactorily passing Stage
1 field tests, prepare and field test fully cured trial mix samples of varying lime
proportions as set out in Appendix 1, for appropriate qualities such as stability under
water and compressive and tensile strength, before such as stability under water
and compressive and tensile strength, before proceeding to stage 3 testing and use
in the main work.
- render - workability, stability under water and crack resistance
- plaster - as for render
- floor screed - as for foundations, plus impact and crack resistance
- roof screed - stability under water, crack and impact resistance, and flexibility
Make 3 trial samples, of 3 different trial mixes, per building component;
Cure all trial mix samples for 28 days;
Strength Test the trial mixes for compressive strength;
SOAKTEST the cured trial mixes for stability under water - for as long as possible, not
less than 30 days, and preferably longer, related to anticipated periods of flooding;
Permeability Test screeds for pit linings (and roof finish screeds if applicable).
Stage 3: Manufacture and Continued Field Testing of Building Components
The manufacture and continued testing of building elements using successful field
test mixes from Stages 1 & 2
Test and adjust the stabilized mix proportions of all final building elements made
with production run materials before use in the main work. This requires the
construction of :
- render and plaster panels to test for workability, bond, crack resistance and
finish;
- test floor screed panels to test for robustness of finish;
- roof screed test panels for crack free flexible finishes and impermeability;
- aggregate particle size;
- block consistency for foundation and wall mixes for compaction;
- lime wash consistency and quality.
Following the initial 3 stage field testing prior to construction, longer term field
testing at regular intervals during the course of construction should be carried out
to check for consistency.
The steps in each Stage are described in detail in the Manual.
Stage 4: Laboratory Testing
Laboratory Test Successful Mixes for Validation of Field Test Results
(Primarily for Wet and Dry Compressive Strength and Soil Analysis)
This Manual does not extend to laboratory testing, although it is hoped laboratory
tests can be undertaken on a selection of successful field tested samples from the
2013-2014 Flood Resilience Programmes in Northern Sindh, to correlate with field
test results.
Using the Guide to Initial Lime Proportions (Appendix 1), make trial mixes for all
building components to determine the optimum lime proportion for appropriate
qualities:
- foundations – compressive strength and stability under water
- wall blocks – as for foundations plus tensile strength
- mortar – as for foundations

Contents
FIELD TESTING: STAGE 1 - MATERIALS
STAGE 1 INVESTIGATE, TEST & SELECT AVAILABLE MATERIALS
1.1.1 Safety Precautions
i) Key Points
ii) Slaking
iii) Hot Mixes
1.1.2 Building Limes
i) Building Limes Introduction
ii) Production of non-hydraulic lime: : The Lime Cycle
iii) Storage and Protection of Quicklime
1.1.3 Quicklime Preparation
i) Crushing of Quicklime
ii) Safe handling of Quicklime
1.1.4 Field Testing Quality of Quicklime
i) Observation Tests (under burnt / over burnt)
ii) Six Second Test
iii) Gain in weight measurement
iv) Quicklime Reactivity Test
v) Lime Reactivity Test - The Slaking Time Measurement
vi) Lime Reactivity Test - Temperature Measurement
1.1.5 Dry Hydrate Preparation
1.1.6 Field Testing Quality of Dry Hydrate
i) Fineness
ii) Density
iii) Hydraulic Dry Hydrate
1.1.7 Field Testing Quality of Lime Putty
i) Lime Putty Density Test
ii) Lime Putty Consistency Test
iii) Lime Putty Soundness (for High Quality Finishes)
iv) Lime Putty Fineness (for High Quality Work)
1.1.8 Lime Putty Slaking & Settlement Pit Preparation
i) Site Selection & Preparation
ii) Build Two Adjoining Pits
a) Slaking Tank Construction
b) Settlement Pit Construction
iii) Methods of Lining Pit
iv) Plastering the Pit
v) Protection of Pits for Curing
1.1.9 Lime Putty Production
i) Slaking
ii) Safety
iii) Lime Putty Settlement
iv) Lime Putty Storage
v) Maturing the Lime Putty
1.1.10 General Site Preparation for Lime Stabilized Work
i) MixingYard
ii) Block Making Production
1.1 BUILDING LIMES
Materials
materials in Stage 1
Manufacture and Test Building Components

1.1.11 General Tools & Equipment for Lime Stabilized Work
1.2 SOILS
1.2.1 Soils Introduction
1.2.2 Ingredients of Subsoil
i) Gravel
ii) Sand
iii) Silt
iv) Clay
1.2.3 Suitability of Ingredients for Lime Stabilization
1.2.4 Obtaining Soil Samples
1.2.5 Clay Content - Simple Field Tests for Clay Content
i) Wash Test
ii) Shine Test
iii) Rubbing Test & Granularity
iv) Smell
v) Ball Drop Test
vi) Cigar Test
vii) Disc Test
viii) Sedimentation Test (Jar Test)
ix) Linear Shrinkage Box Test
1.3 SAND
i) Observation
ii) Sand Particle Size Analysis
1.4 POZZOLANS
i) “Reactive Minerals”
ii) Pozzolanic Reactivity
1.5 FIBRES
1.6 ADDITIONAL MATERIALS
1.6.1 Cow Dung
1.6.2 Oil
1.6.3 Water
Stage 1 – Investigate, Prepare & Test Materials
1.1 Building Limes
1.1.1 Safety Precautions
i) Key Points
Lime is an excellent building material. It provides clean and uniform finishes, and can help
protect buildings from water - both heavy rains and floods.
However, lime needs extreme care when mixing and handling before it carbonates and
hardens (cures and sets) on the building.
Lime is an alkali and can burn, particularly when in the form of quicklime. Quicklime in any
form, including dust, should not be allowed near or in the eyes nor onto wet or damp skin
or clothes, when it would become active and burn. To protect your skin, rub hands with
barrier cream or oil (such as coconut or linseed oil) before working with the lime, and wear
gloves and goggles or glasses.
Do not work alone when mixing lime, and make sure your skin and eyes are well protected.
Crushing quicklime can be dangerous. Wear protective clothing, eye protection, face mask,
gloves and shoes or boots (not open sandals) (Fig 4).
Fig 4: Protection of the Eyes
Do not splash quicklime into
eyes or onto skin
Contents STAGE 1 INVESTIGATE, TEST & SELECT AVAILABLE MATERIALS

ii) Slaking
Mixing the lumps of burnt limestone (known as‘quicklime’) with water to make lime putty
is especially hazardous.
Figs 5: Always add Quicklime to Water, not water to Quicklime
When making lime putty, always add the lime to the water (not water to lime) (Fig 5) and
ensure that the quicklime lumps are always fully submerged.
The reaction can release great heat, and the mixture can boil and spit when it is mixed with
the water. Large quicklime lumps can explode if only partially immersed in water. This
sometimes happens when there is not enough water in the slaking tank to fully submerge
the lumps of lime.
Avoid splashing.
If it spits into the eye, it can blind. (Fig 5)
If it splashes onto bare skin, it can burn. (Fig 7)
Fig 6: Lime Putty Production
When slaking, wear eye protection,
cover and protect bare skin. Wear long
sleeves. (Fig 6)
Wear waterproof gloves. Wear enclosed
footwear. (Fig 8)
Keep children and animals away from
the lime settlement pit. Surround the
pit with any form of fencing for safety,
or a barrier, like old wire and branches.
(Fig 9)
Fig 7: Protection of the eyes and skin:
Remove lime splashes immediately with clean water.
Put some drops of acidic lemon juice or vinegar into
hand-washing water to help neutralise the drying effect
of the alkaline lime.
Fig 8: Wear Protective Clothing when working with Lime

When working with lime always keep buckets of clean water close by, for eye and skin wash-
ing. (Figs 7 & and 10)
Fig 10: Always have Clean Water available
Fig 9: Protection of Lime Pit: Keep children and Animals safe
If the skin suffers a lime burn, it will need washing well. Vinegar or lemon in the water will
help neutralise the lime, as will dabbing the affected area directly with vinegar or lemon
juice. If the burn is bad, seek medical assistance. (Figs 7 & 11).
If wet lime splashes into the eye, immediately get help to flush the eye with clean water.
Keep flushing the eye for several minutes. If the eye remains bloodshot and sore, seek medi-
cal assistance. It is important to wear eye protection to prevent this from happening. Lime,
particularly quicklime in the eye can cause blindness. (Fig 7)
Fig 11: Health and Safety Equipment

iii) Hot Mixes
The term‘hot mix’is used to describe the result of the process of mixing quicklime directly
with aggregate, mostly soil or sand, where the soil or sand is either damp, or mixed dry with
the quicklime and the mix then dampened. (Fig 12). Depending on the use for the mix it
may be necessary to first crush the quicklime to powder. (See also Section 3.2.1).
If the soil is clay rich, and renders, plasters or block mixes are being stabilized, the use of
quicklime in very fine powder form is more reactive than lime putty or dry hydrate and is
recommended. This may have to be produced by crushing or grinding best quality selected
quicklime.
The hot mix process can be dangerous, as it creates heat and lime dust which can burn.
Cover your nose, bare skin and eyes when using quicklime powder and hot mixing. Check
the wind direction and ensure that quicklime dust does not affect anyone or anything
downwind of, or adjacent to the work.
Fig 12: Hot Mixing - Add crushed quicklime into a damp mix, ensure uniformity
of colour and that all quicklime has slaked. Keep damp, then use
immediately and continue to keep damp.
i) Testing Building Limes
This section advises on the first stage of investigation, which is to examine potentially
suitable building limes. Simple field tests are described to help determine whether the lime
is likely to be satisfactory in stabilized construction, and includes lime in the form of
quicklime, dry hydrate and lime putty. Dry hydrate and lime putty are produced from the
quick-lime, which needs to be of good quality - freshly burnt and highly reactive. The older
the quicklime is, and the more it has been exposed to the air, the poorer the quality and the
less reactive it will be.
When‘lime’is referred to in the Manual, it is referring to non-hydraulic burnt lime and is used
as either non-hydraulic quicklime, non-hydraulic lime putty or non-hydraulic dry hydrate.
(See sections 1.1.7 & 1.1.9)
1.1.2 Building Limes
First: Always test the Lime
Limes are tested for their reactivity
Well burnt, finely powdered, fresh quicklime is the most reactive
(Non-hydraulic) Dry hydrate(Non-hydraulic) Lime Putty(Non-hydraulic) Quicklime

Fig 13: LIME CYCLE
ii) Production of Non-hydraulic Lime: The Lime Cycle - See Figs 13 and 115
(Non-hydraulic quicklime, non-hydraulic lime putty and non-hydraulic dry hydrate)
The Lime Cycle referred to in the introduction, starts with the heating (burning) of the quarried
limestone (calcium carbonate - CaCO3
) in a kiln, at relatively low temperatures of between 900 and
1000 degrees Celcius, during which carbon dioxide (CO2
) is driven off to produce quicklime
(calcium oxide (CaO).
Quicklime: If well burnt, the quicklime will generally be white and light in weight, up to 44% lighter
than the original limestone (calcium carbonate) due to the loss of carbon dioxide. Fresh quicklime
is highly reactive and unstable and must be treated cautiously as it will react with moisture very
rapidly and can burn.
Lime Putty: The quicklime is hydrated (slaked) with a lot of water (excess water) by immersion in a
slaking tank where it is raked continuously to form a slurry and then settles out as lime putty.
Dry Hydrate: The quicklime is sprinkled with minimum water to form a dry hydrate powder.
Chemically, both forms of hydrated lime (lime putty and dry hydrate) are calcium hydroxide:
(calcium oxide CaO) + water (H20) forms calcium hydroxide Ca(OH)2.
Carbonation: The lime in either form is traditionally mixed with well graded (different sized) sharp
sand to form mortars, renders or plasters, which in correct curing conditions (keeping shaded and
regularly dampened for 28 days), will carbonate on the walls through the re-absorption of carbon
dioxide (CO2) into the mix and evaporation of the moisture forming calcium carbonate. Which is
where the process started :
(CO2 + CA(OH)2 - H20 = CaCO3).
Lime takes Time: But it doesn't end there - the lime as part of the building continues to increase in
strength and protective ability over time.
Carbon Neutral: And the process, through reabsorption of the carbon dioxide, released during the
initial heating, is an almost carbon neutral cycle so offers an environmentally sensitive and
sustainable construction material.
iii) Storage and Protection of Quicklime
Ensure if at all possible, that quicklime is sealed in double-lined, airtight and waterproof
bags. The quicklime needs to be kept dry and as fresh and airtight as possible. It will
degrade if exposed to the air (it will start to “air slake”, i.e. carbonate and lose its binding
properties). And it is dangerous to allow the quicklime to get wet - fire or an explosion
could result. Keep the weather proof bags of quicklime DRY, airtight and well sealed at all
times until used. Store them on raised ground. Protect from rain. Keep the bags tightly
closed. (Fig 14). Use quicklime fresh from the kiln, preferably within 3 days of burning. If the
age of the quicklime or quality are not known, carry out quicklime reactivity tests before
use, as detailed below. Compare the reactivity of this quicklime with fresh quicklime from a
local supplier at regular intervals to ensure consistent quality.
The curing regime is critical to both carbonation and chemical set for lime soil
stabilization. Keeping the work damp and shaded for 28 days is best practice.
See note on Carbonation in Section 2.7 ii)

Fig 14a 1) Loading Quicklime
14a 2) Burning Limestone in a lime kiln
14a 3) Bagging quicklime with gloved
hands into watertight and airtight bags
Quicklime
Limes are tested for their reactivity. Quicklime needs to be used fresh from the kiln, which
is when it is most reactive. If it is not possible to use it quickly, slake the quicklime with
excess water and store it indefinitely under water as lime putty, where the quality will
continue to improve. (See section 1.1.9 on lime slaking and lime putty storage).
1.1.3 Quicklime Preparation
Fig 14b: Protection of Quicklime :
Protect the Quicklime from Moisture
Use Quicklime fresh from the kiln or store in airtight bags & keep dry, or slake to lime
putty, where the quality will continue to improve.
Fig 15: Crushing Quicklime to Powder
Protect Quicklime from rain and damp.
Keep the bags well sealed from the air at all
times until used.
i) Testing the reactivity of quicklime
prior to the purchase and delivery
of the quicklime is essential to
ensure that it is of the best quality
and is sufficiently reactive. Mixes
that incorporate lime of a poor
quality are likely to fail.

Methods of field testing quicklime to establish its quality are set out in Section 1.1.4 below.
It is very important that the quicklime is well burnt, fresh from the kiln, and contains no
under-burnt or over-burnt material. Confirm this through testing, and then either on a
small scale with hand tools and a sieve, (Fig 15), or on a larger scale with a machine such as
a jaw crusher, or ball mill, or a roller mixer, crush the quicklime separately.
These machines are widely manufactured and many types are produced that can be hand
or animal powered. The ideal crushing machine to select is one that is able to crush both
quicklime to powder and pozzolans to the fine particle sizes recommended in Appendix 3.
(Fig 16).
The lime dust is dangerous and must not be breathed in. Wear a dust mask and eye
protection. Wear gloves and protective clothing.
Keep children and animals away from hot mixing, lime putty, and covered piles of coarse
stuff. (‘Coarse stuff’is a mixture of lime putty and aggregate, usually sand, which is stored for
short periods to mature for use as a plaster, render or mortar). (Fig 17).
The powdered quicklime to be used should be fully reactive and pass through a 0.850mm
mesh (No.20 sieve) for blocks or a 0.180mm (No.80) sieve for render. (See Appendix 4: Sieve
Sizes in the Selection or Grading of Materials).
Mixes made with poor quality lime are likely to fail
Fig 16: Hammer Mill - one of various
mechanical methods of crushing quick-
lime.
Always protect eyes, nose and mouth
when crushing quicklime. Do not inhale.
ii) Safe handling of Quicklime: The carriage of quicklime should be in wheelbarrows, or one
bag should be carried between two people. Do not carry bags of quicklime on the head.
Quicklime dust is dangerous and caustic and can burn, especially in the presence of
moisture such as sweat.
1.1.4 Field Testing Quality of Quicklime
It is important to use lime that is fully reactive. Quicklime that has been under-burned,
over-burned or exposed to the air for too long and has absorbed carbon dioxide will have
lost some, if not all of its binding properties. This section describes some field tests to
determine whether quicklime has been correctly burnt and is sufficiently reactive.
i) Observation Tests
Under-Burnt Limestone
This will be heavier than a fully burnt stone of the same size. It may contain a core of stone
which has not calcinated (where the heat has not penetrated fully). The core is recognizable
by its different colour, texture and density from the surrounding quicklime. Its core would
remain as residue in the water following slaking. (Fig 18).
It is important to avoid crushing up any under-burnt material for use in mixes as it is unlikely
to stabilize the soil and will have very little binding properties, if any.
To check whether two stones have been badly under burnt, knock the cores together. If they
have remained as stone they will make the sound and feel like two stones clacking together,
which is what they are. This can be done when the surrounding quicklime has been
removed.
Fig 17: Keep Children and Animals Safe from all lime work

Over-Burnt Limestone
The method of burning limestone, kiln design, fuel used and type of limestone will all affect
the quality of quicklime produced. Lime should be burnt at about 900 degrees Celcius
(900ºC) or a little above this. Over-burning is likely to be minimal when wood is used as the
fuel, but extremely high temperatures (up to 1400ºC or more) can be reached with coal,
coke and even charcoal. Burning temperatures of external uncovered small scale kilns will
be affected by weather conditions, particularly wind strength and direction. Generally, the
higher the temperature and the longer this has been maintained, the greater the quantity
of over burnt material and clinker produced. Pure lime can become dead burned and lose
its reactivity, and hard burnt particles may take weeks or months to slake. Over-burnt
material can usually be recognized by a darker hard crust or clinker on the surface, or
surrounding the burnt stone.
In addition to observing these signs, a further check is to test for reactivity to compare with
well burnt lime as described below. Field tests to ensure quicklime has been fully calcined
and is fresh, without having absorbed carbon dioxide or moisture are as follows:
ii) Six Second Test
Place small lumps of quicklime into an open mesh container such as a small sieve or kitchen
colander. Dip the container and contents into a bucket filled with fresh clean water so that
the quicklime is fully covered. Hold it in position below the water for six seconds only, lift out
the container, allow it to drain and empty the contents on to a dry inert surface such as a
metal tagheri, pottery, stone or metal bowl or bucket for observation. (Fig 19).
Immediately after emptying the contents, good quality lime will behave in one of the
following ways:
Fig 18 - Check the Quicklime is not
under burnt or over burnt. Do not use
underburnt quicklime.
To check if a piece of Quicklime is well
burnt, break the piece in half to check
that it is white all the way through.
Underburnt: the core will be a darker
colour. Do not use.
Overburnt: darker in colour and
possibly shiny
Pure Lime: (non-hydraulic lime)
The lime hisses, swells rapidly, breaks up, increases in temperature sufficiently to produce
water vapour, and turns to powder almost immediately or within a few minutes. This
process is termed slaking. Consistency of putty remains unchanged and will never set under
water. Volume is at least doubled by slaking.
Hydraulic Lime:
It is currently unlikely that in Southern Pakistan a burnt limestone will produce hydraulic
lime. If so however, the hydraulic lime in this test expands and breaks down to powder more
slowly than the pure lime. The most hydraulic limes take the longest to slake. Following
slaking it may be further tested for hydraulic properties by placing it under water to check
whether it will set on its own. If so, this confirms it is a hydraulic lime. The degree of
hydraulicity is related to the time it takes to set solid, generally between 3 and 20 days. (See
‘Building with Lime’Appendix 1 page 281).
Fig 19: 6 Second Test

Fig 20 - Check the Quicklime is
Burnt Properly
iii) Gain in Weight Measurement
The process of burning can reduce the weight of pure limestone by up to 44%. In
re-absorbing the carbon dioxide as well as moisture from the air, quicklime gains
weight and loses reactivity. (Fig 20)
A sample of the quicklime under test may therefore be carefully weighed for
comparison with a sample of fresh, well burnt quicklime of identical source and
volume. The initial control samples must be taken fresh from the kiln immediately
following a good burn. A good burn can be judged by the successful conversion of
all, or at least 95% of the stone in the batch (i.e no over burnt or under burnt
material).
To test the extent to which quicklime may have deteriorated over time, equal
volumes of it should be weighed.The difference shown by the increase in weight will
be that of the moisture and carbon dioxide absorbed, during the time between the
quicklime being removed from the kiln and received on site.
The amount of carbon dioxide alone may be checked by heating a sample at, say
80°C for half an hour (over a fire or in the sun), to drive off the moisture, and
re-weighing it. (As a guide, specifications for commercial lime in the UK state that the
carbon dioxide content should not exceed 5%).
iv) Quicklime Reactivity
This is a comparative test based on the amount of heat produced by the chemical reaction
of calcium oxide with water. It is more appropriate for the purer limes mostly used in
Pakistan at present. A fully calcined, freshly burnt pure limestone will rapidly rise the
temperature of water shortly after immersion. This reaction can be measured by timing
alone if the water boils, or by measuring the rate of temperature rise.
a) Lime Reactivity Test - The Slaking Time Measurement
Using a small 2 litre (or quart) metal container, half fill it with one litre of water maintained
at a set temperature, which could be room temperature, or about 25°C.
Fully immerse half a litre of a representative sample of quicklime. All quicklime lumps in the
sample need to be the same size, which could be about 25mm diameter, or preferably use
quicklime crushed to powder (and for accuracy, sieved through a 3.35mm mesh sieve).
Record the exact time taken for the water to be brought to the boil from the moment of
immersion.
Test quicklime produced at each firing or from different kilns. If the quality of quicklime in
each test is consistent, the time taken to raise the same volume of water from the same
temperature to boiling point should also be consistent.
If it takes longer or does not boil at all, this indicates the quicklime is less reactive, probably
containing calcium carbonate due to under-burning, or having been left exposed to the
air for too long. Alternatively, the quicklime may have been prepared from stone taken from
a different bed in the quarry that contains a lower proportion of calcium carbonate.
As a general guide, experience has shown that in ambient temperatures of 25 to 30°C,
reasonably reactive quicklime should boil water within between one and five minutes in
this test.
It is possible that temperatures of some pure (non-hydraulic) lime samples may reach close
to boiling, but not quite reach 100°C. If this is the case, do not use the lime for any building
purpose including lime wash. Discard, as it is not sufficiently reactive.
Alternatively, carry out a second quality check by using the Gain in Weight Measurement
field test as (iii) above on an identical sample from the same batch. (Temperature changes
for the slower slaking hydraulic limes can be slight and are more difficult to record. To make
measurement easier, the container should be well-insulated, or a vacuum flask could be
used).
In reabsorbing carbon dioxide as well as moisture from the air, quicklime gains weight,
and loses reactivity. Keep all fresh quicklime in air tight containers and if the fresh
quicklime cannot be used immediately, slake it to putty and store under water until it
can be used.

