Cement based solutions for early return to service

Innovative Floor Zone
Solutions: Cement based
solutions for early return to
service
http://www.master‐builders‐solutions.basf.ae/en‐mne

Content:
Concrete Failures: Causes
and Remedial Repairs
Screed Solutions for Rapid
Return to Service

Concrete failure is often far less
catastrophic than some failures
that we may have seen…

Concrete failures occur frequently
Under floor finishes and protective coatings‐ due to the
environments that the concrete is poured in.
Under attack from sulfate containing water from below
or around the structure.
Deterioration: concrete in contact with sulfate containing water and chloride
ions locally disrupt the passive film causing intense local corrosion to the
reinforcement steel e.g. seawater, swamp water, ground water or sewage
water. The formation of gypsum and ettringite formed during the external
sulfate attack may cause concrete to crack and scale, resulting in floor
finishes being affected.

Substrate shrinkage is a common form of these types of
failures, yet, during some intrusive investigations, we still find
concrete failure have transcended through screeds and floor
finishes.
Let’s look ‘under the covers’ and identify some of these issues
and then look at the remedial work required to get the area
back into service.

Causes of Reinforced Concrete Deterioration
Reinforcing Steel
Electrochemical
Corrosion
Concrete Matrix
MechanicalChemicalPhysical
Carbonation
induced corrosion
Stray Currents
Chloride induced
corrosion
Freeze / Thaw damage
Fire
Shrinkage / Cracking
Abrasion
Salt crystallization
damage
Alkali aggregate
reaction
Sulphate attack
Seawater attack
Acid / biological attack
Erosion / Cavitation
Excessive load
Vibration / Seismic
Settlement / Movement
Impact
Explosion
Thermal Movement
Ettringite formation
Source: adapted from EN 1504 part 9
In addition:
• Practical problems of workmanship
• Materials and design
Environmental Conditions

7
Surface Renovation System
Deterioration Prepare
Repair
System
Carbonated or
Chloride
contaminated
cover zone
spalling
Corroded
reinforcement
Cracks
Breakout
Surface
preparation
Bonding
agent
Rebar
preparation
Rebar
priming
Hand, spray or
poured application
of repair system

Concrete Deterioration
How does concrete protect steel ?
• A dense layer of cover concrete acts as a
barrier to the atmosphere
• The alkalinity released during hydration
sustains a stable oxide film (passive film) on
the surface
• Provided the alkalinity is maintained and no
aggressive contaminants are present, the steel
is protected from corrosion

Concrete deterioration
Why does steel reinforcement corrode?
Carbonation Induced Corrosion
• Acidic atmospheric gases, mainly CO2, neutralise the
alkalinity / passive layer
• In the presence of moisture and oxygen, the steel
corrodes
• Decreases the pH; corrosion starts normally at pH <
8.5
• Typically high volume, general corrosion
• Test method: Cores sprayed with Phenolphthalein
solution; areas with pH >9 are pink, carbonated
areas no colour change.

Carbonation Induced Corrosion
Carbonation creates the environment where the steel corrodes in the presence of moisture and oxygen
CO2 + H2O H2CO3 (Carbonic Acid) Ca(OH)2 + H2CO3 CaCO3 + 2H2O
Calcium CarbonateCalcium Hydroxide
How fast does carbonation occur?
• Dependent on porosity and permeability of the concrete cover
• Poorly cured or high w/c ratio concrete carbonates faster than well cured, low w/c concrete.

Concrete deterioration
Chloride Induced Corrosion
• Chloride ions from saline ground water, marine
environments and de‐icing salts penetrate the cover
• Chloride ions locally disrupt the passive film causing
intense local corrosion
• Chlorides actively promote the electrochemical
corrosion reactions
• Typically low volume, pitting corrosion
• Test Method – chloride content test on drilled dust
samples Example of typical localised pitting
corrosion caused by chlorides
resulting in serious loss of reinforcing
steel profile and integrity.

Visible Signs of Deterioration
• Cracking
• Leaching
• Spalling
• Scaling
• Stains
• Disintegration
• Wear
• Efflorescence
• Corrosion of reinforcing steel
• Mildew and algae

1
3
Areas and Most Vulnerable Structures
Obvious Locations:
• Sea spray and tidal splash zone (coastal)
• Contamination from acidic atmospheric conditions (CO2)
• Those exposed to extreme temperatures ranges (expansion
and contraction causing cracking of concrete)
• Structures exposed to harsh chemical environments
And areas that may not be obvious initially:
High exposure to underground salty (high chloride content) and
acidic soil conditions (can include malls, airports & other public
areas as well).