Fig 21: Lime Reactivity Test
1. Pour 1 litre of room temperature water into a 2 litre metal jug.
2. Add 500g of crushed quicklime to the water in the metal jug.
3. If the lime is good quality and lively, ready to use, it will boil the water within 5 minutes.
Stand well back. The mixture can bubble and spit when boiling, and will
burn eyes or skin. Wear safety glasses.
If the water does not boil, do not use the quicklime for any building purpose. It is not
sufficiently reactive. This method is more precise, but requires a thermometer and exact timing. (It can also be
useful for feebly hydraulic limes where the time to reach boiling point is longer, or may not
be reached at all, and for eminently hydraulic limes where the temperature rise may be very
small and much slower).
Prepare the same sample volumes, equipment and process as above but use a thermometer
to record the rate of temperature rise. It is important that the temperature of the water is
exactly the same at commencement of each test when the quicklime is immersed. Take the
temperature every 30 seconds for pure limes. (Fig 21).
The time and temperature taken at each reading can be recorded and compared to
previous readings, or related to experience with other limes.
1.1.5 Dry Hydrate Preparation:
Tested, fresh, reactive quicklime is sprinkled lightly with water from a brush or from a
watering can. Depending on both the amount of quicklime to slake to dry hydrate, and on
the the reactivity of the lime, the lumps of quicklime should fairly quickly start to‘bloom’as
they swell and crumble into powder. (Fig 22). Heat will be given off. Health and safety
precautions should be taken and children and animals kept away. Sieve the powder
through a 0.6mm mesh sieve (no. 30) and use the freshly prepared dry hydrate immediately.
Fig 22 - Dry Hydrate Preparation
In a metal container, sprinkle water
over one or two quicklime lumps.
If the quicklime is good quality, it will
quickly break down into powder.
The quicker it breaks down, the better
the quality.
Sieve the powder before use.
b) Lime Reactivity Test - Temperature Measurement

1.1.6 Field Testing Dry Hydrate Quality
i) Fineness
Sieve testing will give an initial indication of the quality of a dry hydrate. If production,
packaging and storage have been in accordance with the recommended National
Standards, the lime should pass simple particle size tests.
National Standards usually require the majority (99%) of all hydrate to pass a 180 micron
(No.80) sieve, (about 0.2mm). This fineness is advisable for fine plastering but is not
necessary for the majority of other applications for which building limes are required.
In terms of fineness only, the hydrate will normally be acceptable if it passes a 0.85mm (No.
20) aperture size sieve after continuously sifting 100g for five minutes, and leaves no
residue. The sieving process should be by shaking, without brushing, rubbing or punching
the lime through.
ii) Testing Dry Hydrate for Density
The density of dry hydrate may be determined in a field test by using a density vessel. A
simple field test for this is carried out in the same way as described for lime putty density at
1.1.5 (i) below. Some national Standards give a range of maximum density figures for each
class of building lime. The guideline value for maximum bulk density of pure dry
(non-hydraulic) hydrate lime is 0.5 g/ml (1 litre to weigh 0.5 kg).
iii) Dry Hydrate from Hydraulic Lime
As described earlier, Natural Hydraulic Limes (NHL) are made by burning limestones which
contain active clay.The active clays in the limestone combine with lime when they are burnt
together to produce a hydraulic lime which will set under water. Commercial Natural
Hydraulic Lime is usually sold in dry hydrate form as powder in air tight bags, traditionally
classified as feebly hydraulic, moderately hydraulic and eminently hydraulic.
Provided the hydraulic limestone has been well burnt and has a consistent mineralogy, the
dry hydrate bulk density can give an indication of its level of hydraulic content. The ASTM
bulk density levels for each lime classification are given in the table below :
Do not buy lime in powder form.
It is difficult to tell the difference between dry hydrate powder and air slaked lime, both
of which are sold in powder form in bags. It is therefore advisable to purchase lime in
quicklime lumps in airtight sealed bags, fresh from the kiln, in preference to lime in
powder form.
(If it is‘air slaked’quicklime powder, rather than dry hydrate, it will have lost some or all
of it’s reactivity and should be discarded).
Note: At present, there appears to be no availability of Natural Hydraulic Lime in Southern Pakistan.
1.1.7 Field Testing Quality of Lime Putty
To create a hydraulic set for flood resilient mixes it is essential that before use, all lime putty
is tested for quality. If the lime putty is not dense enough and is too thin, it will not stabilize
a soil or a sand and pozzolan mix.
For manufacture and production of lime putty, see 1.1.8 and 1.1.9
i) Lime Putty Density Test
An upper limit of 1.45g/ml is a standard set by several international standards for lime putty
of standard consistency. The putty density can be calculated with a standard size (½ litre or
1 litre) or graduated container of sufficiently regular shape to maintain precise and constant
volume each time the container is filled.
Fill the container with exactly one litre of the putty and ensure all air is expelled by tapping
it down until no further putty can be added. Carefully strike off surplus from the top.
Continue to tap down, strike off and add putty until there is no increase in mass.
The density is calculated by dividing the maximum mass of the putty in grams, by its
volume in millilitres, or for field test purposes, kilograms per litre.
Fig 23: ASTM Bulk Density Levels for Lime Dry Hydrate Classification
Dry hydrate of lime Bulk density (g/ml)
White(pure) lime. Non-hydraulic 0.5
Feebly (slightly) hydraulic 0.65
Moderately hydraulic 0.65 - 8.0
Eminently hydraulic 0.9 - 1.0
To create a hydraulic set, all lime putty must be tested first. If the lime putty is not
dense enough, it will not stabilize a mix for flood resilience

A simple field test method is to use any container that holds exactly one litre.This should be
carefully filled with the putty as described above and weighed. After deducting the weight
of the container, the putty weight in kilograms is the same figure as the density. The maxi-
mum weight of one litre of lime putty should be close to 1.45kg (Fig 24).
Only use putty of the density passing this test
1. Weigh a 1 litre plastic jug (so this weight can be subtracted from the end)
2. Fill the jug with 1 litre of thick yoghurt-like lime putty
3. Because good quality lime putty is much thicker than water, it will weigh more than water. The 1 litre jug of
putty should weigh 1.45Kg.
4. If it weighs less than 1.45Kg, leave the putty in the bottom of the lime putty settlement tank to become denser.
5. If it is much heavier than 1.45Kg, add a little water and mix well, weigh again to 1.45Kg and then use in mixes
All lime putty needs to be of the appropriate density.
If not, the density should be adjusted
Fig 24: Lime Putty Density Testing
If one litre of putty weighs 1.35kg it is starting to get too thin and its binding properties will
be reduced. Do not use. Allow the putty to settle for longer and drain off excess water from
the top to improve density. If on the other hand it is too dense, add a small amount of water
and mix it in well to re-test until the correct density is achieved. If the putty has been taken
from the settlement tank too soon or water on the top has not been drained off, it is likely
to be too wet. Allow the putty to settle out in the tank for a few more days and make sure all
covering water is drained off before removing it and testing for density again.
ii) Lime Putty Consistency Test
The simplest basic field test to check whether putty consistency is adequate for good
binding purposes, is to fill a container 3" in diameter by 2" high in a similar way to above. Use
a 30gm ½" diameter plunger to place on the surface of the putty. The putty consistency is
considered satisfactory if the plunger sinks to the depth of between ½" to 1" under its own
weight. A suitable plunger might be a whiteboard marker pen, emptied and then filled with
sand until it weighs 30g (Fig 25).
Remove water from on top of the lime
putty in the settlement tank before
taking lime putty for use. Only use the
thicker and denser lime putty from the
bottom of the settlement tank in mixes
1. Make a plunger weighing 30g, where its
end has a diameter of 1/2” (Fill an
ordinary marker pen with sand to 30g)
2. Make a small container 3” wide and 2”
high
3. Fill the small container with yoghurt-like
consistency lime putty
4. Gently place the plunger on the top of
the lime putty in the small container. Let
go.
5. If the plunger sinks under its own weight
by only 1/2”to 1”, it is thick enough.
Fig 25: Lime Putty Consistency Test

iii) Lime Putty Soundness
A test to ensure lime putty is sound, and establishes quality generally, is particularly
relevant where the quality of finish is important, such as mortar, render, internal plaster
work, limewash and decorative modelling.
Spread a thin layer of putty, about 2mm (1/12“) thick on a sheet of glass or clear plastic and
hold it in front of a strong light. If dark spots can be seen, these indicate the probability that
over burnt or un-reactive material is present and hence the possibility of a defect occurring,
particularly to finishes at a later date, due to delayed slaking.
iv) Lime Putty Fineness
Several National standards suggest that all putty for mortar and render base coats should
pass through an aperture size 2.36mm (No.8) sieve, and for finishing coats an aperture size
of 0.85mm (No.20) sieve leaving no residue (ASTM C5-79). If the putty is to be used for work
of a high standard such as internal plaster or decorative stucco, it should pass 0.18mm or
180 microns aperture (No.80 sieve). In order to achieve this finer material, the putty (or
slaked lime) should be washed through the sieve in a diluted form and then allowed to
settle out as a putty again. This can be done by selecting the appropriate sieve size when
slaking. (See Appendix 4).
1.1.8 Lime Putty Slaking Tank & Settlement Pit Construction
For the Production and Storage of Lime Putty (Figs 26 - 29)
Fig 26 - Lime Pit Preparation - For safety keep children and animals away from the
lime slaking and settlement pits
Making Lime Putty in the Village Environment
i) Choose and Prepare the Site: Choose a site where water is available, there is good transport
access, and where children and animals can be kept away.
Select a location where there can be elevated, shaded ground for storing bags of quicklime,
and space for a shallow lime slaking tank approximately 0.9m x 1.5m x 1.5m (3ft x 5ft x 5ft)
minimum, with space for at least one deeper lime putty settlement pit directly adjacent and
below it, approximately 0.9m x 1.5m x 1.5m (3ft x 5ft x 5ft).
It may be easier to construct the tank and the pit/s on a slope in the ground to help run the
putty down from the slaking tank to the putty storage pit/s. The size of the site for the lime
slaking and settlement pits will vary depending on the amount of putty required at any one
time.
ii) BuildTwo AdjoiningTanks or Pits: one for slaking the quicklime and one for settling out lime
putty.
a) Slaking Tank
Either dig a shallow quicklime slaking pit behind and higher than the putty settlement pit,
or build up a shallow slaking tank about 0.45m to 0.6m (1½ to 2ft) deep. Use blocks and
mortar of the same hydraulic mix as the settlement pit and plaster the sides and bases of
both with similar mixes as detailed below.
Fig 27: Lime Putty Production with
slaking and settlement tanks

Leave a brick sized gap for a weir and chute, or drainpipe, at the end of the slaking tank, as
the liquid slaked material (milk of lime) will need to run through a sieve placed underneath
the chute, into the settlement pit below. A slaking tank drain off pipe can be located below
the chute at floor level of the tank. This must be well sealed during the slaking process but
is useful for draining the tank before cleaning any defective (under burnt or over burnt
stone) material out when all slaking has been completed.
Sieves for Slaking Tanks: 5mm or 3mm aperture size or finer sieves can be used depending
on the use for the lime putty (Appendix 4).The sieves will keep lumps and unslaked material
out of the putty, which could damage the finished work.
b) Lime Putty Settlement Pit
Sizes of the pits for settling out lime putty will vary subject to the requirements of each area,
but initially allow for a pit 0.9m x 1.5m x 1.5m (3ft x 5ft x 5ft). The settlement pit will be
directly adjacent to, and below the slaking tank. A sloping ground surface and sealed shut-
tering or hatch at one end would assist access to the settlement pit for easy removal of the
putty.
Fig 28: Lime Putty Production with slaking and settlement tanks.
Overflow pipes should be added to both tanks for ease of drainage
and improved quality of putty
Fig 29: Slaking and Settlement Tank Dimensions: Minimum sizes are given for manual slaking
by 2 to 4 people. The putty settlement tank may be increased in size subject to the extent of new
construction required at any one time.

Fence off the site from children and animals to eliminate the risk of them falling into the pit.
(Fig 30). The settlement pit is where the lime putty can be kept stored under water,
maturing (and improving in quality) for weeks or months. This is a particularly effective
method of storing fresh lime if it cannot be used quickly after being burnt. Cover the pit to
keep protected from direct sunshine, to stop the water from evaporating too quickly, and to
keep the putty clean. (Figs 33 and 34).
iii) Suggested Alternative Methods of Lining Pits
The pit sides should be sealed, or lined which will help to hold water for longer, enable
regular use, and keep the putty clean.
a) Line the pit sides and base with burnt clay bricks bedded in hydraulic lime mortar, all well
laid with a smooth surface finish, (‘fair face’) in which case there may be no need to render.
b) Line the pit sides and base with lime stabilized unburnt blocks or bricks and hydraulic
mortar. There should be no need to render the walls provided they are well constructed
with a level finish - although a hydraulic render or floor screed mix will give additional
durability. (See section 3 for suggested block, mortar, render and floor screed trial mixes).
c) Finish the bottom of the pit with a screed mix of soil, powdered quicklime and finely sieved
pozzolan if the soil is clay rich, or a mix of lime, pozzolan and sand. (See also 3.11 on strong
hydraulic mixes for floor screeds).
d) Consider adding waste marble dust or other hard granular material where available, such as
crushed limestone grit to the mix for the floor, and possibly sides of the pit, to improve their
wearing qualities, or use polished stone or other hard material to make a smooth floor
finish.
Fig 30: Protection of Lime Pit from Animals & Children
iv) Plastering the Pits
Trowel on the finishing plaster in coats one to two centimetres thick, to well keyed and
wetted wall sides and possibly to the base of the excavation also.This will improve the water
holding ability of the pit and in keeping the putty clean. If the pit is intended for frequent
and constant use, a hard wearing and smooth floor finish to the base rather than a plaster
screed would be advisable. Notes on ways to prepare renders, plasters and floor screeds are
given in section 3. Cover the pit after rendering, damp down and cure as detailed below.
v) Protection for Curing
All lime stabilized mortar, plaster and floor screed lining the pit must be given time to cure
and harden before using the pit to slake lime. The mortars and plaster will need to be kept
damp and protected from hot sunshine or heavy rain, or they will not be strong enough.
The longer the lime work is kept damp, the more effective the hydraulic set. Keep the pit
covered with wetted sacks, cloths, plastic or a lid for about four weeks before using it for
slaking and putty production.
Fig 31: Lime Pit Preparation - Plastering the sides of the pit
The longer the lime work is tended and kept dampened, the more effective the
hydraulic set

1.1.9 Lime Putty Production
i) Slaking
Mixing or ‘hydrating’ the quicklime with excess water is called slaking. This active work
creates a lot of heat, (an exothermic reaction), so it may be better to slake at a cool time of
the day. (Fig 32)
Method: Half fill a shallow slaking pit with water. While one person carefully empties one
25kg bag of fresh quick lime into the water without splashing, another person keeps raking
the mix with a hoe. Make sure the quicklime lumps are always completely covered
with water as they are more likely to explode if they are not fully covered. The mix will get
very hot, and can boil and spit, so it is important to wear protective clothing. Keep adding
more water and no more than half a bag of quicklime at a time.
Keep moving the mixture around with the hoe to stop it forming sticky lumps at the bottom
and make sure that the quicklime is covered with water at all times. Depending on the size
of the slaking pit, a simple method is to have two people with hoes gently raking the mix
continuously. As the slaking tank is filled with more quicklime and water, the resulting
creamy milk of slaked lime will flow through the chute and run through the sieve or mesh
into the lime settlement pit below. Any large under burnt or over burnt lumps will stay in
the slaking tank. Smaller debris, and under burnt lumps will be retained on the sieve.
Make sure the quicklime lumps are always completely covered with water as they
are more likely to spit and explode if they are not fully covered
Fig 32: Use long handled Hoes to keep
the quicklime lumps moving and to
ensure all quickllime is fully submerged
under water at all times
Excess water on the top of the putty in the settlement pit can be recycled in buckets back
up to the slaking pit during the slaking process.
ii) Safety
Exercise extreme caution. Do not let the hot mixture spit into eyes or onto skin. Keep eyes
and skin covered. (See Section 1.1 on Safety Precautions).
Always have clean water ready for washing off lime when slaking. Keep a container of clean
water next to the work area for washing eyes or skin. Keep open bags of quicklime covered,
and keep them a safe distance away from the water and the slaking pit to avoid the risk of
water splashing on to them.
iii) Lime Putty Settlement
Over several days, the lime will continue to absorb more water and will settle to the bottom
of the settlement pit as lime putty. During this time the lime will expand and a thick putty
will result.
Only appropriately dense lime putty (like stiff yoghurt or cream) should be used for most
purposes and particularly stabilized mixes. Thin putty and insufficiently dense putty must
not be used as the mix may well fail under water. (See section 1.1.5 for appropriate Lime
Putty Testing).
iv) Lime Putty Storage
Keep the lime putty in the settlement pit covered with at least an inch (25mm) of water. If
the lime starts to dry out, it can harden, carbonate and become unusable. Top up the water
when needed.
Fig 33: Keep the Lime Putty under
an inch of water

Keep the top of the pit of lime putty covered, preferably with boards and a tarpaulin as well
as the water for both safety and to keep the putty clean. At least keep it shaded from direct
sunlight.
v) Maturing the Lime Putty
Leave the lime in the lime settlement pit under an inch of water for as long as possible for a
minimum of 2 weeks, preferably 4 weeks or more. The longer it matures under water, the
better it becomes.
1.1.10 Additional Site Preparation for Associated Lime Stabilized Work
i) Mixing Yard (shading is recommended)
Keep a clean flat, fenced area for all earth and lime mixing and related tools storage. Ideally
with a ‘hard standing’ or other hard mixing surface, so top soil from the site on which soil,
lime and other materials are being mixed, will not inadvertently be dug up and contaminate
the mix. Shade for workers is advisable. The mixing yard should be established in close
proximity to the lime putty settlement tank and to a ready water source, as close to the
construction site or block making site as possible.
ii) Block Making Production (prepare shade in advance)
Alongside the mixing yard, establish a block making yard next to a long, flat and shaded
area for the curing of the blocks once made. Prepare proper shade in advance if at all
possible. (See section 3.4 on block making).
Fig 34: Keep the lime putty clean by keeping the putty
settlement tank covered
1.1.11 General Tools & Equipment for Lime Stabilized Work
are given at Appendix 3
i) Basic Tools and Equipment for a village lime slaking and earth stabilization works.
See Figs 35a and b below, and see Appendix 3 for the names of tools and materials.
Fig 35a: Tools and Equipment (1)
See Appendix 3 for the names of the tools
(1)
(2) (3)
(4)
(5)
(6)
(7)
(8)

49 LIME STABILIZED CONSTRUCTION LIME STABILIZED CONSTRUCTION
ii) Mechanised Equipment, Types and Sources if Available
The research, development and availability of appropriate equipment, machinery and local
manufacturers is ongoing and the type of appropriate and most useful machinery is listed
at Appendix 3, including the Cinva Ram and agricultural back pack sprayers for misting
walls.
Fig 35b: Tools & Equipment (2)
See Appendix 3 for the names of the tools
(9)
(10)
(11)
(12)
(13)
(14)
(15)
(18)
(17)
(16)
1.2 SOILS
Soils are the next essential material to investigate and test in Stage 1 Materials Testing
1.2.1 Soils Introduction
Soils are formed mainly through the weathering action on rocks over millions of years. All
soils will vary according to the different rocks and minerals from which they have been
eroded. The main ingredients of soils are stone, gravel, sand, silt and clay. It is rare to find a
soil with all the ideal building properties. It is therefore important to check that there are
appropriate proportions of sand, gravel and clay in the soil to enable stabilization with lime.
This is with a view to providing a hydraulic set for a range of mixes that are to remain stable
in wet conditions.
1.2.2 Ingredients of Subsoil
i) Gravel: 20mm - 5 mm:
Small grains of rock. When mixed with lime and sand for the bulkier building elements, can
be used to form lime concrete. Gravel (known in Southern Pakistan as‘crush’) helps to give
compressive strength and reduces shrinkage of the building material Appropriate size
gravels can be selected for inclusion with larger items for such as well compacted trench
footings and foundations. Gravel can occur naturally but can also be produced artificially by
crushing rock. Crushed rock is widely available in Pakistan at present, used for road
construction and concrete aggregrate.
ii) Sand: 5mm – 0.06mm:
Grains of sharp, angular sand provide the skeleton of the building material, give it strength
and reduce shrinkage. (Many hill sands are sharp and angular, as are many high river sands.
Lower river sands, seashore sands and desert sands are often round sand, where the sharp
edges have been eroded by water or wind). A mix of large (coarse) and small (fine) grains of
sharp, angular sand helps to provide a strong bond in mixes. A sandy soil feels grainy and
will not stick together when wetted. Most Standards give 2mm as the changing point from
the finest gravel size to the largest sand particle size but for practical purposes and field
testing, sand grain sizes can be assumed to be up to 5mm.
iii) Silt: 0.06mm – 0.002mm:
Tiny particles most of which are too small to see with the naked eye. Silty soils feel silky, and
the particles are much smaller than sand. A silty soil will need the addition of clay or sand
or both for use as a building material. It is recommended that a soil’s silt content does not
exceed 20% for modified and stabilized earth mixes and 6% for lime : sand (and lime : sand
: pozzolan) mixes.
Gravelly, sandy and silty soils have no binding force. They will need the addition of either
clay or lime or both clay and lime to make a satisfactory building material. It is common
practice in some rural areas to use cow dung or a mixture of chopped straw and clay as
alternatives or together as binders. Although these are satisfactory in a continuously dry
climate, in very wet and particularly flood conditions, all the binding properties of these can
be lost with disastrous results.

iv) Clay: 0.002mm and below:
Miniscule particles, smaller than 0.002mm, which are too small to see with the naked eye.
These particles are chemically different to the other grains in the subsoil and can often swell
when wet, and shrink when dry. Clay is sticky. It has a binding force, and can bind the other
particles together into useable building material. The best soils to work with lime for
stabilization will contain significant proportions of both clay and sand.
1.2.3 Suitability of ingredients for lime stabilisation
Clayey soils can be stabilized through the addition of lime because of the way the clay
reacts with the lime.
For current traditional construction the most common and predictable aggregate used
with lime is well graded sharp sand. (A non-hydraulic lime and sand mix would require the
addition of a pozzolan to create a hydraulic set). The disadvantage of using a mix of lime
and sand only, is that far higher proportions of lime are required than for stabilizing clay rich
soil.
Mixtures of non-hydraulic lime and sand alone will not set under water. Most sands will not
assist a hydraulic set. Although non-hydraulic lime and sand mixes can produce excellent
mortars and plasters, they will not generally provide a hydraulic set.
Silty soils with very little or no clay or sand content will not work well as a building material
and should be avoided.
Understanding the clay content of the soil together with recognizing clay bearing strata is
important, so prior to designing a mix, the soil will need to be tested to establish its
composition, particularly clay content and whether it contains anything that will prevent
long term set and stabilisation.
Much less lime is needed to stabilize a clay soil, than is needed for a
lime : sand : pozzolan mix
1.2.4 Obtaining Soil Samples
Obtain a representative sample of soil by digging a trial hole. Remove all the top soil and
organic matter. Dig deeper to inspect the layers of soil. Go down beyond where the colour
of the soil changes, where there is no organic matter, and where the soil has no smell.
If there is extensive rock and large sized gravel, or the soil is unsuitable in any way, try
digging somewhere else. To save work, it may be best to dig these holes in conjunction with
other excavations required, such as for the lime slaking pit, drainage channels or
foundations. (Fig 36).
Trial holes for soil investigation are best dug with the exposed face to be inspected facing
south (in the northern hemisphere) to provide the best light on the new surface, and
different strata can be expected as the trial hole depth is increased. Test the soil from each
strata at different depths. Clay rich soils are best for stabilization. If there is a brickworks in
the vacinity, request a sample of their clay or soil before firing, or from the pit from whch it
is obtained.
If there is a pond or lake in the vicinity, this suggests the water-holding capabilities of a clay
soil. Equally, if puddles formed after rain remain longer in some areas, the soil is likely to
have a high clay content. If the soil when very dry, cracks and curls slightly, this also
indicates a clay soil.
The following simple field tests are to determine whether there is an adequate source of soil
with a clay content in a particular location. Carefully label each soil sample showing
location, depth and date.
Fig 36 - Earth Selection and Trial Holes
In areas of earth building, conduct research by asking the villagers, and particularly
the women, where the best quality clay soil for building is sourced. It may be that
there are two or more sources. It may be that the soils come from different depths.
Local knowledge is invaluable.

1.2.5 Clay Content - Simple Field Tests for clay content
Try to conduct several of the below tests. One test on its own will not necessarily establish
whether there is a clay content to the soil, or give an indication as to which soil, dug from
which depth, has a greater or lesser clay content.
Before conducting most clay content field tests, prepare the subsoil to a plastic state
(wetted, mixed and in damp form but not liquid form) and ideally leave for about half a day
to allow time for the clay to react with the water and other particles in the soil.
i) Wash Test
Rub a sample of damp subsoil between your fingers. If you can feel the grains of the soil
easily, this indicates a sandy soil. If it feels sticky, but it is easy to rub your hands (and
forearms) clean when it is dry, and where the residue is a fine powder, this indicates a silty
soil. If it feels sticky and fine, but water is needed to clean your hands when it is dry, then this
indicates clayey soil. (Fig 37).
Fig 37 - Wash Test
iii) Rubbing Test:
Rubbed between fingers, clay feels soapy and silt feels floury. Sandy soil will feel granular
and will break down quickly.
Granularity: With a little experience, an initial granularity test can be as simple as grinding a
little of the subsoil earth between the teeth and feeling for grain size.
iv) Smell:
Moist clay subsoil have no smell. If a moist sample of subsoil smells damp or loamy (earthy),
it is likely to indicate the presence of organic matter. Do not use in building. Try digging
deeper.
Fig 38 - Shine Test
ii) Shine Test:
Form a handful of damp subsoil into a ball and cut it with a clean, dry knife. If the cut surface
is shiny, the mixture has a clay content. If the cut surface is dull, it has a high silt content.
Additionally, a knife will will meet resistance when cutting into a clay soil - it will be
noticeably harder to cut through a ball of clay than a ball of silty or sandy soil. (Fig 38).

v) Ball Drop Test
Form a handful of subsoil into a ball about 50mm in diameter. The mixture to be tested has
to be as dry as possible, yet damp enough to hold a ball shape. When this ball is dropped
from about shoulder height onto a hard, flat surface, various results will give an
approximate indication of the soil content. (Fig 39).
a) If the ball shatters into many pieces it has a very low clay content, and its binding force is
very low. It cannot be used as a building material on its own, although its composition can
be adjusted following further tests.
b) & c) If the ball develops a big crack and possibly some smaller ones like those of the middle ball
in the illustration, and stays more or less intact, this may have poor binding force, but may
have enough clay and sand content to work well with lime in making renders and earth
blocks.
d) If the ball is flattened only slightly and shows no cracks it has a high clay content (high
binding force). This may need the addition of some sand to improve strength. The mix will
need a higher proportion of quicklime for effective stabilisation and may need fibres to
reduce cracking.
Fig 39 - Ball Drop Test
vi) Cigar Test - Clay Content
A field test to assess low, medium or high clay content. Eliminate particles larger than 5mm
by sieving the soil dry. Prepare a sample by adding just sufficient water to form a 6cm or
more diameter ball of plastic state, and roll it into a cigar shape of about 2 to 2.5cm
thickness and at least 20cm long. Slowly push the cigar roll off the edge of a flat surface and
measure the length of the roll at the point it breaks. If the broken length is less than 5cm, it
is sandy and/or silty soil. If the cigar is more than 15cm, it has high clay content. (Fig 40).
Fig 40 - Cigar Test

vii) Disc Test - Resistance and Shrinkage
A relatively fast field test for testing the resistance of the soil (clay content) when dry, and for
comparing the different shrinkage of soils. (Fig 41)
Take sub-soil samples from different depths or strata.
Remove any lumps larger than 5mm from the soil, and prepare the soil to a plastic
state.
Fig 41: Disc Test
Make small balls of 20mm to 25mm and form into discs inside small 10mm deep
plastic sleeves (cut from a half litre plastic water bottle for instance).
When fully dried, assess the resistance of the soil discs to crushing by testing
(applying pressure) between finger and thumb and assess and compare the
percentage of shrinkage of each disc.
If no shrinkage, and the disc crushes easily between finger and thumb/crushes to
powder, the soil will be sandy soil;
If there is a degree of shrinkage and the disc crushes easily between finger and
thumb/crushes to powder, the soil will be silty soil;
If there is high shrinkage and it is difficult to crush the disc / reduce to powder, this
indicates clayey soil.
viii) Sedimentation Test (Also known as the Jar Test)
A useful test giving a visual guide to the approximate proportions of different constituents
in the soil (Fig 42):
a) Fill a cup with relatively dry subsoil from one recognizable soil strata. Pick out any
large gravel and stones. Crush any lumps with a hammer or a piece of wood until the
soil is all crushed to the same size. (If possible, sieve the soil through a 5mm or smaller
aperture sieve).
b) Then place the cup of subsoil into a tall transparent jar, so the jar is about one third
full of the subsoil. The jar should have straight sides and a flat base to assist an
accurate reading of proportions.
c) Fill the jar three quarters full with water.
d) Add a teaspoon of salt (this will help the microscopic clay particles settle out of the
water quicker).
e) Shake the jar hard for 2 minutes, which will separate all the particles.
f) Allow for the material to settle out until the water is clear. This may take from a
couple of hours up to a day or two, sometimes longer, but note the settling out of the
initial layers particularly in the first 20 minutes. It is important that the jar is not
moved or disturbed at all while the contents settle, as this may make it difficult to
distinguish between the silt and clay layers.

Sand Layers: Almost immediately the larger sand particles will fall to the bottom, then the
finer sand particles. (Different sized sand grains make a better, stronger material and the
variation in sand particle size can be observed by eye).
Silt Layers: After about 20 minutes, the silt is likely to have settled on top of the sand layer,
looking like a separate darker or slightly different colour layer. Between 20 to 30 minutes
from starting to settle, carefully mark the top of this layer with a line, or with a rubber band
which will help distinguish the silt layer from the clay layer when the clay settles out later. It
can be difficult to tell the difference if the clay and silt are the same colour.
Clay Layer: After 8 - 12 hours (overnight), sometimes much longer, the majority of the very
small clay particles will have settled, giving an approximate guide to the ratio of the
different constituents.
ix) Linear Shrinkage Box Test
(See also Section 2.2: Establishing Lime Proportions for Stabilization)
Once a clay content to the soil has been established through the above simple tests, it is
possible to assess the approximate percentage of clay. This will be needed to help
determine lime proportions in the initial trial mixes for stabilization. A field test guide to the
clay percentage of a soil is through measuring in millimetres the shrinkage of soil when fully
dry, in an easily constructed‘linear shrinkage box’. The test will take about 7 days for the clay
soil sample in the box to dry thoroughly, so it is worth conducting the above soil tests and
the linear shrinkage test early.
Fig 42: Sedimentation (Jar) Test Sequence
a)
b), c) & d)
e)
f)
g)
Method: Make a wooden box with internal dimensions of 600 x 40 x 40mm. The box should
have a bottom but no top. (Fig 43). Oil the inside surfaces, which should also be smooth.
Take a sample of soil intended for stabilization and moisten it to its optimum water content
(check this with the ball drop test described in 3.2.4, Fig 79). Tamp the soil firmly into the
box with a stick and then smooth off the surface. Dry the contents for 5 - 7 days in hot sun,
or longer in dry shade or in a warm room.
The measurement in mm of the shrinkage along the length of the box when fully dry, gives
an indication of the percentage clay content of the soil. See Below Table Fig 44.
Section 2.3.1 on Stabilization
shows how this information is
used to determine trial mix
proportions of lime for
stabilisation of that particular
soil.
Fig 43a: Linear Shrinkage Box Test Fig 43b: Measure the millimetre
shrinkage when fully dried
Possible Shrinkage of ‘as dug soil’, in
600mm Mould Before Lime Addition.
Shrinkage
in mm
Percentage Shrinkage
Less than
12mm
1-2% 12-15%
12-24mm 2-4% 15-20%
24-36mm 4-6% 20-25%
36-48mm 6-8% 25-30+%
Possible Clay Content
of Soil Percentage
Fig 44: Chart of possible clay
content based on linear
shrinkage measurement when
dry

1.3 Sand
Field assessment of sand can be carried out mainly without tools although a few
accurately graded sieves are valuable for both field tests and grading materials for the main
work.
i) Observation
If clean sand is rubbed between moist hands it should leave no stain.The size and sharpness
of grains can initially be judged by eye and feel. The ideal sand has an optimum mixture of
coarse through to fine grains (Fig 45). In some cases, for wide joints or for lime concrete, a
proportion of grit or gravel is required with a grain size in the order of 3mm to 6mm or more.
Generally the fineness of the sand selected should relate directly to the fineness / thickness
of the work and finish required.
Nearly all sands will be composed of a mixture of different size grains but generally, for the
purpose of judging sand by eye, coarse sand may be assumed to be between 5mm and
2mm (3/16" to 3/32") and medium sand between 2mm and 0.65mm (3/32" to 1/32"). There
may also be very fine sand or dust from 0.65mm down to 0.06mm (60 microns). Material
with a particle size even smaller than this falls into the category of silt or clay, the proportion
of which can be determined by the sedimentation test described previously in Section 1.2.5
(vi).
ii) Sand Particle Size Analysis
This can be a simple test but it does require accurate sieves to carry out a detailed check that
the sand has the recommended grain size distribution for the best quality work. A series of
up to eight sieves would be required for a sufficiently accurate analysis. For the most
thorough work, laboratories carrying out particle size analysis will be equipped with a series
of sieves often in greater numbers than for manual testing, stacked and operated
mechanically.
Fig 45 - Particle Size Grading
Field Testing: For field test equipment the number of sieves can be reduced to possibly
three or four, each of an overall diameter about 250mm (10"). Weight can be reduced
further by using interchangeable sieve mesh bases for a single frame. The amount of sand
passing through a sieve mesh aperture size of 5mm (No.4) and retained on and passing
through meshes of 2mm (No.10), and 0.6mm (No.30) apertures will give an initial indication
of the overall particle size distribution, ie. the relative quantities of coarse, medium and fine
sand in the sample. (Fig 46)
Fig 46 - Particle Size Analysis Test

1.4 Pozzolans - Field Testing and Selection of appropriate Pozzolans
i) Reactive Minerals:
For stabilisation of low clay soils, sandy soils or sand with non-hydraulic lime, a reactive
pozzolan must be added. Those most easily available in Southern Pakistan are burnt brick
dust from crushed broken burnt brick or rice husk ash - both available from the brick kilns.
Natural and artificial pozzolans occur widely and many are predominantly rich in silica and
alumina. Natural pozzolans can be the result of volcanic action, and many artificial
pozzolans can be produced by grinding and/or sieving burnt waste products to very fine
dust. such as fly ash or broken clay tiles, bricks or pottery, but caution must be exercised to
ensure these are not over or under-burnt.
One of the most common and readily available pozzolans might be obtained from well fired
but low temperature (700-800°C) soft clay bricks made with a suitable clay. It is important
that the brick dust and broken brick is from a well fired brick, and not one that is
under-burnt or over-burnt. To prepare a typical pozzolan, waste brick dust could be
collected from a brickworks and sieved, or damaged bricks or clayware pots could be
crushed to powder. Waste fuel ash from various industrial and agriculture burning
processes is worthy of investigation as a potential source of pozzolan. Rice husk ash may be
one of these. The ash from a brick kiln using the clamp firing method, and using rice husks
as fuel was included in lime stabilized soil blocks in 2014. The blocks remained stable under
water and gave a wet confined compressive strength of over 4 N/mm² (600 psi) determined
by hand held concrete penetrometer.
The main test is the pozzolan reactivity test, outlined below. Or another simpler method is
by way of a submersion test on a cured, non-hydraulic lime and pozzolan sample mix. This
is to confirm the insolubility and compressive strength of the mix. Due to the curing time
required, this takes longer than the test with milk of lime illustrated in the reactivity test, but
can give a more conclusive result.
Fig 47a - Pozzolanic Reactivity Test
ii) Pozzolanic Reactivity
In this test the pozzolan reacts with milk of lime (lime putty thinned to the consistency of
milk), which is poured into a tall narrow glass or jar until it is one third full. This is followed
by an equal measure of the pozzolan sample which has been finely ground. (Sieve size 60).
The finer the pozzolan has been ground, the more reactive it is likely to be (fig 47b). For a
comparative test it is important that the milk of lime is the same consistency for all
pozzolans. One way to achieve this is to test each pozzolan at the same time using a series
of similar containers and the same milk of lime mix. Alternatively, if this cannot be done,
ensure that the lime has the same reactivity and the milk of lime has the same specific
gravity for all comparative tests.
Shake the container for two minutes every 12 hours for a week (ie in the morning and last
thing in the evening). Measure the depth and observe the bulk of the sediment shortly after
shaking. Compare this with a fresh mixture of the same material or with another pozzolan
given the same treatment. After 7 days the increase in the volume of the solid matter will
indicate the extent of pozzolanic reactivity. This can be measured by its increased height up
the jar. (Fig 47a)
Testing the comparative compressive strength of lime and pozzolan mix samples cured
over 28 days is a more accurate method but takes longer and requires laboratory
equipment. Laboratory tests involving crushing 50mm cubes to determine the compressive
strength of lime and pozzolan mixes can be found in Indian Standards IS 1727, 1344 and
4098.
Fig 47b: The finer the pozzolan is ground, the more reactive it will be

1.5 Fibres
Fibres added to mixes benefit the majority of building components as they add tensile
strength to the finished product. Typical of these fibres are chopped straw although harder
wearing fibres more appropriate for flood conditions could be sisal, jute, hemp or hair. Jute
and hair have a long history of effective use in lime renders and plasters, and straw in earth
plasters and daubs, although short chopped straw in lime plaster has been found in Fort Kot
Diji, Southern Pakistan, constructed over 200 years ago. Some dried reed or grasses
chopped or put through a chaff cutter may be an alternative, subject to testing. Cut the
fibrous material to about 25mm to 50mm (1”to 2”) in length, with a knife or a chaff-cutting
machine. (Fig 48). The chopped fibres help prevent plaster and other elements cracking
when they dry. Subject to testing, add about 10% or more chopped fibres to a wall block
mix, and 30% or more to a render or plaster mix by volume. (See Section 3.8 on making trial
render and plaster panels in which mixes with different proportions of fibre are tested).
Fibres should be evenly spread throughout the mix and not clumped together in places,
which would create a weakness. They should be spread evenly and continuously whilst the
mix is being turned over. The length and size of fibres needs to relate to the size of the
building element for which it is being used. There is a long tradition of incorporating fine
animal hair in lime mixes for best quality internal lime plaster, such as from ox, cow, goat and
deer.
Fig 48: Producing short, chopped Fibres
1.6 Additional Materials:
1.6.1 Cow Dung
For soil modification, the current use of cow dung is widespread and in regular use in many
rural areas of the world. It is used in conjunction with chopped fibres or on its own to
reduce shrinkage and improve the initial tensile strength and adhesion of earth bricks and
blocks, cob walling and render. The tendency of soils to shrink and crack when they dry,
sometimes with a corresponding detachment (falling off) of render from the wall, can be
reduced by the addition of these materials. Cow dung was and is frequently used with earth
or lime and sand for lining fireplace flues and areas close to and subject to heat.
The excellent binding and adhesive properties of lime and cow dung were used widely in
England up to the latter half of the twentieth century, and continues in use for conservation.
Cow dung introduced into the mix acts as a binder and improves plasticity. When used in
conjunction with lime and soil, there is an additional stabilizing effect and a noticeable
improvement to weather resistance. The significant constituent of the dung is a mucus
which reacts with lime to form a gel. The gel both stabilizes the clay mineral wafers and
supports the lime and sand until the lime carbonation and stabilisation process has been
completed, and final strength obtained.
Cow dung is therefore included in some of the proposed trial mixes for testing in areas
where this is an accepted and appropriate building material. Its addition may be especially
useful in external renders and roof finishes, assisting with additional wet-weather
resistance, and in minimising cracks - an important design consideration for roof finish
screeds over a large surface area on a less than solid substrate (although this is not a
recommended method of roof construction, but a widely used vernacular tradition in the
Indus Valley).
1 Ref. Building with Lime page 163
2 Ref.Ashurst & Ashurst

1.6.2 Oil
Water-shedding: Oils, particularly raw linseed oil, have traditionally been used as an
additive to lime wash in exposed areas to improve external water shedding. If used, these
should be added as a very small percentage of the final coat of lime wash, in the region of
5%. The more oil, the less effectively the lime wash is able to adhere, or allow the
evaporation of moisture from the wall.
Similar proportions of tallow (melted animal fat) or casein (milk protein) have been used for
the same purpose, and to reduce ‘dusting’ of the surface, but both of these animal based
products are prone to mould growth if applied in areas of persistent high humidity or
condensation.
Thinking ahead: Be aware that oil based additives in the last coat of the original lime wash
reduce the porosity of the wall, thereby reducing the bond for further applications of
limewash. Before any subsequent, future applications of lime wash therefore, the wall
would need preparation by stiff brushing down and the provision of a good key.
1.6.3 Water
One of the properties of lime is its ability to purify water. Less than chemically pure water
is therefore useable in the slaking of lime and for making lime stabilized mixes. However, the
purer the water used, the more consistent and of reliable quality the mixes will be. Subject
all trial mixes to Stage 2 field testing. If in doubt, have the water chemically analysed in a
laboratory, as various chemicals from either agricultural run-off, or from industrial waste
leaching into water supplies, may prohibit set or stabilization.
Saline water should not be used to slake lime or to make stabilized lime mixes. Although
preferably avoided, saline water in the absence of clean water may however, be used to cure
finished lime stabilized building elements, i.e. for damping down.
A relevant and timely report by Shawn Kholucy concerning a mix recently (2013) used at
Thorpe Hall in Suffolk, UK, confirms that the most satisfactory of four trial chimney parging
mixes was:
1 slurried cow dung:
1 lime putty:
3 haired aggregate
Other mixes suitable for testing include higher proportions of cow dung and lime putty with
less aggregate. They will need to include clay rich soil, pozzolan or hydraulic lime if they are
to be tested for flood conditions or to remain stable under water.
The report concludes with an explanation of the chemical reaction obtained by the use of
cow dung and lime in the mix. This results in the production of insoluble calcium carbonate
and soluble potassium hydroxide. The chemical reaction suggested by Dr. James Yates is
expressed as Ca(OH)2
+ K2
CO3
= CaCO3
+ 2K(OH). Although such a mix does not produce a
hydraulic set (on its own), the chemical behaviour of the cow dung in reaction with the lime
and the resulting insoluble calcium carbonate and soluble potassium hydroxide
demonstrates the potential improvement to performance and weather resistance by adding
cow dung to lime mixes.
Contents STAGE 2 PREPARE, TEST AND SELECT TRIAL MIXES FOR STABILIZATION
2.1.1 Soil Composition
2.1.2 Particle Size
2.2 Calculating the Clay Content of a Soil To Est ablish Lime Proportions for Stabilization
i) Linear Shrinkage Box Test
ii) Millimeter Shrinkage
2.3 Mix Proportions for Stabilization
2.3.1 Establishing proportions of Quicklime for Stabilization - Table Appendix1
2.3.2 Tables - Appendix 1
i) Quicklime to Soil Proportions
ii) Lime Putty or Dry Hydrate to Soil Proportions
2.3.4 Alternative Trial Mix Suggestions
2.4 Mix Design for Stabilization
2.4.1 Trial Mixes - in the form of blocks, cubes, discs for Different Building Elements
2.5 Materials Preparation
2.5.1 Soil Preparation
i) Soil Selection
ii) Soil Grading
iii) Soil Tempering
2.5.2 Lime Preparation - Quicklime, Dry Hydrate, Lime Putty
2.6 Lime Type and Preferences in Stabilized Mixes
2.6.1 Stabilization of Clay Soil with Quicklime
2.6.2 Stabilization of Clay Soil with Lime Putty
2.6.3 Stablization of Clay Soil with Dry Hydrate
2.6.4 Stabilization with Lime and Pozzolan
2.6.5 Unstabilized Mixes
2.7 Curing the Trial Mix Samples
i) Shading and Damping for 28 Days
ii) Carbonation and Chemical Set
2.8 Field Test Trial Mixes
2.8.1 Soak Test (Immersion Test) - The Field Test for Stability Under Water
2.8.2 Step Test - Field Test for Compressive Strength
2.8.3 Comparative Wet Compressive Strength Tests & Requirements
2.8.4 Permeability Testing
2.9 Recording Ratios
2.10 Test Mix Recording - Test Record Sheet
FIELD TESTING: STAGE 2 - SAMPLE MIXES