British Standards Institute (BSI) Part 9 Int’l Concrete Repair Institute (ICRI) American Concrete Institute (ACI)

EN 1504 – Introduction and General Principles
for the Repair and Protection of Concrete
Structures
• EN 1504 standardises repair activities and provides an improved framework for achieving succcessful,
durable repairs and satisfied clients
• EN 1504 deals with all aspects including:
– Definitions and repair principles
– Diagnosis and investigation
– Understanding the clients needs
– Product performance and test methods
– Material QA/QC
– Site application
Date of implementation of EN 1504: January 1, 2009

EN 1504 – Introduction and General Principles for the
Repair and Protection of Concrete Structures
Document
number
Description
EN 1504-1 Describes terms and definitions within the standard
EN 1504-2 Provides specifications for surface protection products/systems
for concrete
EN 1504-3 Provides specifications for the structural and non-structural
repair
EN 1504-4 Provides specifications for structural bonding
EN 1504-5 Provides specifications for concrete injection
EN 1504-6 Provides specifications for anchoring of reinforcing bars
EN 1504-7 Provides specifications for reinforcement corrosion protection
EN 1504-8 Describes the quality control and evaluation of conformity for
the manufacturing companies
EN 1504-9 Defines the general principles for the use of products and
systems, for the repair and protection of concrete
EN 1504-10 Provides information on site application of products and quality
control of the works

EN 1504 part 9 – General Principles
Related to Defects in Concrete: 1 to 6
Principle Principle Definition Description
1 Protection against Ingress Reducing or preventing the ingress of aggressive agents,
e.g. water, other liquids, vapour, gas, chemicals and
biological agents
2 Moisture Control Adjusting and maintaining the moisture content in the
concrete within specified range of values
3 Concrete Restoration • Restoring the original concrete of an element of the
structure to the originally specified shape and function
• Restoring the concrete structure by replacing part of it
4 Structural Strengthening Increasing or restoring the structural load bearing capacity
of an element of the concrete structure
5 Physical Resistance Increasing resistance to physical or mechanical attack
6 Resistance to Chemicals Increasing resistance of the concrete surface to
deterioration by chemical attack

EN 1504 part 9 – General Principles
Related to Reinforcement Corrosion: 7 to 11
Principle Principle Definition Description
7 Preserving or Restoring
Passivity
Creating chemical conditions in which the surface of
the reinforcement is maintained in or is returned to a
passive condition
8 Increasing Resistivity Increasing the electrical resistivity of the concrete
9 Cathodic Control Creating conditions in which potentially cathodic
areas of reinforcement are unable to drive an anodic
reaction
10 Cathodic Protection Applying electrical potential
11 Control of Anodic Areas Creating conditions in which potentially anodic
reactions of reinforcement are unable to take part in
the corrosion reaction

Concrete Substrate ‐ Initial Evaluation
• Main Tests
– Visual Inspections
– Carbonation Testing
– Covermeter
– Chloride Level
– Hammer Testing
• Additional Tests
– Potential Mapping
– Electrical Continuity of Reinforcement
– Concrete Resistivity
– Linear Polarization Resistance (measuring
the rate of corrosion) (i.e.Gecor 6)

Repair Mortar – Type Selection
• Essential Requirements
– Completely fill the void
– Shrinkage compensated
– No cracking
– Provide required strength (NOT excessively more)
– Prevent the formation of incipient corrosion in surrounding
concrete
– Provide equal or greater durability in service conditions to existing
concrete
– Preferably be undetectable

Surface Repair vs Structural Repair
ColumnColumn ColumnColumn
If stress level
in remaining
concrete is
acceptable
... then
surface
repair is not
required to
carry
structural
loads
(cosmetic repair)
If remaining
cross
section is
over
stressed ...
... then
surface
repairs are
required to
carry a
portion of the
structural
loads
(structural repair)

Types of Repair Mortar
Generic types of repair mortar
» Cementitious
Polymer modified possibly with nano‐fibres to control cracking
shrinkage compensated
required workability for hand, poured or spray application
» Resinous
Epoxy, Polyester or Methacrylate Resins
usually only small volume repairs, or crack reinstatement
» Polyurethane
Specialist Flexible PU mortar applications
e.g. embedment of trafficable expansion joints (cycling movement); also for non‐static
(dynamic) crack reinstatement

Surface Preparation
• Grit Blasting or Ultra High Pressure
Water Jetting ‐ large areas
– Removes Surface Laitance
– Open surface defects and
blowholes
– Create surface for repair and
coatings
• Saw Cut and Break‐out agreed
defective areas (minimum depth 3 x
diameter of aggregate)

Reinforcement Preparation
• Clean Reinforcement by:
– Grit blasting
– Sanding with Emery paper
– Wire brushing
• Prime with Zinc Rich Primer
– Preserves surface preparation of
reinforcement
– Helps prevent formation of incipient
anode in surrounding concrete

Application of Bonding Agent
• Function
– Enhance the bond between the substrate and the re‐profiling mortar
• Generic Types
– Potable water – saturated surface dry condition
– Styrene‐Butadiene‐Rubber (SBR) Latex
– Acrylic Latex, Poly‐Vinyl‐Acetate (PVA)
– Slurry of Re‐profiling Mortar
– Standard Cement Slurry
– Solvent‐free Epoxy
• Application
– By Brush onto Damp Concrete (repair mortar applied whilst wet)