Stage 2 - Prepare, Test and Select Trial Mixes for Stabilization
Stage 2 is the making and testing of trial mix samples for soil stabilisation.
Having investigated, tested and selected individual appropriate materials in Stage 1 for
both suitability and reactivity, select and use the best and most reactive of these materials
to make trial sample mixes with with appropriate proportions of lime for testing under
water and for compressive strength.
2.1.1 Soil Composition
To make satisfactory plasters and building elements with soil, the soil should ideally have
appropriate proportions of both sand and clay, which will have been established in Stage 1
investigations and tests. Sand gives structural strength and clay bonds the ingredients of
the soil together. In order to obtain stabilization, the proportion of active clay to lime is
critical. Many soils and clays can be stabilized, but with some soils this is not possible.
Selection and/or modification of some local soils will be necessary. Where laboratory
testing is not practical, field testing of soils, as outlined in 1.2.5 and 1.2.6 is essential to
establish whether a soil and/or clay is suitable. Refer to Appendix 7 for relevant National
Standards that detail laboratory tests.
The addition of the correct amount of lime to the right type of soil can improve its strength,
and to varying degrees improve its resistance to erosion and stability under water.
Recognizable types of soil are:-
Lime binds the grains of sand together.
Lime reacts with the clay to stabilize the soil.
Generally soils with a high silt content are not suitable for building
construction and should be avoided, or be substantially modified by the addition of
other soils and/or suitable material.
Clay Content: Ideally for stabilization, the soil should have a minimum of about 15% clay
content because of the importance of the way lime interacts with the clay minerals, which
creates the hydraulic set. (Refer to Appendix 7 – Suitability of Soils for the Additions of
Lime).
Recap - Stage 1 checks :
- lime quality is fresh from the kiln and without loss of reactivity;
- soil composition - soil type, particle size and clay content;
- sand is sharp with a well graded particle size;
- pozzolanic material is reactive with lime;
- fibre strength and size (strong, dry and cut short)
- availability of other suitable materials : cow dung; oil
2.1.2 Particle Size
The principal qualities of soils, limes and pozzolans are to a large extent related to their
particle size. The precise definition varies from one country to another but for practical
purposes and field testing described in this manual they are as set out below:
Having established the soil composition, the percentage clay content needs to be
calculated, as described below.
2.2 Calculating the Clay Content of a Soil To Establish Lime Proportions for Stabilisation
i) Linear Shrinkage Box Test
The first stage required for lime stabilisation is to establish as closely as possible the
proportions of clay in the soil. This can be done by field testing methods set out below and
in 1.2.5 ix). (Figs 43)
These tests should be verified by laboratory testing.
The linear shrinkage field test gives an indication of the clay content percentage of a soil
through the measurement of the shrinkage of the damp sample when fully dried.
The extent of shrinkage indicates the approximate clay content of the soil.
The Appendix 1 Chart gives a suggested amount of quicklime to add for stabilization
trials according to the percentage clay content of the soil.
Fig 49: Chart of Comparative Particle Sizes
Particle Sizes
Gravel 75mm to 5mm
Sand 5mm to 0.6mm
Silt 0.06mm to 0.002mm
Clay 0.002 and finer
Powdered Quicklime Below 3.35mm (ASTM).
For foundations, field test say 5mm to dust, well
burnt, none over burnt or under burnt.
Lime Dry Hydrate Below 0.6mm
Lime Putty
(and Quicklime Powder for renders
and plasters)
0.180mm
Pozzolan 0.063m

The approximate clay percentage of the soil can be determined by conducting the linear
shrinkage test as outlined in 1.2.5 ix) and the results checked against the chart in Appendix
1 (Fig 50 below) to establish proportions of lime for making initial trial mixes.
ii) Millimetre Shrinkage Measurement:
When the sample is completely dry, measure how much it has shrunk away from one end.
Slide all the soil carefully, including separated pieces, tightly up to one end of the box.
Measure the gap created by the shrinkage in the soil and calculate the clay percentage as
shown in the table below (fig 50, Appendix 1). The extent of shrinkage indicates the
approximate clay content of the soil. The Appendix 1 Chart gives a suggested amount of
quicklime to add for stabilization trials according to the percentage clay content of the soil.
For suggested amounts of lime putty or dry hydrate, See Fig 52 below. Both are initially in
the region of double the amount of quicklime by volume required for stabilisation.
2.3 Mix Proportions for Stabilization:
2.3.1 Establishing Proportions of Quicklime for Stabilization - Appendix 1
The proportions of quicklime required for stabilisation will vary dependent upon soil type
but the Appendix 1 chart below, is a guide for evaluating initial trial mixes. All percentages
given are to the total amount of soil in the mix.
2.3.2 Simplified tables of Appendix 1
Simplified tables of Appendix 1 may be useful in that they refer directly to suggested
proportions of lime to soil (and as such, they may be easier to read) for use in the field and
village environment. See Fig 51 for Suggested Quicklime to Soil proportions;
Fig 52 for Suggested Lime Putty or Dry Hydrate to Soil proportions.
Possible
Clay
Content of
Soil
Percentage
Trial
Quicklime
Addition
Percentage
Proportion
of Lime to
Soil
(Lime:Soil)
Proposed Test Mix Proportions
Lime:Soil
(3 test speciments cubes per mix
minimum)
Shrinkage
in mm
Percentage
Shrinkage
Less than
12mm
1-2% 12-15% 3-6% 1:33-1:17 1:30 1:20 1:15
12-24mm 2-4% 15-20% 6-8% 1:17-1:12 1:15 1:14 1:12
24-36mm 4-6% 20-25% 8-10% 1:12-1:10 1:12 1:11 1:10
36-48mm 6-8% 25-30+% 10-12% 1.10-1.8 1:10 1:9 1:8
Fig 50: Appendix 1: Establishing Proportions of Quicklime for Stabilization
Possible shrinkage of ‘as
dug’ and sieved soil, in
600mm x 40mm x 40mm
linear shrinkage box mould,
before lime addition.
i) Establishing Initial Quicklime to Soil Proportions
ii) Establishing Initial Lime Putty or Dry Hydrate to Soil Proportions
(Note that double the volume of lime putty or dry hydrate to quicklime is suggested for trial
mixes using lime putty or dry hydrate).
Fig 52: Simplified Appendix 1 Table: Suggested Quicklime to Soil Proportions
Fig 51: Simplified Appendix 1 Table: Suggested Quicklime to Soil Proportions
Trial Powdered Quicklime Proportions toTotal Soil by Volume
Quick Lime : Soil
(3 test specimen cubes per mix minimum)
Shrinkage in mm
Less than 12mm
1:15 1:10 1:8
12-24mm
1:8 1:7 1:6
24-36mm
1:6 1:5.5 1:5
36-48mm
1:5 1:4.5 1:4
Trial Lime Putty or Dry Hydrate proportions to Total Soil by Volume
Lime putty : Soil
or
Dry hydrate : Soil
(3 test specimens cubes per mix minimum)
Shrinkage in mm
Less than 12mm
2:30 2:20 2:15
12-24mm
2:15 2:14 2:12
24-36mm
2:12 2:11 2:10
36-48mm
2:10 2:9 2:8
600mm x 40mm x 40mm
600mm x 40mm x 40mm

2.3.4 Alternative trial mix suggestions:
A different starting point to establish the optimum proportions of quicklime for soil
stabilization is to first determine the amount of clay in the soil sample through use of the
linear shrinkage box test above, then prepare trial mixes based on adding 20% powdered
quicklime to the clay fraction. (ie. th of the clay percentage) for example:
15% clay test 3% quicklime }
20% clay test 4% quicklime } to the total soil sample
This results in a slightly reduced quantity of quicklime proposed for the initial trials,
compared to the linear shrinkage method above.
2.4 Mix Design for Soil stabilisation with Lime - Establishing Mix Proportions:
Mix design, particularly proportioning lime to soil, depends on the combination of soil
content, clay type, particle size distribution and clay proportion of the soil.
Once there is a region where materials of a known and consistent type are available, the
best mix ratios may be repeated indefinitely, after verification by laboratory testing. A mix
design can then be made available that is reproducible for that region.
Mix Design: After the first stage of individually field testing locally available building
materials, select the best quality materials, calculate lime proportions based on the linear
shrinkage test results of the soil, and with reference to Appendix 1 use all information
gained to formulate trial mixes for each building element.
2.4.1 Trial Mixes for Each Building Component
It is recommended that trial mixes for each building element are made in the form of :
BLOCKS: for foundations and wall brick and block mixes (dimensions variable
according to local custom);
DISCS: about 3”diameter x 1”thick for render, plaster and roof finish/roof screed and floor
screed trial mixes;
CUBES: 50mm x 50mm (or 2”x 2”) cube moulds for mortars, floor screeds, brick and block
mixes and 6”x 6”cubes for foundation and slab mixes in addition to their corresponding trial
mix blocks). The moulds are typically made to the above internal dimensions in the form of
3 gang cube moulds from smooth surfaced and oiled timber, for ease of de-moulding.
150mm x 150mm (6”x 6”) cube moulds are useful for larger sample foundation or cob trial
mixes (with larger sized aggregates) for later initial field evaluation laboratory testing.
Test mouldings in steel moulds of successful trial mixes should be made for later
compressive strength laboratory testing of proposed foundation, brick, block and mortar
mixes.
Keep Costs Down - Select a clay content soil that requires minimum lime addition for
stabilisation, or consider modifying the soil (possibly with well graded, sharp sand)
Render and plaster trial mix samples for stabilisation testing are prepared in the form of
discs for soak testing and for permeability testing of both these and also roof and floor
screeds
Note: the Appendix 1 chart recommends that 3 different trial mixes are made for each soil
(mm shrinkage reading), per building element, each with a slightly higher or lower
proportion of lime.
Method: Make a minimum of 3 trial mixes of varying proportions of lime : soil per element:
For example, for a soil of 18mm shrinkage, Appendix 1 proposes 3 trial mixes of varying
proportions (parts of quicklime to soil) for each building element:
1 QL : 18So (3 trial mixes)
= 9 trial mixes, as each trial mix will be in triplicate.
A total of 9 trial mixes will therefore be made for the soil for each building element.
These test mix trials will be in the form suitable for the building component/element for
which the mix is being tested (generally cubes, discs and blocks. See fig 53).
Fig 53: Trial Mix Samples: Make an initial 3 Samples of 3 different mixes as suggested
in Appendix 1 - Blocks, Cubes or Discs
i i i
i
i
i
i i i
i
i
i

2.5 Materials Preparation (before use, in both Trial Mixes and in the Main Work)
2.5.1 Soil Preparation:
Prior to adding lime to soil as a stabilizer, or prior to modifying the soil in any way, the soil
needs careful preparation.
i) Soil Selection
Before selecting the subsoil strata for testing, completely remove all the top layer of soil
(topsoil), which includes all the organic growing matter, as this will not be suitable. See
Section 1.2.4. Dig down into the subsoil which is usually a slightly different colour. The soil
for use in lime stabilized building elements must be sub-soil, or the mixes are unlikely to
produce durable results. First refer to Sections 1.2.5 & 1.2.6 on field testing soil to check if
the soil has enough clay in it to mix with the quicklime for stabilization trials. Inspect
different strata down to about 2m or more and test representative samples from each (fig
54).
ii) Soil Grading
Ideally, dry the soil. Remove all large lumps and stones. These can cause weakness when
making a block and particularly smaller test specimens. The size of aggregate in the soil
should relate to the size of component or building element, ie very fine for plasters and
finishes, but much larger for blocks, and larger still for cob or compacted walling. Break
down the soil lumps into small particles, as the lumps are likely to be clay. Use a sieve or
screen if available, to ensure that there are no stones or insoluble lumps bigger than 5mm
in the mixes for testing.
Fig 54 : Soil Selection
iii) Soil Tempering
For blocks, renders and plasters, temper and mature the soil first, prior to preparing trial mix
samples. If the soil has good clay and sand content, ideally with not less than about 15% clay
for blocks and renders, consider a trial mix of 10 parts of soil, 3 or more parts short chopped
fibre and just enough sprinkled water to make it workable, not wet. For render mixes,
consider adding 1 or more parts of slurried cow dung.
Fig 55: Soil Tempering: Prepare Soil Mixes in Advance, and leave to Mature
Fig 56: Turn the soil and
mix again before adding lime
? ? ?

Thoroughly mix and leave it to stand overnight. This helps the particles to breakdown,
‘mature’, and combine well. Mix again the next day. Thoroughly mix the soil and fibre mixture
again. If too dry, sprinkle water into the mixture so it is damp throughout, but not wet. Add
only small amounts of water until a slightly sticky and lightly moist consistency is achieved.
This mix can be left to mature for a week or more provided it is well covered and not allowed
to dry out (Figs 55 and 56).
2.5.2 Lime Preparation:
Prior to making trial mix samples, the lime will need appropriate preparation and testing for
quality. See Section 1.1.5 to 1.1.9 for details on the preparation methods and testing of
quicklime, dry hydrate and lime putty before use.
Note: All forms of lime must be tested for quality before use.
2.6 Lime Type in Stabilized Mixes :
Soil stabilisation of all building elements can be conducted with all 3 forms of non-hydraulic
lime: quicklime, lime putty and dry hydrate. However, there are best options if these are
available :
Quicklime is preferred generally for all building elements, and specifically for
foundations and blocks;
Lime putty is preferred for renders and plasters, if finely sieved quicklime is not
available;
Dry Hydrate is a secondary choice, and could be used in place of lime putty if it is not
possible to slake the lime to putty, or in place of quicklime if it is not possible to crush
the quicklime.
Note: It is not advisable to use dry hydrate in renders and plasters, as the hydrate may
continue the slaking process within the mix on the wall and may ‘blow’ holes in the
work.
Stabilizing with Different Forms of Lime
Quicklime: When stabilising clay soils, quicklime is best crushed for all building
elements including foundations and block mixes, and as very finely crushed, best quality
quicklime in renders and plasters rather than lime putty. Quick lime is more reactive than
lime putty, but if used for render, it must be very fine powder of the highest quality.
Dry Hydrate is useful when it is not possible to crush the fresh, burnt quicklime, and is
quick to manufacture (but is not recommended for use in renders and plasters).
Lime Putty is better quality than dry hydrate and is best used in low clay or sandy soil or
sand and pozzolan based renders and plasters. The putty provides a wetter, stickier mix
for good workability. If best quality, crushed quicklime powder is not available for render
and plaster mixes, use good quality lime putty.
Hot mixing with best quality quicklime powder is the most efficient method
of stabilizing clay soil
2.6.1 Stabilization of Clay Soil with Quicklime:
Hot Mixing: Best quality, finely sieved quicklime powder is the most effective way to
stabilize clay soils and can reduce or eliminate cracking. Mix fresh, fully reactive dry, crushed
and sieved quicklime powder directly into clay soil (or sand and pozzolan). This is known as
a‘Hot Mix’. (Figs 57 & 58). A hot mix with soil must be used almost immediately. But there
are added health and safety risks. Protect your eyes and bare skin, and wear a dust mask at
all times when using quicklime. Use shovels to mix - do not use bare feet (Fig 58).
The mixing can be done either with all dry materials first, with water added last, or with
pre-wetted (damp) soil or sand. The mix must not be too wet, however, or there will be a
considerable loss of strength and possibly failure of the finished work. Hot mixing with best
quality quicklime is the most efficient method of preparing a mix for stabilizing clay soil
blocks, or making lime plasters, mortars, renders and lime concrete. Before final placing or
compacting, ensure all quicklime has fully slaked in the mix and that there are no unslaked
lime particles left. Check the mix is uniform in colour. Use a quicklime hot mix
immediately, once all the quicklime is slaked (when all the small, sieved lumps of quicklime
have broken down).
Why slake quicklime to lime putty ?
Putty manufacture requires more time and equipment than the crushing of quicklime or
the making of dry hydrate. However lime putty is an excellent method for production of
best quality lime, and storage of fresh lime if the quicklime cannot be crushed and used
immediately. Lime putty, when stored under water, improves in quality over time.
For initial trials as a rule of thumb, about double the amount by volume of dry hydrate or
lime putty would be required in a mix, compared with powdered quicklime, mainly
because of the swelling through hydration of both the putty and the dry hydrate.

The mix must not be too wet or too dry or there will be a
considerable loss of strength and possible failure of the finished work
Fig 58: Use shovels for mixes with lime - Do not use bare feet
Fig 57: Hot Mixing - add minimum water
Fig 59: Proportions of lime to soil and other materials for hot mixing (and all methods of
mixing), will depend on successful Stage 2 test results and how to select proportions
Fig 60: Lime putty can be used to stabilize all building elements, and is particularly
more manageable for those mixes with sand or sandy soil and pozzolans
2.6.2 Stabilization of Clay Soil with Lime Putty
If it is not practical to produce best quality finely powdered quicklime, lime putty is an
excellent alternative, provided it is of the quality recommended. Lime putty may be used
to stabilize all building elements and may be more manageable for mixing earth plasters
and renders, particularly those with sandy soil / sand and pozzolans, ie mixes without the
sticky, binding qualities of clay soils (Fig 60).
The volume of putty however, may need to be up to twice that of quicklime to achieve
similar stabilization. Ensure all mixes with lime putty are uniform in colour before using.

Fig 61: After thorough mixing, mixes with lime putty can be used immediately or
left covered for up to 24 hours before thorough mixing again prior to use
Fig 62: Like lime putty, proportions of soil to dry hydrate may need to be up to double the
volume of quicklime required for stabilization
Mixes using lime putty will benefit from thorough and sustained mixing for a minimum of
20 minutes, and mixes with clay soils may then be used immediately or allowed to sit under
shade for an hour or two before being mixed again prior to use. Keep such mixes damp and
covered and do not allow to dry out. (Fig 61)
2.6.3 Stablization of Clay Soil with Dry Hydrate
Another alternative to using quicklime is to use lime dry hydrate powder, although as with
lime putty, a greater proportion by volume will be required to produce the same result.
Possibly up to double the volume that quicklime would have required (fig 62).
Fig 63: Pozzolans after testing for reactivity, can be added in finely sieved powder form
to low clay soil trial mixes, or sandy soil or sand and other aggregates
Add the fresh lime dry hydrate powder if quicklime powder is not readily available. This can
also be mixed as a hot mix, as outlined above. Ensure uniformity of colour in mixes, and use
the mix immediately.
2.6.4 Stabilization with Lime and Pozzolan
(Stabilization of soil with insufficient clay content for stabilisation, or of sand or sandy
soil)
Crush a crumbling or damaged fired clay sample from broken bricks, tiles, pottery, or other
pozzolanic material, into dust or obtain the dust from a brick works, making sure that it is
brick dust and not earth or ash. Use only the dust that will pass through a very fine mesh
sieve (possibly no. 60 (0.2mm) or as fine as number 230 (63 micron) sieve size. Usually the
finer the pozzolan the more reactive it is likely to be. The burnt clays react with the lime and
may enable it to remain set under water. Wet sieving will be necessary for the finest
material.
How much of the pozzolan is added to a mix depends on how reactive the pozzolan is with
the lime. (See Section 1.4.2: Pozzolanic Reactivity).
Depending on the reactivity of the pozzolan, it can be added to the lime (quicklime, lime
putty or dry hydrate) in an optimum ratio to be confirmed after testing - possibly in the
order of 2 or 3 parts of burnt brick dust to 1 or 2 parts lime putty, or added to a sand : lime
mix to provide a hydraulic set, in the order of about 2 to 3 sand to one lime putty.

In warm and dry conditions, damp down all lime work as often as possible to speed up
the rate of carbonation
High quality thin finishing coats are possible with lime putty and fine sharp sand or marble
dust or other clean, fine and sharp aggregates, and these can be improved further with
polishing. Lime and sand only mixes however, require a far greater proportion of lime than
lime stabilized soil mixes; generally between 2 to 3 sand to one lime.
Note: Unstabilized mixes are not suitable for prolonged exposure to flood, wet or damp
conditions. A well prepared and applied non-hydraulic lime:sand render will withstand wet
conditions over short periods but not continuous saturation or frequent soaking. Mixes
that can withstand continuous wet conditions include lime stabilized soil, lime and
pozzolan and hydraulic lime mixes all of which must be subject to satisfactory test results
before use in the main work. First refer to section 1 on the Field Testing of Materials and
ensure the lime and sand or aggregate and pozzolan are of the quality and fineness
required for best results. The lime may be used in the form of putty, dry hydrate or
quicklime, but for plastering with lime:sand and lime:sand:pozzolan mixes only, lime putty
is preferable because a good quality putty should provide a reliably sound mix, a smooth
finish and good workability. If using sand, a mix with lime putty is easier to apply.
2.7 Curing the Trial Mix Samples
After preparing all trial mix samples based on clay content and suggested proportions of
lime to soil given in Appendix 1, all sample mixes must be properly‘cured’before testing.
i) Curing: Keep the trial mix samples regularly dampened and shaded for 28 days.
Fully cure all trial mixes for 28 days. This simply involves placing the samples carefully on a
flat surface under shade, and keeping them regularly dampened. The humidity and
temperature will determine how often the samples should be dampened, but in very warm/
hot and dry conditions, it is recommended that damping down should take place no less
than 3 or 4 times a day, preferably more. Ideally, in warm and dry conditions, damp down
all lime work as often as possible. This could speed the rate of carbonation and the
hydraulic set during the curing process. If not personally curing the samples, ensure that the
task is delegated to a named responsible person and well recorded.
ii) Carbonation and chemical set:
Referring back to the Lime Cycle, it can been seen in the last stage of the cycle that that the
lime needs to be fully cured. It is essential therefore that carbonation and set in a hot
country is assisted. This is critical for the mix to achieve full strength and perform properly.
The re-absorbtion of water is important for both carbonation and the chemical set of
hydraulic mixes. The presence of moisture as well as high temperatures assists the chemical
setting process. The more the mixes are dampened, then evaporate and are dampened
again, the faster the curing process is likely to be, and the more successful the set.
If well shaded, the mixes are less likely to dry out too quickly. If the mixes are not tended
and dry out rapidly, the strength gain will be reduced or possibly lost completely.
2.6.5 Unstabilized Mixes - Non-hydraulic Lime with Sand, or with Sandy Soils, without an
added Pozzolan
High quality plasters and renders can be obtained with lime putty and sand only, or
sometimes lime and sandy soil.
Moist and warm or hot conditions assist the chemical set which produces compounds
that remain stable under water, ie are hydraulic
To confirm that the correct proportion of lime has been added for stabilization, soak test all
trial mix samples:
Soak test all cured samples (blocks, discs, cubes) of all test mixes and all cube moulds by
immersion in water.
Keep them under water for as long as required, certainly for the maximum anticipated
length of continuous flood conditions, or for as long as possible.
Monitor regularly to check on stabilisation, and that no test sample or part of a sample has
dissolved in the water, and remains strong in compression.
2.8 Soak and Strength Tests
Field Testing of Trial Mixes after 28 Days Curing
The Immersion (Soak) Test is the most important field test for confirmation that trial mix
proportions will produce a material that will remain stable under water.
It is essential to test the trial mixes to confirm the optimum mix design before use in the
main work and to ascertain whether the soil has been sufficiently stabilized.
2.8.1 The Soak Test (Immersion Test) - for stability under water
No mix can be classified as‘lime stabilized’without successful immersion (soak) test results
and compressive strength results.
ALL cured building element trial mix samples must be soak tested: foundation blocks and
cubes; wall blocks and cubes; mortar and floor screed cubes; render, plaster, floor screed
and roof screed discs.
The soak test is the most important test for all trial stabilized mixes designed for flood
resilience
Fig 64: The Soak Test: This is test for stability in wet or flood conditions.
Soak all cured sample mixes for as long as required and monitor regularly

If after the required period of time (usually the anticipated worst flood duration or three
months, whichever is the greatest), the samples have remained stable under water -
especially those with the least proportions of lime - consider making further trial mixes with
less lime. Such further mixes would aim to reduce the lime proportion further each time, to
establish the minimum amount of lime required to achieve full stabilization.
Monitor Results
The soak test indicates how well a block or any lime stabilised building element may last
without dissolving in rain and flood conditions or underground, in rain and flood conditions
or under water. Record the mix used and clearly reference the samples under test. Ensure
the references to the different mixes under test are permanent and do not wash away while
the samples are soaking under water. Place test samples including wall building blocks and
foundation blocks under water for a minimum of one month or longer. The best mixes can
be tested for up to a year or more. Verification by laboratory testing should confirm that
fully stabilized mixes should not dissolve at all (and should pass the wet strength test, where
compressive strengths of between 1.5 N/mm2
and in excess of 3N/mm² after 28 days curing
should be achieved). Arrangements should be made for laboratory testing of compressive
strength at 2 months, 6 months, one year and 2 years.
2.8.2 The Step Test - Field Test for Compressive strength
Ensure the block to be tested has been cured properly for 28 days. Perform the step test.
Method: Place one block lengthways across the gap between two lower blocks also placed
lengthways. Ensure the top block for testing only overlaps the lower support blocks by a
maximum of 2 inches either side. (The wider the gap the better. This should not be less than
300mm for blocks and 150 for bricks). Find someone with good balance to stand on one
foot in the centre of the block so it takes the full weight of the person (fig 65).
If a common size block splits when overlapping the supporting blocks by about one or two
inches either side, apart, then block is not strong enough. It may need more time to cure,
there may be defective materials or an unsatisfactory mix ratio, or it has not been made well
enough. If this occurs, the reason for the failure should be determined, rectified and the
subsequent block tested again.
It may be possible to make successful modifications to trial mixes with lower proportions of
lime to reduce the amount of lime required for a mix whilst retaining sufficient strength and
stability for purpose. The lower the lime proportion required for stabilization, the lower the
cost of construction.
If the blocks in the water start to dissolve, but were strong in the step test, they have not
been adequately stabilized and should not be used where they may be subject to flooding.
The reasons for failure should be established and defects corrected with further testing. It
could be that the proportion of lime in the mix needs to be either increased or reduced, or
the clay soil is unsuitable for stabilization, which should have been determined during the
testing of mixes for stabilization described in Section 2.2 and Appendix 1. Unstabilized
blocks however, could be used to build above the flood line. These could be finished with a
good stabilized render, and a good roof and overhang that prevent water penetration.
Note: It is not always the case that the higher the lime proportion in a mix, the greater the
stabilization. Possibly a lower lime proportion will stabilize a mix more effectively than a
higher one. The optimum lime proportion for stabilisation of different soils and mixes
varies, which is why a range of field test mixes is advisable.
2.8.3 Comparative wet compressive strength Field Tests & requirements
Compressive Strength :
John Norton4
suggests that dry compressive strength values for compressed unstabilized
mud brick are at least 1.5 N/mm2
, (220 psi) after one month drying, depending on climate.
Compressive strength values for stabilized soils are given as wet strengths, since this is the
critical strength condition. These values should be at least half the dry strength value. A
suggested wet compressive strength minimum for internal partition walls is 0.7 N/mm2
(100
psi) after one month.
Lime and lime stabilized compounds develop their strength slowly and to allow for this over
the longer term, additional compressive strength tests should be carried out at 2 months, 6
months and 1 year with the same mix. It may take 2 years or more to reach full strength.
However, experience with well prepared lime stabilized soil mixes in 2013 and 2014 in
Pakistan has shown that field tests with hand held concrete penetrometers indicate
confined compressive wet strengths of over 4 N/mm² (600 psi) after 1 month curing. Similar
strengths have been achieved with some mixes after several months under water, some
over one year under water, many of which are still soaking.
Refer to Appendix 8 notes on Greater London Council 1972, London Building Byelaws and
comparative compressive strengths including field test results achieved in Pakistan.
Fig 65: The Step test

2.8.4 Permeability Field Testing
Trial sample discs of render and floor & roof screed mixes can be subjected to a simple
comparative liquid permeability field test to assess how long the sample can resist moisture
penetration and saturation. If the discs are uniform in size and depth (about 1” thick), the
cured discs can be placed inside a standard funnel, the sides sealed with a water resistant
sealer (usually allow 24 hours for the sealer to set) and the funnel placed in the neck of a
dry jar (fig 66). A consistent head of water for each sample is gently poured on top of the
sample so it is fully submerged. Note the rate of seepage at what duration over hours, days
or weeks, and assess whether the mix is suitable for location, use and climate, and compare
alternative mixes.
2.9 Recording Mix Ratios:
Ensure each test sample is clearly marked or labelled with the detail of its mix. Mix ratios can
be scratched carefully into the surface of a mix before it has dried, or if labelled, a
permanent marker is essential.
Mixes are generally written as a ratio showing the number of parts, starting with lime, then
soil, then sand, then pozzolan followed by fibre and cow dung.
For the soil stabilisation programme in Southern Pakistan, the ratios for the main
materials are written below (the list is not exhaustive and marble dust or grit etc can be
added):
Fig 66: Permeability Field Testing
2.10 Test Mix Recording - Test Record Sheet
Before undertaking any tests, prepare all recording material including a test record sheet
and permanent markers. Meticulous recording of all stages of testing is essential, including
dates, locations, depths, tests undertaken, durations, results & name of tester. Particular
regard should be paid to the mix materials and proportions, quality of the lime used, exact
location of the soil and other materials used in a trial mix, monitored curing conditions and
the soak test results. Preferably support all records with photographic documentation.
See Appendix 7 for an example of a test record sheet.
When soaking several trial mixes in one bucket, ensure that each sample can always be
identified, for example a mix written in permanent marker onto the surface of a block, cube
or disc may eventually become unreadable if the surface of the sample dissolves beyond a
few millimetres! Place clearly marked sample discs or cubes into transparent plastic bags,
and label the plastic bags with permanent marker to avoid confusion and to soak more
samples in one container.
Abbreviation Name of material
QL Quicklime
LP Lime Putty
DH Dry Hydrate
So Soil
RS River Sand (soft)
HS Hill Sand (sharp)
Cr (Gravel) In Pakistan, gravel is known as Crush when it is crushed stone
Pozzolan:
BBD Burnt Brick Dust (Pozzolan)
RHA Rice Husk Ash (Pozzolan)
Bs (Bhoosa): Fibre: In Pakistan the short chopped wheat straw is called Bhoosa
CD Cow Dung
For example :
Parts written as: translate as :
1 QL : 10 So 1 Quicklime to 10 Soil
2LP : 2BBD: 6HS : 3Bs :1CD 2 Lime Putty : 2 Burnt Brick Dust to 6 Hill Sand
to 3 Bhoosa to 1 Cow Dung
2DH : 2RHA : 16So 2 Dry Hydrate to 2 Rice Husk Ash to 16 Soil

LIME STABILIZED CONSTRUCTION LIME STABILIZED CONSTRUCTION 90
Content Stage 3 - MANUFACTURE AND CONTINUED TESTING
OF LIME STABILIZED BUILDING COMPONENTS
3.1 Introduction
3.2 Lime Stabilized Foundations
3.2.1 Lime Concrete & Stabilized Soil
3.2.2 E ca ation
3.2.3 Compaction
3.2.4 Minimum Water Content
3.2.5 Stabilization of arious Soils & ariations in Treatment
i) Clay Rich Soils
ii) Clayey Soils with a Little Sand
iii) Sandy Soils
iv) Gravelly Clayey Soils
v) Gravelly Sandy Soils
vi) Silty Soils
vii) Saline Soils
viii) Large Aggregate
3.2.6 Suggested Lime Stabilized Foundation Options
i) Compacted Lime Stabilized Soil Foundations for Clay Soils
ii) Stone (or Brick) Foundations with Hydraulic Lime Mortar
iii) Brick, Block or Stone Foundations
iv) Hydraulic Lime Concrete Foundations
a) Mix for Lime Concrete Foundations
b) Protective Plinth (or ‘toe’) of Lime Concrete
Lime Stabilized Bricks and Blocks
3.3.1 Correct Moisture Content
i) Ball Test
ii) Bar Test
3.3.2 C ecking t e Block Mi
3.3.3 Oiling t e Block Mould
3.3.4 Filling t e Block Mould
3.3.5 Compressing t e Mi
3.3.6 Remo ing t e Block
3.3. Care in andling t e Block
3.3. Curing Blocks
3.3. Stacking Blocks
3.3.1 Final Placing of Blocks - Dipping blocks in ater before use
3.3.11 Field Testing Blocks during t e Main Work
3.4 Lime Stabilized Eart Mortar
FIELD TESTING: STAGE 3 - BUILDING COMPONENTS
3.4.2 Setting Time Tests
3.4.3 Mortar Application
3.4.4 Dampen Walls
3.12 Finis es Lime Stabilized Decoration and Lime as
3.12.1 Decoration
3.12.2 Lime as as a Paint
3.12.3 Lime as Preparation pplication and ftercare
i) Wall Preparation for Limewash
ii) Mixing External Limewash
iii) Limewash Application
iv) Second and Subsequent Coats of Limewash
v) Durability of Limewash
vi) Limewash Aftercare
3.13 oof Finis es
3.4.4 Dampen Walls
3.5 Lime Stabilized Cob
3.6 Lime Stabilized Rammed Eart
3. Lime Stabilized Wattle & Daub Loqat
3. .1 T e Wattle
3. .2 Daub & Render
3. Sample Render and Plaster Panels
3. Lime Stabilized Plaster For Internal Finis es
3. .1 Plaster Mi es
3. .2 Clay Ric Soils for Lime Stabilized Plaster
3. .3 Sand or ery sandy soil for Lime Stabilized Plaster
3. .4 Protection & Curing
3.1 Lime Stabilized Render For E ternal Finis es
3.1 .1 Selecting Materials & Preparation
i) Background Key to Walls & Plinth
ii) Brush down the Walls
iii) Prepare Sun Shading
iv) Wet the Walls
v) Lime Quality
vi) Storage & Protection of Mixes
3.1 .2 Render Application
i) Method
ii) Closing Crack
3.1 .3 Render Trial Mi es
i) Additional Durability
ii) Trial Mixes for Lime Stabilized Clay Content Earth Renders
iii) Fibre Reinforcement
iv) Trial Render with Clay Rich Soil
v) Trial Render with Lime Putty, Pozzolan and Sand
3.1 .4 Trial Render and Plaster Panels
3.11 Lime Stabilized Floor Screeds
3.11.1 Floor Finis es
3.11.2 Screed & Pit Linings for Water Resistance
3.11.3 Suggested Trial Mi es
3.11.4 Protection & Aftercare

Stage 3- Lime Stabilized Building Components
3.1 Continued Testing of Successfully Tested Mixes in the Main Work:
To establish best mixes for building components, the field testing of the trial mix samples as
set out in Stage 2 should be conducted before starting the main work on site (primarily the
soak test, then all other appropriate tests: compressive strength test and permeability
testing where relevant). Successful mix proportions based on the first and second stage test
results are used for the third stage of testing, which is to test all components and elements
before commencing full production and construction. This is mainly to check that the bulk
soil supply for the main work is identical to the soil samples used for testing mixes in the
Stage 2 tests, and the production process gives the same satisfactory results. Similarly, all
final building elements produced must continue to be tested during the course of
manufacture and construction for consistency of quality. Tests should be carried out on all
elements at regular intervals, for example for block making, test at least 3, preferably 5 of
the first 500 blocks made, and test mixes at intervals for up to 2 years for both stability and
dry and wet compressive strength. It is likely that lime stabilized work will continue to
increase in compressive strength over 2 years.
3.2 Foundations and Lime Concrete
3.2.1 Lime Concrete and stabilised Soil for Trench Footings
Strong foundations are important for all buildings and essential for the construction of
flood resistant buildings. In flood prone areas the foundations are likely to be saturated
longest of all the building elements. Materials and mixes used for foundations therefore
need to be thoroughly tested to ensure that they do not dissolve under water before being
used for the main work.
3.2.2 Excavation
Dig the foundation trench. Remove the topsoil, dig a trench to the size of the foundation
required to support the superstructure. Compact the loose ground at the bottom of the
trench before placing the foundation material, by ramming and tamping it down well and
damp down the bottom and sides of the excavation.
Fig 67: Digging the Foundations and
compacting the ground
The shape and size of foundations will vary with local conditions. If in doubt about this, the
advice of an engineer with practical experience of earth building should be sought. As a
general rule the foundations should be taken down to a solid base which may be found
either near to or at any depth below the surface. The ground conditions in towns and
villages should be carefully examined for accumulated landfill which should be avoided or
taken well into account in the foundation design. Recently disturbed land including that
used for agriculture is similarly suspect and foundation design and location need to be
considered accordingly.
Minimum water should be introduced to stabilized soil trench foundations and footings
and maximum compaction applied when placing them (figs 68 and 69). If solid strong
materials are available like rock, stone, broken brick, large gravel and other inert material,
these can be incorporated as aggregate in trench foundations provided that they are well
compacted and bound together with fully stabilized soil or a hydraulic lime mortar.
See 3.2.3 and 3.2.6 for examples of foundation options and figs 70 and 72.
Fig 68: Laying the Foundations, with a
workable, but as dry a mix as possible

3.2.3 Compaction
Good compaction is required for a stabilized soil foundation so the foundation trench
should be shaped to accommodate this (fig 69). Trench foundations are regular in shape
and an advantage of compacted stabilized soil footings is that the excavation needs no
further work or backfilling. In addition, the sides of the trench act as shuttering. As a general
rule, subject to structural engineer’s advice, the trench should be centred on the wall it is to
support and be at least twice its width. It is essential that the mix used for lime stabilized
soil foundations passes the soak and strength tests first, before use in the main work.
It is essential that the mix used for lime stabilized soil foundations passes the soak and
strength tests first, before use in the main work
Fig 69: Good compaction is essential for foundations
The advice of an engineer with practical experience of earth building should be sought
where there is any doubt about foundation design (depth and width).
3.2.4 Minimum Water Content
Generally, but particularly for stabilized and compacted earth construction and
foundations, use as little water as possible in the mix, only sufficient to make it workable.
The mix must be damp but dry enough to compact hard immediately after placing. If the
mix is too wet, it will be weakened, and good compaction will not be possible. This also
applies to all compacted earth building elements such as compacted blocks and rammed
earth walls. Following compaction ensure that the mix is thoroughly cured by shading and
damping down a minimum of three times a day for preferably, four weeks. Keep it covered
with damp cloth or sacking if possible.
Fig 70 - Foundation Option 1

3.2.5 Stabilization of a Variety of Soils for Foundation Use, and Variations in Treatment
Generally allow for treating different soils in different ways for stabilization as summarized
below and subject to satisfactory Stage 2 test results. In all cases, as outlined above, mixes
for foundations should incorporate the minimum amount of water and be well compacted
when placed.
i) Clay Rich Soils
Use quicklime powder for the soil stabilization of foundations. Dry hydrate powder or lime
putty may be used as an alternative, but stabilization is unlikely to be as fast or effective.
ii) Clayey Soil with a Little Sand
These may be stabilized as for clay rich soils. For foundations, they might be improved by
the addition of sand, gravel and stone aggregate, again subject to testing.
iii) Sandy Soils
Use pozzolan and lime, or hydraulic lime mixes to improve the hydraulic set and water
resistance. Strong hydraulic sets are required for foundations in wet or flood areas.
iv) Gravelly Clayey Soil
As for clay rich soils, use quicklime powder.
v) Gravelly Sandy Soils
As for sandy soils, use hydraulic lime or lime with pozzolan.
vi) Silty Soils
High silt content soils are not suitable as a building material. Silty soils cannot be used
without major modification and the addition of substantial quantities of sand and/or clay. It
is important to ensure that if soils that include silt are modified, mixes are subject to
thorough testing and only used if the test results are satisfactory. A soil’s silt content should
not exceed 20% for modified and stabilized earth mixes and 6% for lime : sand (and
lime : sand : pozzolan) mixes.
vii) “Salts”
If there is failure of field tests due to very high salt levels in the soil, the soil should not be
used. Laboratory testing analysis of the soil is recommended. A few possibilities causing
defects would include: acid pollution, calcium nitrate, calcium sulphate, expansion of
crystals, sodium sulphate, tricalcium aluminate, sodium chloride, calcium chloride, sodium
hydroxide, sulphite and sulphate nitrates, nitrous acid, nitric acid, ammonia, nitrites and
nitrates.
The presence of sufficient quantities of any of these may prevent set, or cause a lack of
adhesion of the soil at a later date. Some chemicals that may have a detrimental effect on
lime stabilized soil occur naturally from weathered rocks and some may well be due to the
application of fertiliser. Most can be transported by water.
viii) Large Aggregate
The addition of more stone to the mix, or all stone or burnt brick with hydraulic lime mortar,
are possible foundation materials subject to local availability and cost.
A number of materials are suitable for building foundations but various forms and
construction methods appropriate for the chosen material need to be considered. Materials
most likely to be locally available are stabilized soil, fired brick and stone (fig 71).
3.2.6 Suggested Foundation Options
i) Compacted Lime Stabilized Soil Foundations for Clay Soils
a) A clay soil which includes sand and gravel as well, is likely to give the best results.
Either mix the ingredients dry first, or mix the quicklime into a damp, tempered and
pre-mixed soil, then add the minimum amount of water to achieve workability.
Consider additional and larger sizes of gravel subject to availability and further
testing. Mix very well until an even colour is achieved. Before the main work, test a
block made with the mix for at least one month to ensure it is stable under water. All
the quicklime powder used should be fully reactive, fresh from the kiln and there
should be no under burnt or over burnt material for best results.
Fig 71: Likely locally available materials for foundations in Southern Pakistan:
lime, clay soil and sand and aggregates or lime, pozzolan, sand and aggregates

b) Place and compact the mix in the trench in a series of layers, each compacted layer
about 150mm (6”) deep, and ensure each layer is compacted well. See note above
about using minimum water in the mix.
c) Level the top layer flat and ensure that it is level at the top of the finished foundation.
Shuttering could be used to take the side of the foundation trench up higher to form
a plinth at the base of the wall.
d) Cure the lime concrete foundations for a minimum of two weeks by protecting them
from hot sun and from rain. Keep them humid, by covering with wetted sacks or
tarpaulin and damp down regularly.
e) Examples: typical lime concrete trial mix samples still stable under water after 4
months immersion. See table below.
ii) Stone (or Brick) foundations with Hydraulic Lime Mortar
If strong stone is available it will make a good foundation particularly if the stones are
mortared together. This can be with a hydraulic lime and sand mortar, a non-hydraulic lime,
pozzolan and sand mix or a lime stabilized soil mortar. Foundations can also be made with
well burnt clay bricks and hydraulic lime : sand mortar (Fig 72: Foundation Option 2).
iii) Brick, Block or Stone Foundations
If bricks, blocks or stone are selected for foundations where there is flood risk, clearly they
will need to remain stable under water. Unstabilized earth bricks or blocks should not be
used. Bricks, blocks and mortars of lime stabilized soil should only be used after fully testing
to ensure that the mix will remain stable under water and pass the wet strength test. This
also applies to units made of any other material including fired brick.
Note: Engineers’ soak tests in Northern Sindh 2014, compared lime stabilized blocks with
Class B fired bricks (softer than Class A, and slightly cheaper, so are common in building use
in local flood affected villages). Class B burnt bricks lost 30 - 40% of their mass through
dissolving in water after only 5 days immersion. The lime stabilized blocks remained stable
under water for many months.
Unlike a trench footing, foundations using smaller units like bricks, tend to need a wider
excavation for adequate stability in order to spread the load evenly and provide sufficient
room in which to work. After building the foundation the excavation has to be backfilled.
Attention then needs to be given to avoiding uneven levels or depressions which would
encourage water to remain close to the base of the building. It is important to ensure that
falls and compaction of the ground encourages all water to drain away quickly from the
wall.
Consider raised ground levels, good falls, bund walls and drainpipes or channels to
encourage rapid water run off.
John Norton recommends that unless specific requirements suggest a different approach, a
foundation (which is composed of individual units) should spread out to an angle of 60° at
its base tapering to the wall’s width at the top. This would be over three or four courses
which must be well bonded together and laid in a hydraulic mortar.
Fig 72: Foundation Option 2: Stepped Block, Brick or Stone Foundations
The advice of an engineer with practical experience of earth building should be sought
where there is any doubt about foundation design.