• Forced Action Mixer
• Drill and Paddle
Mixing Repair Materials
Formwork for large repairs:
• Speed of installation
• Ease of installation
• Formed surface finish
• Reinstate surface features
Hand poured application:
• Micro concrete repairs
Hand applied mortar
Spray Applied (Wet)
Spray Applied (Dry)
Application Methods

Concrete Repair – Systematic Approach
• Preparation
• Breaking Out
• Reinforcement preparation
• Priming Steel and Concrete
• Application
• Curing
• Protective Coatings

Next step: the Screed
The concrete repair is complete‐
• appropriate concrete repair mortar ‐ fast track repair
• follow appropriate curing time
• prepare floor zone for new floor finish.
What is a screed? The Definitions:
BS EN 13813 defines a screed as: A layer or layers of screed material laid in situ, directly onto a base, bonded
or unbonded, or onto an intermediate layer or insulating layer, to obtain one or more of the following
purposes:
• to obtain a defined level;
• to carry the final flooring;
• to provide a wearing surface.
BS 8204‐1 defines a leveling screed as “a screed suitably finished to
obtain a defined level and to receive the final flooring”. A wearing
screed is defined as “a screed that serves as a flooring”.

The Objective

General Screed Constructions
Bonded screed:
• Primer/ mechanical key bonds the
screed to the existing base.
• The screed depth is generally:
• 10 mm to 40mm for modified cement
screeds
25 to 40mm for standard sand cement
screeds
• Important Note:
1. Any laitance should be removed by
mechanical means eg captive shot
blasting.

Un‐bonded Screed: is applied
over a Polythene membrane or
DPM (damp proof membrane)
at a depth of 40mm to 160mm

Floating screed: is screed laid on top of insulation.
BS 8204‐1 requires min. 75mm
(65mm in domestic applications)
Modified Screed Systems can withstand
temperatures ranging from – 30C to 80C.
Screeds can also be applied as light weight
screed with a combination with
Light density aggregate eg Lytag/ Perlite
The density can be varied from:
1700 kg/M3 – 30 Mpa
1500 kg/M3 – 25 MPa

•The mix should always be specified by weight!
Sand:cement 4:1
•Damp sand can ‘bulk up’ in volume by up to
25% compared with dry sand.
•Mixing by weight the maximum error is 5%.
•The specification should state that
sand:cement screed should be mixed to a
workable and compactable mix by a force action
mixer.
Correct Mixing

BS 8204: Part 1: 2003 recommends
sand conforming to BS EN 13139.
5.3.4 Sand for cement sand leveling screeds
The preferred grading (for a thin bonded screed) would be a 0/4 sand
with a fines category 1 within the range MP, and ideally have a
grading between 20% to 66% passing the 0.5 sieve. For further
discussion see Annex B.

BS 8204 provides guidance on design, material selection, workmanship and testing.
Prior to the introduction of BS EN 13813 it was the UK standard screeds were
manufactured to.
Factory produced screeds are required to conform to BS EN 13813, however screeds
produced on a building or construction site are normally manufactured in accordance with
the recommendations in BS 8204 which is far more comprehensive than BS EN 13813.

Category
Maximum depth of indentation
mm
Bonded and Unbonded
Screeds (see Annex D)
Floating screed
(see Annex E)
A
B
C
3
4
5
3
4
2.5
(using 2kg weight only)
Table 4 — Acceptance limits for in situ crushing resistance
test (after dropping the weight four times)

Testing Screed for Soundness

Class
Maximum permissible departure from the
underside of a 2m straight edge resting in
contact with the floor (see Appendix D)
SR1 3mm
SR2 5mm
SR3 10mm
Table 8, BS 8204‐1
Surface Regularity

Failures may be due to:
• Mix being too wet or dry
• Sand being too fine
• Wrong type of mixer
Common Screed Failures: Mixing

Good Preparation, Mixing and Application
= Good result

New innovative “Fast Setting, Drying
and Hardening” screeds‐ 1 to 3 days
Screeds with admixtures‐ 1 to 2
weeks
Traditional screeds – minimum of 3
weeks drying time
Concrete – minimum of 6 months
Traditional
screed
Concrete
Screed with
Admixtures
Curing Times
Fast Setting, Drying &
Hardening Screeds

Fast Track Installations
Rapid Drying Screed for Fast Track Installations
• Normal or Rapid Setting - Time taken to set. This characteristic
determines the working time on site.
• Normal or Rapid Hardening - Time taken to take loads. This
characteristic determines the rate of strength development.
• Normal or Rapid Drying - Time taken for screed to dry. This
characteristic determines when the flooring can be installed.

• Reduced time on site-
commercial and program
schedule savings
• Area is back in service quickly
for client- commercial revenue
• Reliable repair- confidence in
the rapid strengthening and
drying of the system to ensure
longevity
Fast Track Solutions: Obvious Benefits

BASF Construction Chemicals UAE LLC
ADDRESS:
Dubai Investment Park 1
PHONE:
+971 4809 0800
EMAIL:
INFO@BASF.COM

THANK YOU

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Cement based solutions for early return to service

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Cement based solutions for early return to service