iv) Hydraulic Lime Concrete for Sandy Soils
a) Mix for Lime Concrete Foundations
b)
Fig 73: Protective‘toe’construction of lime stabilized soil or Iime concrete
Protective ‘Toe’ or Plinth of Lime Concrete - a common design feature in Southern
Pakistan for additional flood protection
Lime concrete is also suitable for a raised plinth or‘toe’at the base of walls (shuttering
may be needed). After the walls are built and cured, or when building the walls, an
additional ‘toe’ or plinth of lime concrete, lime stabilized soil or rendered lime
stabilized blocks will help further protect the base of the wall from flood damage (fig
73).
Mix the dry ingredients first and subject to test results for the mix, allow for 2 to 3 parts
brick dust to 2 to 3 parts lime putty (or 1 to 2 parts quicklime): 4 parts sharp coarse
sand and 6 to 8 parts gravel. If crushed stone is available this could possibly be added
to the mix, subject to testing. Mix well, bring to workable consistency and place in
foundation trench.
Compact all the layers well, each at approximately 150mm deep as described in 3.2.3
above. Laboratory testing of this mix prior to use is advised as above, as is laboratory
testing of all mixes prior to use if at all possible. If available, a hydraulic lime could be
used instead of the brick dust pozzolan and non-hydraulic lime putty.
Note: Toe construction may not be necessary if all the building components from the
foundations up are fully lime stabilized. However, such a ‘toe’ could offer additional
protection from high impact flood water from hills or mountainous run off and surges for
example.
3.2.7 Curing
Foundations and plinths, like all lime stabilized work require proper curing conditions to
assist strength and hydraulic set. Keep all new lime work dampened and shaded from
sunshine and rain for as long as possible, preferably not less than four weeks, before
building off them.
Fig 74: Keep all foundation work very well cured for maximum strength and hydraulic set

3.3 Lime Stabilized Bricks and Blocks
Refer to Stages 1 and 2 for establishing suitable materials and mixes for lime stabilized block
making. Allow for the addition of chopped fibre to hand compacted block mixes, in the
order of 10% or more by volume, subject to testing, to minimise cracking and to strengthen
them for handling.
Proportions will be finalized after Stage 2 testing, but for an initial trial for brick and block
mixes, allow for adding dry, crushed and finely powdered best quality quicklime to the
clayey soil in the proportions of about 1 part quicklime to between 10 and 20 or more parts
soil plus fibre, subject to testing for clay content. Refer to Appendix 1 for trial mix
proportions.
An alternative to using quicklime is to use lime dry hydrate powder, although a greater
proportion by volume will be required to produce the same result. Possibly up to double the
amount that quicklime would have required. The optimum amount of lime for stabilisation
can be determined by field testing as set out in Stage 2.
Together with Stage 1 tests for lime reactivity, refer to sections 2.2 and 2.3 on proportions of
quicklime and field test methods to determine the optimum amount of quicklime to add to
the soil.
For block making, leave the mix to complete the slaking process before compacting it in a
mould (when all the small, sieved lumps of quicklime have broken down). Use a shovel to
turn the mix over where preliminary dry mixing is preferred. Do not use bare feet. The mix is
caustic and can burn. (Fig 58). Keep prepared mixes damp and shaded (fig 75).
Fig 75: Cover any lime putty based mixtures from drying sun or rain,
if they are not being used immediately
3.3.1 Field Tests for Correct Moisture Content:
For good stabilisation and compressive strength, use minimum moisture content and
maximum compaction.
Keep the same size container for water measuring for all mixes, and check consistency
Fig 76: Ball Drop Test for
Optimum Moisture Content
i) Ball Drop Test
Take a gloved handful of moist mixture prepared for block making and shape it into a ball.
With outstretched arm about 1.5m high, drop the ball. If the dropped ball breaks into
between 4 and up to 10 lumps, the mix is probably too wet or too dry with a low clay
content. If it stays in one or two lumps, there is too much water in the mix. If it breaks into
lots of small pieces, but will stay together if squeezed very hard in the hand, it is about right.
(Fig 76).This is very similar to the ball drop test for approximate clay content of soil only, but
in this case it is for checking the moisture content of the whole mix.

ii) Bar Test
Place a large un-compacted ball or shovel full of the mix on the ground. Use a 50cm (1’8”)
long 10mm (¾”) diameter steel reinforcing rod and rest the end of it on the surface of the
mix. Let the rod sink into the soil by its own weight.When the bar sinks in exactly 20mm (¾”)
the water content is right.
3.3.2 Checking the Block Mix
If the mix crumbles when very carefully taken out of the mould (fig 77), this indicates that
the block mix was either too dry, has not been adequately compacted or is not in
accordance with a successful test mix described in Section 2.
3.3.3 Oiling the box mould
Oiling the inside surfaces of the box makes it easier to remove the compressed block
without it sticking or breaking (fig 78). An alternative method to achieve similar results, is to
sprinkle very fine sand onto the inside of the mould before filling.
Fig 77: Testing the newly made block quality
Fig 78: Oiling the block mould
3.3.4 Filling the Mould
Fill the mould with the mix by pressing down firmly with gloved hands, especially in the four
corners of the box (fig 79). Stronger blocks due to greater compacting can be produced on
a range of hand or mechanically driven block making machines now widely available.
3.3.5 Compressing the Mix
Good compaction improves durability and strength of the block. (Fig 80).To improve this for
handmade blocks use a rammer or place a shaped piece of wood or stone on top of the mix
and press it down hard or stand on it to compress the block. Ensure even pressure.
Alternatively, use a compressed earth block making machine such as a Cinva Ram - see
Appendix 3 for more details. Add sufficient mix when filling the box to ensure that the
mould is completely filled to the top with fully rammed material.
Fig 79 - Filling & compacting the block mould
Fig 80: Compact the block mix well, for increased durability and strength

3.3.6 Removing the Block
Take care when lifting the block out of the mould that it does not break or crumble. Lime
stabilized blocks may need the minimum of a week to cure before demoulding (fig 81). It
would be best to carefully lift up the box mould from the new block so that it is disturbed as
little as possible when de-moulding, and de-mould on top of a small supporting board on
which to carry the fresh block, or compact the block directly onto a hard flat surface on
which it may subsequently cured without being disturbed. Hand compacted blocks will
require more fibre in the mix for handling purposes than machine compressed blocks.
3.3.7 Care in Handling the Block
If de-moulding cannot be done in-situ, carrying the block on a board will help to protect the
new block from being damaged (fig 82).
Fig 81: Demoulding the block: Handle carefully for increased durability and strength
Fig 82: Careful handling and carrying of the newly made block (unless the block is
demoulded in situ onto a flat, shaded surface)
3.3.8 Curing Blocks
Assist the curing process by regularly (3 times a day minimum) damping down the blocks
for 4 weeks or longer for lime stabilized blocks (figs 83 and 84). Place on flat, level ground in
the shade, and keep moistened. Use any sheeting material like sacks, cloths, old fertiliser
bags, plastic or grass mats for shading. Plastic sheeting is a good method of covering to
keep in heat and moisture which helps to speed up curing. In hot and tropical climates the
curing process can be accelerated by damping down more frequently (as soon as all
moisture from the previous damping down has evaporated).
3.3.9 Stacking Blocks
After curing in the shade as above, also stack the blocks in the shade. Make sure the ground
is level, or the weight of the stacked blocks may break or bend them, particularly the lower
layers of blocks. Leave gaps between the blocks to allow air to get in (fig 84). Lime stabilized
earth blocks are best given a minimum of 28 days to 6 weeks to harden and cure before use.
Fig 83: Initial curing of blocks : keep shaded and regularly dampened
Fig 84: Stacking, curing and storage of blocks

In hot or mild weather, the longer the curing period for the blocks the stronger they will be,
provided they can be kept shaded and moist. If the weather is colder and wetter, they need
to be stacked for longer still, to achieve the same strength.
3.3.10 Final Placing of Blocks - Dipping Blocks in Water before Use
Dampen well cured and lime stabilized blocks before use. Just before building, dip each
block quickly into water for 10 seconds or lightly spray (fig 85). Do not soak them. If the
blocks are too dry when used they will suck the moisture out of the mortar too quickly, and
the bonding with the mortar will reduce, weakening the wall. Keep all fresh lime mortar
work shaded and damplened
3.3.11 Field Testing Blocks during the main work
Conduct the soak and compressive strength block tests on production mixes one month
after curing them as described in Stage 2, and every month of production for the main work
thereafter, or following production of every batch of 500 blocks. Test at least 5 blocks in
each production run from the first run.
Pre-testing of the mix should be done before starting the main work on production run
materials and blocks and at monthly intervals during the work to check for consistency.
An indication of the compressive strength development can be measured with a hand held
penetrometer.
Fig 85: Dip the cured blocks in water
for 10 seconds before use
3.3.12 Machine Block Making
The preparation of block mixes for Cinva Ram or other block or bulk block making
machinery is similar to the above, but the mix must be drier, and may not require the
addition of fibre. Careful handling of the drier machine block mixes is necessary. An average
production run of 300 blocks per day can be produced by a 2 person team and one Cinva
Ram. Prepare shading material and flat, shaded ground in advance of such production runs
(fig 117).
3.4 Lime Stabilized Earth Mortar
Lime stabilized earth mortar will need to have the same durability under water as the bricks
and blocks for which it is used.The same mix as the blocks can be used for the mortar except
that for fine joints a finer aggregate may be preferred, with a maximum particle size of
about 3mm.
3.4.1 Mortar Mixes Testing
Trial mortar mixes and any variation in the mix should be prepared and tested through
50mm x 50mm cube samples subjected to Stage 2 submersion (soak test) and wet
compressive strength tests. A lower proportion of lime may produce a mortar of lower
strength, but care and soak testing is needed to ensure that the adjusted mix will still
remain stable under water. Discs of mortar, approximately 75mm (3") diameter x 25mm (1")
thick, can also be made up for soak testing after curing. These sample mix discs can also be
used for testing setting times, (see 3.4.2 below) and permeability for the main work (see
2.8.4).
3.4.2 Mortar Setting Time Test
Using either discs of the fully prepared mortar samples or a lime mortar paste, (brought to
the consistency of clay ready for making pottery), the simplest field test is to press a finger
into it at arm’s length. It is considered set when no depression or alteration to its form occurs
until it breaks).
Fig 86: Keep newly laid block walling dampened
and shaded throughout the work, to
stop the mortar drying out too quickly

A more controlled setting time field test may be carried out with a simple piece of
equipment and similarly prepared mortar samples.This consists of a wood or metal rod with
a sharpened point at one end. The point should be sharpened down to one millimeter (0.04
of an inch) square. A standard weight of 300gms (say 10oz) is fastened to the other end of
the rod. Gently lower the point to rest on the disc at intervals, carefully timing them from the
moment preparation of the sample was completed. At first the point will sink into the top of
the sample. The initial set is taken to be the time taken between completing preparation of
the sample and when the sample bears the point of the needle without forming a
depression in the surface.
3.4.3 Mortar Application
If the wall blocks are well made with square and even sides, and are of the same size, less
mortar will be used as they can be laid with thin joints (no greater than 10mm). Use a
straight edge and a level (or plumb bob) to help build straight. To leave a key for render, set
mortar joints back from the face of the blocks by about 10mm to 20mm (¼” to ”).
3.4.4 Dampen and Protect Walls and New Mortar
After placing the mortar, keep the walls under shade and dampened for a minimum of one
week. If the lime in the mortar dries too quickly, it is likely to crumble and fail. It needs to be
moistened over a period of at least a week to help it strengthen. The longer the walls are
dampened and kept in the shade the better, up to four weeks or more. Do not build in direct
sunlight if possible, and erect a screen to shade all the new work from the sun at all times
(fig 87).
If the lime in the mortar dries too quickly, it is likely to crumble and fail
Fig 87: Protect new walls and mortar from drying out too quickly.
Keep shaded and regularly dampened
3
4
3.5 Lime Stabilized Cob
Cob walls are built without formwork on firm usually stone or brick foundations. These rise
1’to 2’(300 to 600mm) above ground level and are no wider than the earth wall above. Cob
walls can be built with parallel or tapering sides (fig 88).
The clay content of the soil should be in the order of 35 to 30% with 20% gravel and the rest
a mixture of fine and coarse sand with fibre (and possibly cow dung). In theYemen and Iran,
high load bearing walls have been constructed this way. A similar method was common for
house building in the south-west of England, in which a quarter of a million cob houses are
still lived in. Cob construction is being reintroduced there and in other parts of Europe
today.
The water content of the mix needs to be higher than that for block making to achieve a stiff
mouldable consistency. The best form of lime to add for stabilizing cob is lime putty. Longer
fibres and coarser aggregate than for block making are also preferable to assist the handling
and in-situ moulding process.
Cob is often an entirely“hands-on”method of building so the consistency of the final mix is
likely to be best judged as correct when it feels right. At the same time it is important that
the correct proportions of lime and clay are selected and tested for stabilization as set out
in Stage 2 testing.
3.5.1 Cob Trial Mixes
Use the proposed stabilized cob mix to make sample cube moulds of 6” x 6” (150mm x
150mm). Test these cubes (soak test and test for both dry and wet compressive strength)
after curing at 28 days, and then again at 2 months, 6 months and 1 year in the same way as
for all building elements.
Fig 88: Cob wall making and shaping

Initial trial mixes for wall blocks given in Section 3.3 could be a starting point for cob trial
mixes, although as above, the mix can be coarser than for blocks, with perhaps additional
fibres (and clay) to improve workability for cob construction.
Trial mixes should also be conducted for assessing shrinkage, as very clay rich mixes
(unmodified through the addition of sand and/or fibre) can result in large cracks in the wall,
which will dissolve under water.
3.6 Lime Stabilized Rammed Earth
Rammed earth walls are built within formwork (shuttering), directly from the foundations or
from a plinth. A prepared mix is placed in the base of the formwork to about 4” depth
(100mm) and then ‘rammed’ (highly compressed) by hand with tampers, or by machine,
before placing and ramming the next layer. Aside from the use of formwork, the main
difference between rammed earth and cob is the consistency of the mix, which is
significantly drier than cob mixes. For effective compression, the moisture content of the
mix should not exceed 7%, which in practice will be similar to the minimum moisture
content block mix required for machine compressed block making, when a handful of
slightly moist mix can hold its form when squeezed (compressed) tightly. Quicklime would
therefore be the most appropriate form of lime to use in stabilising mixes for rammed earth
walling. Throughout France where rammed earth is a widespread and traditional
construction method, it was common practice to ram a lime mix into the corners and
external face of the mix within the formwork, to give the walls additinal durability.
3.6.1 Rammed Earth Trial Mixes
As with cob trial mixes above, use the proposed stabilized mix to make sample cube moulds
of 6”x 6”(150mm x 150mm) and cure and test as outlined in Stage 2 testing (soak test and
test for both dry and wet compressive strength). Repeat these tests at intervals of 2 months,
6 months and 1 year in the same way as for all building elements.
Initial trial mixes for machine compressed wall blocks could be a starting point for rammed
earth trial mixes, although as above, the mix can be coarser than for blocks.
3.7 Lime Stabilized Wattle and Daub (Loh Kath)
3.7.1 The Wattle
Wattle is lightweight interwoven laths, batten or sticks usually woven between firm upright
staves fixed into a frame. They may be plastered on both sides provided they are rigid and
firmly supported. The laths need to be evenly spaced and not too far apart for a good key
to the daub. A term for this construction is‘wattle and daub’and the similar method in Sindh
is known as Loh Kath. It is important that the wattle is closely woven but with sufficient
spaces for the daub to key through, and in a strong structural framework, on which the
daub panels rely for support. The daub and render mixes may be of lime stabilized soil as
described for cob and render (3.5 and 3.8 respectively).
There are many variations of wattle material including alternatives of reeds, grasses and
cane that have also been daubed. Care is needed to avoid using materials that are too light
to give a sufficiently strong support to the daub. Thin reeds and grasses for example, even
when interwoven, are unlikely to be sufficiently robust or durable enough to support a wall
panel for long. Generally this is not a recommended construction method for external walls
unless the framework, wattle and render are sufficiently robust to withstand flood
conditions.
3.7.2 Daub and Render
A mix similar to cob as described above may be used as daub on a wattle framework of
woven timber. The render mix may be improved for daubing by adjusting and possibly
increasing the proportion of clay and fibres. Carry out trials to determine whether a more
sticky and slightly wetter mix than for plaster would assist adhesion to the wattle and daub.
Daub, renders and plasters can be made up into individual test discs and tested the same
way as for mortar samples.
3.8 Lime Stabilized Sample Render and Plaster Panels
Render and plaster finishes are applied to brick, block and other walling backgrounds.
These improve the durability of the walls as well as providing a smooth, hygienic and clean
surface finish.
Conduct sample plaster and render panels to test for finish quality, cracks and adhesion.
Prepare a range of initial trial render or plaster mix panels which could be as small as 250mm
x 250mm, but 900mm x 900mm, or 1 meter square is better, in order to give the best
indication of performance and quality that can be achieved. Ensure they are all applied in
the same manner, with the same minimum moisture content, and are the same dimensions
and thickness. Apply trial render mixes with increasing proportions of fibre, sand (if
available) and possibly cow dung content to establish best mixes for :
a) minimum cracking / shrinkage;
b) good adhesion to the background (ensure the mix is well keyed and firmly applied);
c) robust, hard surface to the first coat, as a solid substrate for the finish coat;
d) ease of application of mix to the wall;
e) a smooth, even surface finish to the finishing coat which is well bonded to the
previous coat;
f) a robust hard surface to the finish coat that does not scratch easily;
g) a clean, polished and attractive finish.
Keep all panels well shaded and cure for 28 days.
Wall preparation should be as outlined in Section 3.10.1 and include a dust free, well keyed
and wetted wall. Hand application of lime stabilized mixes, (as opposed to spray machine
application), should be with float, trowel or gloved hands. Greater compaction during
application improves durability.
Fig 89 - Wattle and Daub

Example of Initial Render and Plaster Trial Mix Test Panel Base Coats : with increasing parts
of fibre (from left to right) and sand (from top to bottom).
Adapt as appropriate - but do not change the lime to soil ratio that was established as
successful for stabilisation in the Soak Test.
Carefully scratch details of the mix proportions towards the top or bottom edge of each
panel. Before drying, one half of selected trial mix panels could be keyed as a base on which
to trial thinner finish coats of render or plaster. A base coat is generally applied about 1 to
2cm thick, and a finish coat only a few mm thick. It may be that a base coat will need to be
applied onto an earlier levelling coat. For levelling and base coats, a fibre rich, clay mix is
recommended. A clay rich mix is likely to have strong bonding properties, and a fibre rich
clay mix can be applied thicker without slumping, can easily take out undulations in the wall
beneath, and will add a degree of thermal insulation. Fine cracks in the base coat can be
filled with the finish coat. Larger cracks should be eliminated, usually through the addition
of more fibre and/or sand parts, through conducting trial render/ plaster panels.
Thin finish coats may require fine sharp sand and/or marble dust to add a degree of
robustness for a harder surface finish, and if trials are conducted with fibre, the fibres should
be finer than those for the body coat, sieved as fine as possible.
I
N
C
R
E
A
S
I
N
G
S
A
N
D
P
A
R
T
S
An example
Lime and Soil
Base rial ix
as calculated
for a particular
soil, through mm
shrinkage and
Appendix 1
eg: 1LP : 6So
1
1LP : 6So : 1B
2
1LP : 6So : 2B
3
1LP : 6 So : 3B
ETC
1
1LP:6So:1HS 1LP:6So:1B:1HS 1LP:6So:2B:1HS 1LP:6So:3B:1HS
2
1LP:6So:2HS
1LP:6So:1B:2HS 1LP:6So:2B:2HS 1LP:6So:3B:2HS
3
1LP:6So:3HS
ETC 1LP:6So:1B:3HS 1LP:6So:2B:3HS 1LP:6So:3B:3HS
1
1
1
1
INCREASING FIBRE PARTS (Bhoosa)
Note: It may be practical to prepare render and plaster discs of the various render mixes at
the same time as the trial render panels, or discs can be made from selected robust, crack
free and well bonded, successful trial panels. As detailed in Stage 2 testing, discs are to be
cured for 28 days prior to soak testing, to test for the stability under water of the render and
plaster mixes.
If a low clay soil or sandy soil or sand forms the base, initial trial render panels in the region
of 1 1LP : 2 or 3 Sand : 1 or 2 Pozzolan could be trialled, with fibre parts from one, through to
three, subject to Stage 2, Soak Test results. (Hill Sand is likely to be better than River sand as
it is sharper and better graded, although depending on availability and cost, tests can be
conducted with both or a mixture).
3.9 Lime Stabilized Plaster (for Internal Finishes)
3.9.1 Plaster Mixes
Well burnt, fully reactive and finely powdered quicklime is the first choice as a stabilizer for
earth plasters, but as a second choice, well matured lime putty is a good alternative. In many
cases putty will be preferable due to the difficulty of obtaining finely powdered quicklime
of sufficient quality. (Well matured means lime putty that has been allowed to settle out in
the settlement pit for at least 3 weeks to 3 months or longer, and is of correct density).
Screening out or sieving to remove lumps from the mix is important for good quality
renders, plasters and mortars. Recommended sieve sizes are given in Appendix 4. For finer
finishing coats, finer aggregate sizes will be necessary. Dry hydrate is not recommended for
renders or plasters as slightly over burnt particles may be subject to late hydration and may
continue slaking on a microscopic level in the mix, and expand leaving holes in the work
(‘pitting and popping’) or in severe cases, complete failure.
3.9.2 Clay Rich Soils for Lime Stabilized Plaster
If the selected sub soil layer from the trial hole is sticky when wetted and has a high clay
content (see field tests in 1.2.5), allow for a mix of between ten to twenty parts soil with one
part of powdered quicklime subject to Appendix 1 and results from the trial plaster panels.
(Para 3.8), plus a little water until there is a sticky plaster.The results of the trial render panels
will determine the optimum fibre content (Figs 89 and 90). Before mixing, the clay soil
should be first dried and sieved to remove any gravel or stones over 5mm in diameter for
the first coat, and 1mm for finishing coats. Fibres should always be incorporated and well
distributed in the mix for the first (base) coat. Assess optimum parts of fibre through testing
in the sample render panels.
Fig 90 : Add fibre for
Tensile Strength

Test the plaster by making samples, curing them for one month and then immersing them
in water for another month to ensure that the mix is fully stabilized before commencing
with the main work. Additionally, make trial plaster panels as outlined in 3.8.
Always prepare the background wall surface with a good key. (See 3.10 for more detail).
Trowel on the plaster firmly, one or two centimetres (3/4") thick to the pre-dampened wall
surface. In preference to only one coat, two or even three coats of plaster or render will
enable improvements to be made to the final finished surface, provided the previous coats
are fully cured, well keyed, and firm.
3.9.3 Sand (or very sandy soil) for Plaster
If the subsoil is not clay rich but very sandy, it may still be possible to use lime to make a
flood resilient plaster.
Lime in all its forms has a long history of being used with sand only for plasterwork, which
has achieved the highest quality. However, this does not give a hydraulic set. Lime putty and
sand only is suitable for internal plasters that will not be subjected to flooding.
Hydrated hydraulic lime powder (not currently available in Pakistan), or crushed
non-hydraulic quicklime or lime putty together with reactive pozzolan can be used with
sand aggregates for a plaster to resist wet conditions.
Artificial or natural hydraulic lime (not readily available in Pakistan at present) with sand
only, can be used for external renders as an alternative to lime stabilized clay soil when
flooding is of concern.
Suggested Trial Mixes Subject to Testing:
When clay soil is not available, carry out some alternative trial mixes. Refer to calculating
proportions as set out in 2.2 for estimating trial mixes for testing. Subject to soak testing,
and to trial render panel results, initial trial mixes for a sand or very low clay content soil
could be:
i) one part of finely crushed, reactive quicklime powder, or 2 parts lime putty plus 3
parts finely sieved pozzolan, to 4 parts or more of sandy soil, and just enough water
to make a sticky plaster plus fibres. All subject to testing.
ii) one part finely crushed best quality quicklime powder to two parts finely sieved
burnt brick dust, with 10 to 20 (low clay content) subsoil, one part cow dung slurry
and 2 parts short fibres. Mix well. Testing before use is essential as above. (Fig 91).
iii) 2 parts of well crushed fine, good quality quicklime powder and 4 to 6 parts finely
sieved burnt brick dust, subject to pozzolan tests, with 6 – 8 or more parts sandy
subsoil, one part cow dung slurry and 2 parts short chopped straw, all ingredients
subject to pre-testing. An alternative to the quicklime powder could be 3 or 4 parts
lime putty.
Note the mix variety above, which gives an indiction of the range of initial trial mix testing
that should be undertaken to determine the best mixes for stabilisation, using least amount
of lime.
An agricultural back pack sprayer with an adjustable nozzle for fine spray, is a quick and
efficient method of evenly wetting the walls, blocks and all lime stabilized work
Fig 91: Subject to testing, a trial mix for low clay soils could be :
1QL (or 2LP) : 3 finely sieved pozzolan : 4 or more parts of sandy soil, plus fibres
and just enough water to make the mix sticky and workable
?
?
? ?

3.9.4 Protection and Curing
During plastering (and rendering) and for at least two weeks but preferably four weeks after
application, keep the plaster or render mix lightly dampened. Gently flick or spray with
water to lightly moisten the walls about 3 times a day minimum, and keep shaded with
wetted sacks, cloths or plastic sheeting. Good curing will assist in strengthening the render
against monsoon rain and flood damage. (See fig 116 for an illustration of an agricultural
back pack sprayer which offers an efficient method of evenly and quickly keepng walls
dampened).
3.10 Lime Stabilized Render (For External Finishes)
3.10.1 Materials Preparation
See suggestions for initial trial mixes below in to 3.10.3 v) and vi) and above in 3.9.2 and
3.9.3
Preparation:
i) Background Key to Walls and Plinth (Fig 92 The walls and plinth may be rendered
with a similar mix to that used for plaster, but the aggregate could be coarser to
make it harder wearing. A good key is important and may be provided by either:
a) Leaving the mortar between blocks set back from the face or
b) Raking out the joints or
c) Scratching or roughening the whole surface.
Fig 92: Preparing the background of the wall by sratching a‘key’into the
surface, and by raking out the joints
ii) Brush Down the Walls
Brush down to remove all loose debris and dust. Renders will not stick to dusty surfaces, and
need a solid clean background (fig 93).
iii) Prepare Sun Shading
Prepare protection (reed mats, sacking, large cloths or sheets) ready for shading the walls of
the building from direct sunshine (fig 94a). This is very important because the lime in the
render mix needs to be kept moist whilst it cures, hardens, and continues to carbonate over
several weeks to achieve a sufficiently robust finish.
Fig 94a: Prepare shading material in advance
Fig 93: Brush walls to remove dust and debris

Give the greatest protection to those walls that will get most of the sunshine, or most of the
rain. Attach the shading firmly to the eaves, as it will need to stay in place for one month.
Keep the shading materials well away from the walls so the render work is not damaged and
can be damped down regularly.
iv) Wet the Walls
Wet the walls thoroughly at least one hour before rendering (fig 95). Then wet them lightly
again just before rendering. Render will not stick to dry dusty surfaces or surfaces that are
too wet. If the walls are not wetted, they will take the moisture out of the render too quickly
and it may lose adhesion and become detached.
Fig 94b: Providing shade for all lime stabilized work
Fig 95- Wet the walls before applying render
v) Lime Quality
Apply mixes that incorporate finely powdered quicklime immediately they have been
mixed, and mix small quantities at a time. If best quality fully reactive quicklime powder is
not available, use a greater proportion of fresh lime putty instead.
vi) Storage and protection of mixes
Generally mixes using lime should be used soon after mixing but during the course of the
work, store prepared lime putty based mixes in the shade and cover with damp cloths or
sheeting to keep them from drying out (fig 96).
Mixtures that incorporate quicklime should not be stored and should be used immediately
following mixing, once all the quicklime has fully slaked. Use all mixes before they dry out
and harden.
3.10.2 Render Application
i) Method: In a cool part of the day, apply a layer of 20mm to 30mm (3/4” average)
thick render onto dust free and dampened walls (fig 97). The optimum thickness will
depend on the render materials available, the quality of the background and the
number of render coats. Prepare a trial area before starting the main work. Apply
with wooden or steel floats, or if not available, by gloved hand. Do not render onto
dry walls.
Fig 96: Storage and protection of mixes

ii) Closing Cracks:
If two or more coats are to be applied, a small amount of cracking in the first coat is seldom
detrimental. Squash closed any cracks in the first render coat if they appear. The tendency
of the first coat to crack can be reduced in a number of ways, these include:
a) Keeping the water content of the mix low;
b) Using fine, best quality quicklime
instead of lime putty or dry hydrate;
c) Incorporating plenty of fibres in the mix;
d) Ensuring a strong key to the background;
e) Ensuring good aftercare by shading and
damping down regularly;
f) Incorporating cow dung slurry.
Fig 97: Apply render firmly to wetted background - if by hand, use gloves
Fig 98: Closing Cracks
iii) Keying for Second & Subsequent Coats: If a second finishing coat is to be applied,
scratch key the first coat when it is leather hard and well before it hardens.
iv) Wetting: Wet walls again immediately before applying a second coat.
v) Safety Precautions: Protect eyes when plastering, particularly above head height.
Keep eye wash and clean water ready for use for flushing eyes.
vi) Curing:
Shade and cure all render from hot sun for 28 days. Prepare the shade in advance
and hang it down the front of the walls, but keep it clear of the surface so the curtain
does not damage the work. Cure by wetting the walls as regularly as possible
throughout the first 2 weeks, by spraying or flicking water with a wetted brush, then
for the final 2 weeks, wet the walls a minimum of 3 to 4 times a day. Keep the shading
curtain damp and keep a bucket of water under the curtain to be readily available for
regular damping, and to help keep the air humid near the wall (fig 99). The more the
wall is wetted in a hot climate, the quicker it is likely to carbonate, and the more
effective its flood resilience.
If one or two large sheets for shading could be prepared and fixed to two long sticks, these
could be leant against the wall and moved in line with the movement of the sun. Better is
to protect all walls fully for 28 days
Fig 99: Cure for 28 days - keep shaded and dampened

3.10.3 Render Trial Mixes and Additional Durability
i) Additional Durabiity
ii) Test Mixes for Lime Stabilized Clay Content Earth Renders
Prepare both trial render panels and disc samples of render trial mixes, and test.
Select only fully stabilized mixes from successful disc soak testing (2.8.1) and where
the same mix performs well in terms of strong adhesion to the background,
minimum cracking and robustness of finish (3.8).
As outlined above in lime stabilized plaster mixes, incorporating best quality, fine
quicklime powder in the mix is the most effective way to stabilize clay soils for
renders and plasters, although good quality lime putty is an excellent alternative
and its stickiness assists workability of the mix. Preferably do not use dry hydrate for
renders or plasters as slightly over burnt particles may be subject to late hydration
and may continue slaking on a microscopic level in the mix and‘blow’, leaving holes
in the work (‘pitting and popping’).
iii) Fibre Reinforcement
Generally, fibres should be included in render mixes to improve binding qualities,
tensile strength and to prevent or reduce cracking. Suitable organic fibres include
straw, jute, hemp and hair. It is advisable to add chopped fibres (approx 25mm to
50mm long (1” - 2”) to all mixes. However, straw and readily bio-degradable fibres
should not be used for work below the flood line if an alternative inert fibre is
available. Fibres are particularly important additives if the lime stabilizer is in the
form of putty or dry-hydrate and not powdered quicklime. If best quality powdered
quicklime is used, this may be sufficient to eliminate shrinkage or cracking and
reduce the need for fibres.
Good curing will assist in strengthening the render against monsoon rain and
flood damage
Fig 100: Reinforcing Joins to Reduce Risk of Cracking (Cracks in flood risk zones offer
channels for water into the structure of the building and must be avoided).
Either ensure sufficient fibres are in the mix or float
wetted, damp hessian sacking or other fibrous
material (preferably not plastic) flat into the render
at junctions of structural elements and at 45
degree angles above the top corners of window
and door openings (which will reduce the risk of
cracking at these vulnerable points (fig 100).
iv) Render Reinforcement at Joins,
Corners or Junctions:
Consider variations to trial mixes if additional durability is required. These could
include additional short chopped fibre or hair; well graded sharp sand; coarse sand
and fine gravel, stone or marble dust or grit and slurried cow dung with only enough
water to make the mix plastic and workable. Not too wet. Mixes without increasing
the proportion of these ingredients may also be satisfactory. See Section 3.8 for
Render Panel Testing.
v) Trial Render with Clay Rich Soil
A typical mix to test for lime stabilized render could be 2 lime putty to between 10 to
20 parts clay soil plus 1 part of cow dung slurry and 3 to 5 or more parts fibre (hair or
short chopped straw). The lime/soil proportions to be determined by testing as set
out in Stage 3 testing. Mix very thoroughly. Use a shovel to turn the mix over.
Achieve a consistent colour of mix. If lime putty is used as an alternative to quicklime
a greater volume will be required and there may be less effective stabilization.
For render, fine quicklime powder can be incorporated in the mix immediately
before it is used and before the mix sets, which could be between 15 minutes and ½
hour. Take care. Wear personal protection. If the production of good quality fine
quicklime powder is not practical, use a larger volume of good quality lime putty
instead.
vi) Trial Render with Lime Putty, Pozzolan and Sand
In addition to trial mixes for clay rich soils described above, trial mixes with lime,
sand and pozzolan only, may be appropriate if clay soils are not available. For
proportioning render, a trial mix of 2-4 lime putty: 6 brick dust, and if the subsoil has
a low clay content (less than 10%) and a high sand content: 12-18 of sandy soil which
is preferably sharp and well graded (fig 101).
Fig 101: Trial render mixes with Lime Putty, Sand and Pozzolan (subject to testing).
Try adding cow dung and fibre
? ? ? ? ?

Include an alternative trial mix of a ½ to 1 part of slurried cow dung and 2 or more
parts of short chopped fibres. Make sure the same size containers are used to
measure all parts equally. Only use enough water to make the mix sufficiently plastic
for plastering workability. Test and adjust proportions as necessary to ensure they
pass the submersion (soak) test before use.
3.11 Lime Stabilized Floor Screeds
3.11.1 Floor Finishes
Refer to the trial mixes proposed for more durable finishes and floor screeds below in 3.11.3
for a description of the way to increase the durability of screeds. In addition, consider hard
wearing materials that could be used for floor surface finishes like inserting small flat stones,
bricks and tiles. These could be whole or broken pieces set in a surface screed to form a
mosaic.They could be incorporated either in or on a floor screed using strong hydraulic lime
or lime and pozzolan mixes for the bedding and pointing mortar. Fine joints in paving
finishes of stone, brick or tile can be grouted with a strong natural hydraulic lime or lime and
pozzolan grout.
3.11.2 Screeds and Pit Linings
In order to resist water or contain it, screeds or renders will need to be impermeable or
made of a mix that could be described as very hydraulic. These may be required where
render and screeds are used for lining tanks or pits to hold water, or for floor screeds or wet
areas in a house. Mixes that are likely to achieve this will need to include high proportions
of pozzolan or clay as well as lime, or use hydraulic lime.Typically mixes such as 1 lime:3 very
fine pozzolan with 1 or 2 parts of sharp sand, or the use of eminently hydraulic lime and
sharp sand may be required.
Fig 102: Floor screeds: Trowel floor surfaces flat
and level, compress well, and possibly oil the
surface for additional weatherproofing
3.11.3 Some Suggested Trial Mixes for screeds and pit linings
Some initial trial mixes are suggested below but due to the variable nature of the materials,
they must be fully tested and confirmed as satisfactory before use in the main work.
Additional protection against water damage may be considered, for example, the inclusion
of a small amount (2% to 3%) of such as linseed or other oil or slurried cow dung or tallow
in the surface finish.
Additional wearing qualities may be possible by including marble dust or grit, or crushed
limestone aggregate or other hard ground materials in the mix. Alternatively these could be
used as a substitute for sand. Suggested trial mixes for testing, subject to materials available
(including fibres which would be short and omitted from the finishing coat) could be:
a) 1 hydraulic lime : 2 sand and/or grit;
b) 1 lime putty : 3 pozzolan :1 sharp (Hill) sand;
c) 1 quicklime powder : 2 pozzolan : 2 sand;
d) 1 quicklime powder : 3 pozzolan (ground, finely sieved brick dust);
e) 1 quicklime powder : 10 clay rich soil : 2 sand and/or pozzolan;
f) 1 quicklime powder : 2 pozzolan : 3 crushed limestone or marble grit.
Fig 103: Floor screed mixes will need a strong hydraulic set and will typically
require high proportions of pozzolan, as well as hard wearing materials
for durability

To any of the above, the addition or substitution of sand with powdered and sieved marble
dust and/or grit, or crushed limestone or other hard, inert material may achieve a harder
wearing finish. Field testing samples that have been well prepared and well cured is the best
way to make a comparative evaluation of the different mixes.
3.11.4 Protection and Aftercare
i) Protection
Keep the mix covered and protected from hot sun and from rain (fig 104). Use
hydraulic lime immediately after the lime has slaked or been mixed for best results
and strength.
ii) Keep Humid
Keep the shading curtain damp, keep a bucket of water under the curtain to be
readily available for regular damping and to help keep the air humid near the wall or
floor surface.
iii) Moisten
Moisten the screed several times a day, lightly spray or flick the finish with water.
Keep the sacking protection or other cover moist to perpetuate the rate of
evaporation from the new work.
iv) Aftercare and Curing of Screeds
Keep lightly dampened for a minimum of 1 week but preferably 4 weeks following
application – gently mist with a sprayer, or flick with water to moisten the walls
about 3 times a day, or more frequently if possible, particularly in hot weather. This
will help to strengthen the screed against wear and permeability.
Fig 104: Curing of Floor Screeds: Keep shaded and lightly
dampened for a minimum of 1 week, preferably 4 weeks
v) Testing
Mixes will vary depending on the subsoil type, so it is important to test all the
materials and mixes by making trial test samples and testing them after at least one
month’s curing, to ensure the proposed mix is satisfactory.
3.12 Finishes: Lime Stabilized Decoration and Limewash
3.12.1 Decoration
Various forms of relief or raised decoration proud of the render face may be applied on the
walls, using the same finishing render coat mix, possibly with an additional proportion of
lime or fine sharp sand, or possibly marble dust added for strengthening the delicate
decoration against abrasion and rainwater. Scratch and wet up the wall before applying
additional material to ensure a good bond (fig 105). The name given to this type of
traditional decoration in England is pargeting.
Fig 105: Raised Decoration:
Scratch key the render and moisten
before applying raised decoration
Fig 106: Brush down the walls to remove
dust and debris, prior to wetting the walls
and applying lime wash

3.12.2 Limewash as a Paint
Following the curing of plaster or render and before removing the shading material, either
decorate with pargetting (rasied decoration - see above), or finish the surface with three or
more coats of limewash which will further protect the walls and the plaster from water, and
will help seal any small cracks. A pure lime or slightly hydraulic lime as the principal binder
may be used for limewash.
3.12.3 Limewash Preparation, Application and Aftercare
When limewashing, it is important to protect the eyes. Wear goggles.
i) Wall Preparation for Limewash
For good adherence of the limewash, first brush down the walls to remove any dust
and debris (fig 106). Thoroughly damp down the face of the wall about half an hour
before application, then again a few minutes before application.This will ensure that
the thin coat of lime wash bonds well, and does not dry out too quickly. (The lime
wash will need the same damp and slow drying conditions for carbonation as all
lime stabilized elements. Fig 107). Ensure however, that the walls are not running
with surface water before applying the limewash.
ii) Mixing External Limewash
After curing lime stabilized plasters and renders, prepare a coat of limewash. Keep
the shading material on the walls ready to shade the lime wash coats.
The lime wash may be of either pure putty lime and water or slightly hydraulic lime,
or a mix of 1 part lime putty with fine pozzolan (approximately 1 up to 3 pozzolan to
6 fresh putty) depending on pozzolan reactivity test results.
Fig 107: Wet the walls thoroughly half an hour so before applying lime wash: then
again 5 minutes beforehand and leave to soak in, to ensure the porous background
renders or plasters will not dry out the thin lime wash coats too quickly
Add sufficient water to bring it to the consistency of thin milk, mix it thoroughly and
pass it through a fine sieve. Ensure that it is well stirred during application to keep
the lime particles in suspension all the time. Add natural earth pigments to the
limewash for any colouring required. Generally it is recommended to keep the
quantity of pigment below 6% of the lime putty to minimize any reduction in the
performance of the final limewash (figs 108 and 111).
iii) Limewash Application
Apply thin coats by brushing vigorously with a stiff natural bristle brush, onto
already wetted walls with a hard scrubbing action (Fig 109). Apply at a cool time of
day and dampen down again several times after it has dried, which will help it to
carbonate. The speed and extent of carbonation will be increased the more
frequently this process is repeated. Keep the walls protected from sunshine by
shading at all times of day until the final coat has cured.
Fig 108: Making Limewash -
Add enough water to best quality lime
putty to bring it to the consistency of
THIN goats milk to make lime wash
Fig 109: Apply lime wash
to wetted, shaded walls
- not in direct sunlight

After 24 hours, apply a second coat of limewash onto wetted walls. Repeat the
process for a suggested minimum of 5 coats, each applied no sooner than 24 hours
before the application of the earlier coat. The last one or two coats of lime wash can
have a small amount of earth pigment added as colouring if required.
iv) Second and subsequent Coats
Fig 110: Applying next coat
of limewash: leave 24 hours
before applying subsequent
coats of limewash
Fig 111: Add small amounts of earth
pigments for colouring limewash.
Mix well. (Mix enough quantity to cover
an entire wall for colour match)
v) Durability
For best results limewash should be very thin when applied. It is better to apply as
many as 5 coats that are thin rather than one or two thick coats, which are more
likely to crack, and to peel off the wall. Limewash which is slightly less than the
density of milk is recommended. Thin goats milk is a useful comparison.
Additional water shedding properties can be achieved by adding a small proportion
(say 3%) oil, such as coconut, linseed oil or a similar oil, to the last finishing coat of
limewash. (Note: If an oil additive is applied sooner than the last coat, it will reduce
the adhesion of a further coat of lime wash).
vi) Limewash Aftercare
After completion of each coat of limewash application, keep it fully shaded from the
sun and protected from rain. Lightly damp the surface down several times a day
after it has dried. Continue this process for a week or more for best results (figs 112a
and 112b).
Fig 112a: Keep each coat of limewash fully
shaded and cured for a minimum of 24 hours
before applying the next coat

3.13 Roof Finishes
The formation of roof finishes may be considered in a similar way to floor finishes and
screeds, particularly for flat or mono pitch roofs. (Although flat roofs are not always
appropriate for buildings of natural materials - it is far more sensible to design roofs to shed
water as quickly as possible). For traditional and vernacular low pitched roofs however, the
structure supporting the roof must be sufficiently robust and firm to ensure there is no
flexing or movement to the screed and finish due to self weight which will be substantial.
This is important to avoid the finish cracking and subsequent water ingress. A degree of
flexibility in a roof screed is desirable to minimise the chance of cracking, so trial mixes with
the addition of fibre or cow dung are recommended.
Fig 112b: Fully cure all lime stabilized work
- keep shaded and dampened for only 28 days
Ensure all lime stabilized roof finishes are well shaded and cured for 28 days.
For pitched roofs, precast or fired clay tiles are a more durable finish than screed on matting
or earth, often used for low pitch sloping roofs on houses in the tropics.
Provided good thatchers are available, an excellent solution to low cost and effective
roofing is well laid thick thatch to a steep pitch. This can often be more comfortable and
cooler for the occupants than a flat or low pitch roof as it has greater insulating properties
than most other readily available roofing materials.
Fig 113: Good thatch, laid to a good depth at a good pitch, can be an excellent roofing
option in terms of weather resistance, thermal efficiency, cost and zero carbon footprint.
Screeds of this nature, provided they are well detailed and tested, that include expansion/
movement joints, and there are good falls and overhangs or chutes for the discharge of
rainwater, can prevent water ingress.They may also be suitable for paving finishes to upper
terraces and platforms for refuge above flood level, particularly if tiled.

Fig 114: Durability over Generations
Care and attention to testing local low cost materials and making, curing and testing trial
mix samples with those tested materials; using the same materials and the same successful
ratio of lime to soil (and pozzolan if necessary), should all result after only 28 days of curing
in a durable building - a building that should stay stable in flood conditions for many
generations ahead.
It is clear from many trials and from experience that the lime stabilization of soil can be
successful with a wide range of mix proportions. Due to the variability of soils and clays
however, it is essential to follow the test procedures in stage 1, 2 and 3 as recommended in
this Manual for consistent and reliable results.
We wish you good luck in following and implementing the simple steps laid out in the
manual, for the construction of durable, stable, low cost and low impact building material.
This manual was compiled for IOM with acknowledgements and thanks to Practical Action
Publishing (www.practicalactionpublishing.org) for the extensive references to Building with Earth
and Building with Lime to HANDS and IOM for their constant support and assistance throughout
Illustrations by: Juliet Breese
Deaft Design
Email: juliet@deaftdesign.co.uk
Stafford Holmes, Consultant to
Rodney Melville and Partners
10 Euston Place
Leamington Spa
Warwickshire
CV32 4LJ
Director of the
Building Limes Development Group
Tel: 07836 506 655
Email: stafford.holmes@rmpuk.com
Bee Rowan, Director
Strawbuild
Sedum Cottage
Owen Street
Pennar
Pembroke Dock
SA72 5SL
Tel: 07736 904 186
Email: beerowan@gmail.com

Establishing Quicklime Proportions
These proportions will vary dependent upon soil type but are a guide for evaluating initial trial
mixes.All percentages given are to the total amount of soil in the mix. The principal consistency of
one country to another but for practical purposes in this manual they are as set out below.
Particle Sizes:
Gravel 75mm to 5mm
Sand 5mm to 0.06mm
Silt 0.06mm to 0.002mm
burnt (none over or under burnt). In practice, compensation
for poorer burnt material may be by increasing the proportion
of it in the mix.
Lime Dry Hydrate below 0.6mm
Lime Putty 0.180mm
Mix Composition: Trial Powdered Quicklime Proportions to total Soil by Volume
Possible Shrinkage of
‘as dug soil’, in 600mm
Mould Before Lime
Addition.
Possible
Clay
Content of
Soil
Percentage
Trial
Quicklime
Addition
Percentage
Proportion
of Lime to
Soil
(Lime:Soil)
Proposed Test Mix
Proportions
Lime:Soil
(3 test specimens cubes
per mix minimum)
Shrinkage
in mm
Percentage
Shrinkage
Less than
12mm
1-2% 12-15 3-6% 1:33-1:17 1:30 1:20 1:15
12-24mm 2-4% 15-20 6-8% 1:17-1:12 1:15 1:14 1:12
24-36mm 4-6% 20-25 8-10% 1:12-1:10 1:12 1:11 1:10
36-48mm 6-8% 25-30+% 10-12% 1.10-1:8 1:10 1:9 1:8
APPENDIX 1
For details of this test method refer to Section 2.3.1.
Another starting point to establish the optimum proportions of quicklime for soil stabilization is to
1/5
th
the linear shrinkage method above.

Basic Field Testing Equipment
2.
ASTM
No.
Aperture Size Selected Material
1. 4
6
8
APPENDIX 2
12. Hollow rod 12.5mm ( ") diameter with one solid end (ie. Pipe or plastic marker pen /
whiteboard marker pent,
be between 15 and 25mm (5/8
1
. Linseed or other oil.

Basic Tools and Equipment for a village lime slaking and earth stabilization work.
1. Large water tight containers for storing material (eg. empty oil drums with lids) or storage
tanks dug into the ground.
2. Smaller containers – buckets and tagharis for soak testing.
4. A set of sieves or screens with selected aperture sizes from those set out in Appendix 4.
6. Shovels.
8. Boards, sacking or matting covers or old large sheeting material for shading the pits and
9. Timber moulds for brick and block making and sample test cubes.
10. Boards to move blocks.
11. Plastic sheets to lay blocks upon; plastic sheets to cover blocks whilst curing.
12. Lump hammer.
16. Vinegar/lemon.
Linseed or other oil (or barrier cream).
17. Clean water for washing off lime.
19. Brushes for limewash and cleaning tools.
Fig 116: Agricultural back-pack sprayer: A very useful addition for misting (light spraying) of walls or
blocks during the curing period. Application is easier than by hand, and gives a more uniform coverage.
Basic Tools and Equipment
APPENDIX 3 Mechanized Equipment, Types and Sources if Available
The research, development and availability of appropriate equipment and local manufacturers is
ongoing. This equipment includes the following:
Portable small jaw crusher, hammer mill, ball mill, grinder, or roller mixer for crushing and
owder.
A chaff cutter, re or straw chopper.
Rock crusher (large jaw crusher) for large aggregate.
Roller pan mixer or other form of roller or paddle mixer for mixing all materials.
Cinva ram, equivalents and alternative ramming methods for block compaction.
Machine types and costs together with names and addresses of local machine suppliers are under
investigation.
Fig 117: Cinva Ram : A manual block making machine for compressed blocks.
The ram is a steel box with a base that moves up and down and compresses and releases the block by way
of a long handled lever. It is reported that a 2 to 3 person team can make 300 lime stabilized blocks in one
day and a team of 4 - 5 can make 500 blocks per day per machine.

Sieve sizes in the selection or grading of materials
Sieve Size (ASTM) Sieve No. Material
5 mm No. 4 Soil, gravel and course sand
3.35 mm No. 6 Powdered quicklime
2.36 mm No. 8 Lime putty for render coat for
foundations
2.0 mm No.10 Medium sand
850 micron No. 20
quicklime powder for blocks
600 micron No. 30
450 micron No. 40 Soil testing
180 micron No.80
stucco and decorative work
106 micron No. 140 Fine sand
63 micron No. 230
APPENDIX 4
What is Lime ? A Geological Explanation
Lime is produced mainly from sedimentary rock.
Sedimentary rock originated as sediments, usually derived from the weathering
and disintegration either of previously existing rocks or of debris from marine life.
Fine-grained material was produced by water or wind erosion, and it was carried,
largely by rivers, to be deposited in lake and ocean depressions, or spread over the
surface of the sea bed. Limestone consists mainly, or entirely, of material produced
by plants or animals or from calcitic material precipitated from water by bacterial
or chemical action.
The skeletons and shells of marine animals are mainly, if not entirely, calcium
carbonate.When the animals die, their shells and bones fall to the sea bed and mix
with accumulating inorganic sediment. The inorganic sediment is produced by
weathering and disintegration of material, usually from land formations.The eroded
material is washed away and discharged into seas or lakes. The further the
inorganic material is from its origin, the greater the proportion of calcareous
materials in the limestone. In many cases calcareous material can make up virtually
the entire deposit, which produces a pure limestone used in many manufacturing
processes including the production of ‘pure’ (non-hydraulic) building lime.
The sediments that make up limestone can accumulate simultaneously with those
of clay, silt and sand. Some of these impurities are the origin of the ‘active clay’
component of hydraulic limes and natural cements. One of the most favourable
conditions for a build up of sediment is near the coast of seas and lakes, often in
shallow water, and where there is little or no wave action on the coastline.The clay,
silts and sands mixed with the lime give rise to lean and hydraulic limes.
APPENDIX 5

Suitability of Soils for the Addition of Lime
Soil Shrinkage
and
Swelling
Sensitivity
to Frost
Action
Bulk
Density
(kg/m3)
Voids
Ratio
General Suitability for the
addition of Lime
Clean gravel
Well graded
Almost
none
Almost
none
2000 0.35 Suitable for lime concrete. The
addition of sand will improve
performance.
Clean gravel
Poorly
graded
Almost
none
Almost
none
1840 0.45 Suitable for lime concrete but
grading and addition of sand will
improve performance.
Silty gravel Almost
none
Slight to
medium
1760 0.50 Not suitable.
Clayey
gravel
Very slight Slight to
medium
1920 0.40 Suitable for stabilization.
Clean sand
Well graded
Almost
none
Almost
none
1920 0.40 Suitable for mortars, plasters and
render.
Clean sand
Poorly
graded
Almost
none
Almost
none
1600 0.70 Suitable for mortar but grading will
improve performance.
Silty sand Almost
none
Slight to
high
Clayey sand Slight to
medium
Slight to
high
1700 0.60 Suitable for daub and soil structures.
Suitable for weak render coats
particularly in connection with weak
backgrounds.
Low-
plasticity
clay
Medium to
high
Slight to
high
1520 0.80 Suitable for stabilized road
formation and stablized earth
render, improves with the addition
of sand.
Organic silt Medium to
high
Medium to
high
Clays with
low
plasticity
Medium to
high
Medium to
high
1440 0.90 Suitable for stabilization.
APPENDIX 6
Highly
plastic clay
High Very slight 1440 0.90 Suitable for road stabilization and, if
sand is added, for soil structures.
Highly
plastic silt
High Medium to
high
Highly
plastic
organic
earth
High Very high 1600 0.70 Not suitable.
Peat Very high Slight 1600 0.70 Not suitable.

APPENDIX 7: LIME STABILIZED SOIL - TEST RECORD SHEET STRAWBUILD
DATE PREPARED
MATERIALS SELECTED
COMPONENT (Render,
Plaster, Mortar, Block,
Screed, Foundations)
% CLAY % SAND %SILT CHEMICAL
ANALYSIS
Silica
%
Alumina
%
Iron %
LAB :
SAND PARTICLE SIZE
ANALYSIS (Sieve test)
% retained on
5mm
% retained on
2mm
% retained on
0.2mm
PASSING SIEVE :
LIME TYPE QL REACTIVITY
Boil Time
PUTTY
DENSITY
HYDRATE
FINENESS
% passing
SOURCE &
SUPPLIER
LIME QUALITY
TEST MIXES - RATIO LIME (No. of
Parts)
SOIL (No. of
Parts)
SAND (No of
parts)
OTHER (Parts)
TEST MIX 1 Pozzolan / Fibre/
Dung
TEST MIX 2
TEST MIX 3
DISCS FOR
PERMEABILITY TEST
AND CUBES FOR
COMPRESSIVE
STRENGTH
LABORATORY TESTS
NUMBER OF
CUBES / DISCS
DATE PREPARED DATE TESTED TEST RESULT :
PSI
MAX:
PSI
MIN :
SOIL ANALYSIS
_________________________
LINEAR SHRINKAGE BOX
SHRINKAGE IN mm :
% QUICKLIME RANGE :
FIELD TEST RESULTS PASS FAIL DATE TEST
LOCATION
STEP TEST
CURING AT 28 DAYS SHADED WETTED START DATE FINISH DATE
APPENDIX 7
SOAK TEST DATE PLACED UNDER
WATER
NO OF DAYS
STABLE
NAME OF U.C AND
NAME OF DISTRICT :
NAME OF VILLAGE AND
HOUSE WHERE USED :
RECORDED BY :
RECORDS STORED AT :
PHOTOGRAPHS STORED
WHERE, UNDER WHAT
TITLE:
SAMPLES STORED AT :
NAME OF TEST MONITOR:
DATE : SIGNATURE :

149 LIME STABILIZED CONSTRUCTION LIME STABILIZED CONSTRUCTION
INFORMATION SHEET
Under development/Work in Progress
Strawbuild & HANDS, IOM, ACTED
Lime and Lime Stabilized Soil for Flood Recovery in Northern Districts - Pakistan
Comparative Compressive Strengths and Requirements
for One and Two Storey Buildings
________________________________________________________________________________________________
(Including lbs/in2 (psi) - N/mm2 conversions)
147.2 psi = 1 N/mm2
NB Soil blocks have the lowest thermal conductivity of most materials, other than lightweight insulation blocks.
London Byelaws 1972 requirements :
Minimum compressive strength at 28 days
N/mm2 lbs/in2 (psi) minimum
anticipated psi
at 2 years
Internal non-loadbearing walls 1.5 220.8 441.24
Loadbearing walls
for 1 and 2 storey buildings
2.75 404.8 607.2
Comparative Compressive Strengths N/mm2 lbs/in2 (psi) minimum
anticipated
psi at 2 years
Moderately hydraulic lime : 3 sand at 28
days
2.6 380 470
Eminently hydraulic lime : 3 sand at 28 days 6.0 880 1320
Moderately hydraulic lime : 2 crushed brick
at 2 years (Dibdin)
6.18 910 910
Unstabilized compacted soil block at 28 days
(Norton)
1.5 220.8 220.8
Lime stabilized and compacted soil block at 4.08 600 Over 600 -
possibly 900
on numerous and varied lime stabilized soil
between 6 weeks to 6 months by Northern
IOM and HANDS teams in
September & November 2014
700
(penetrometer
maximum
reading)
(?)
APPENDIX 8
Further Reading and References to the Text
1. Stafford Holmes and Michael Wingate, Building with Lime. Intermediate Technology
Publications Ltd. 2002, Rugby.
2. Norton, J., Building with Earth. Intermediate Technology Publications, London, 1986.
(New edition published 1997).
3. Ashurst and Ashurst B, Practical Building Conservation,Vol 2:Terracotta, Brick and Earth, English
Heritage Technical Handbook, Gower Technical Press,Aldershot, 1988.
4.. Shawn Kholucy, Chimney Parging, pp66-71: The Journal of Building Limes Forum, Flexpress,
Edinburgh, 2013.
5. Hugo Houben and Hubert Guillaud, Earth Construction. Intermediate Technology
Publications, London, 1989.
6. William Ellis, C., Eastwick-Field, J. and Eastwick-Field, E., Building in Cob, Pisé and Stabilized
Earth. Country Life Limited, London, revised and enlarged edition 1947.
7. John McCann, Clay and Cob Buildings. Shire Publications Ltd.,Aylesbury, 1983.
8. Paula Sunshine, Wattle and Daub. Shire Publications Ltd., Oxford, 2008.
9. Bruce Walker, Christopher McGregor in collaboration with Rebecca Little., Earth Structures
and Construction in Scotland. Historic Scotland, Edinburgh, 1996
10. Michael Wingate, Small-Scale Lime-Burning, Intermediate Technology Publications Ltd., London
1985.
11. Intermediate Technology Publications Ltd. now trade under the title of Practical Action
Publishing.
APPENDIX 9

APPENDIX 10 CHECKLIST AND APPENDIX 1
STRAWBUILD PAKISTAN Sept 2014 Contact Qazafi Memon: qazafimemon@gmail.com
IOM / HANDS/ ACTED Flood resilience Programme info@strawbuild.org
(Also refer to Appendix 1 from the Technical Reference Manual)
Prepare Prepare record sheets and start recording
Investigate 1 Investigate local materials: soil; sand; lime; pozzolan; straw; cow dung; oil; water.
(If possible, or if uncertain about soil suitability, conduct laboratory soil chemical
analysis).
2 Conduct soil field tests: clay content tests; linear shrinkage test, and particle
size (sieve) tests
3 Measure millimeter shrinkage. Record.
4 Conduct Quicklime Tests: (For quicklime not more than one week old from the
kiln): Observation Test; Weight test; 6 Second test; Reactivity Test
5 Slake the quicklime to putty immediately if it is not immediately to be used as
crushed quicklime or hydrated lime (ensure 2 x long handled hoes per slaking tank).
(Ideally, use slaking and settlement tanks - see design in Reference Manual)
6 Field Test for the specific gravity (Density) of the lime putty before using, to give
an indication of density: ( 1.45 g/ml ). Use Kg per litre on electronic scales or 30g
plunger for consistency test
7 Pozzolans: For low clay content soils or sandy soils or sand - Add two or more
parts of pozzolanic material to lime in the trial mix for a hydraulic set. (Finely
powdered burnt (low fired) brick dust or finely powdered burnt rice husk ash, or a
mixture of both) passing a No. 30 (0.6mm sieve).
Conduct simple reactivity test - mix with milk of lime and check hydraulic set
Stage 2: Test Trial Mixes for Stabilization
8 Conduct trial mixes - (See Appendix 1 Chart): select appropriate materials and
proportions for trying to establish a stabilized mix (to create a hydraulic set, which
stabilizes a mix under water):
a) Linear Shrinkage Test - take the dry mm shrinkage measurement
b) Calculate, with Appendix 1, trial sample mix proportions for:
i) clay rich soil plus lime (in order of preference for a stabilized mix, use 1:
Finely powdered quicklime 2: good density lime putty 3: Fine dry hydrate)
ii) low clay content soil, or sandy soil or sand plus lime plus pozzolan
9 - Make 3 different trial sample mixes for each test component with varying lime
proportions as given in Appendix 1
(blocks for foundations and wall blocks; discs for renders, plasters, mortars, screeds)
- Make 3 samples of the same trial mix for testing
- Make 3 cubes of the same trial mix for trial foundation and wall block mixes
10 a) Keep all trial sample mixes dampened at regular intervals for 28 days
b) Keep all trial sample mixes shaded from direct sun for 28 days & protected from
heavy rain
APPENDIX 10
Field
Testing
11 Field Test trial sample mixes after 28 days proper curing:
a) Dry strength test - Step Test for trial foundation and wall bricks and blocks
b) SOAK TEST - for ALL trial components, immediately after 28 days curing
- Soak test trial mix blocks and cubes for foundation and wall blocks;
- Soak test trial mix discs for mortars, renders, plasters and screeds;
c) Permeability test for renders and screeds
d) Wet strength field test - soil or concrete penetrometer test
All mixes remaining fully stabilized for over 6 months should be reproduced for
laboratory testing
RECORD: 12 Monitor curing conditions and accurately record all mixes, curing and test results.
Use the TEST RECORD SHEET and the VILLAGE TRIAL RECORD SHEET
Stage 3: Manufacture and Continue to Test Building Elements
Use / Build 13 Build ONLY with successfully tested mixes. Minimum 4 weeks soak test,
Test components for workability, e.g. trial render and plaster panels, mortar between
blocks, floor screed, on floor slab, lime wash
Continue to test all production run materials, mixes and components on a regular
basis throughout the construction process (soil source is tested; blocks from every
production run tested for stability and strength)
Training 14 Train villagers in the correct materials and proportions for preparing lime
stabilized mixes and hydraulic sets. Train women as well as men.
Teach health & safety. Use village level illustrations, posters & training aides.
Motivation 15 Motivate villagers in the benefits of lime use including costs comparison (60 - 70%
cheaper than burnt brick and cement), stability and durability, environmental, health
and heritage. Show photographs of important local and national historical buildings
that used lime. Demonstrate stability of lime stabilized blocks and discs under water
compared to strong-in-step-test mud blocks / compressed earth blocks (which will
dissolve quite quickly, usually within 20 minutes, compared to the stabilized mixes)
Document 16 Document process and results, supported by test record sheets; photographs, video,
and interviews with beneficiaries. Continue monitoring and documentation over time if
possible, particularly after monsoons and flood.
Stage 4: Laboratory Test
Lab Test If possible, replicate all mixes successfully soaked for 6 months for laboratory testing
in: wet and dry compressive strength and soil composition - to supplement and
corroborate field test results.
STRAWBUILD PAKISTAN Sept 2014 Contact Qazafi Memon: qazafimemon@gmail.com
IOM / HANDS/ ACTED Flood resilience Programme info@strawbuild.org

Glossary
Active Clay:
Aggregate:
Air Limes:
Alumina
Pozzolan
Autogenous Healing
Background
Bagged Lime
Binder
Bond
Breathability
Building Element
Calcareous material
Calcination
Calcite
Calcium Carbonate
Calcium Hydroxide
Calcium Oxide
Carbonation Carbonated
Caustic substance
Chunam
Clay
Clinker
Coarse Stuff
Cob
Coherent state
Core in quicklime
Cure to cure
Dead Burnt Lime
Density Vessel
Drag Hair Hook or Hoe

Eminently Hydraulic Lime
Fat Lime
Feebly Hydraulic Lime
Float to
Flocculation
Fly Ash
Fossil
Fraction
Free Lime
Grout
Hair Hook
Hand Picking
Hot Mix
Hydrated Lime Dry Hydrate
Hydrated Hydraulic Lime:
Hydration
Hydraulic Binder
Hydraulic Limes
Impervious
Jaghery Jaggery
Kankar
Key
Large Lump Lime
Larry
Laterite
Lath lathing
Lean Lime

Le Chatilier Test
Lime Concrete:
Lime Cycle:
Lime Pit
Lime Putty
Limestone
Limewash
Lump Lime
Matrix
Milk of Lime
Mineralogy
Mortar Mill
Non hydraulic Lime
Over Burnt Quicklime
P F.A
Pargeting:
Particle Size Distribution
Penetrometer Pocket Penetrometer
Permeability
pH Value
Phenolphthalein Indicator
Pigments
Pitting and Popping
Plaster
Plinth
Plumb Bob
Pointing

Pozzolan Pozzolanic Material
Precipitation:
Quicklime
Raking
Reactivity (of lime
Refraction:
Render:
Rhombohedral
Roller Pan Mill
Roughcast
Run of Kiln Quicklime
Sand
Sharp Sand
Coarse Sand
Soft Sand
Well-Graded Sand
Blended Sand
Screed:
Shuttering:

Silicates:
Sinter
Skim Coat
Slaked Lime
Slaking
Soil
Stabilization
Surkhi
Taghery
Tempered
Titration
Tenstile strength
Under Burnt Quicklime
Unsoundness
Water Burnt Lime
Well Graded
Workability

Fig 115: RECAP - The process and the two main methods of making Hydraulic
Mixe from Non-Hydraulic Lime, as in Southern Pakistan: 1) with clay rich Soil
2) with low clay, or sand or sandy soil
HYDRAULIC MIXES
(stable under water) from
NON-HYDRAULIC LIME and Active Minerals

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