IRC 120.pdf

IRC:120-2015
RECOMMENDED PRACTICE FOR RECYCLING OF
BITUMINOUS PAVEMENTS
Published by:
INDIAN ROADS CONGRESS
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Sector-6, R.K. Puram,
New Delhi-110 022
June, 2015
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IRC:120-2015
First Published : June, 2015
(All Rights Reserved. No part of this publication shall be reproduced,
translated or transmitted in any form or by any means without the
permission of the Secretary General Indian Roads Congress)

IRC:120-2015
CONTENTS
S. No. Description Page No.
Personnel of the Highways Specifications and Standards Committee i-ii
1 Introduction 1
1.1 Introduction 1
1.2 Recycling of Pavement 2
1.3 Reclaiming and Reprocessing of Pavement Materials 2
1.4 Variability in terms of Aggregate Gradation and Binder Content 2
1.5 Overview of Reclamation and Recycling 3
1.6 In-place Handling of Reclaimed Materials 3
1.7 Performance of Recycled Pavements in India 3
1.8 Different Aspects of Recycling 4
1.9 Reclamation 4
1.10 Hot In-place Recycling (HIR). 4
1.11 Hot In-plant Recycling (HIP) 5
1.12 Cold in-place Recycling (CIR) 5
1.13 Cold in-plant Recycling (CIP) 5
2 Scope 5
3 Investigations 6
3.1 Pavement Condition 6
3.2 Pavement Composition and History 6
3.3 Structural Evaluation 7
3.4 Existing Pavement Material Properties 7
4 General Criteria for Investigation to Determine Recycling Option 7
4.1 Serviceability of Pavement 7
4.2 The Extent of Surface Defects 8
4.3 Structural Strength 8
4.4 Recycling Options 8
4.5 Limitations as to Depth of Recycling 9
4.6 Limitations as to Proportion of Reclaimed Materials in the
Recycled Mixes
9
4.7 Some Illustrations on Selecting a Recycling Option 10

IRC:120-2015
5 Design Considerations 12
5.1 Managing the Variability in Properties of Reclaimed Materials to
make them Compatible with Fresh Materials
12
5.2 Method of Improvement of Binder in the Reclaimed Material 12
5.3 Rectification of Aggregate Grading 13
5.4 Mix Design Considerations 13
5.5 Mix Design Procedure using Foam Bitumen 14
6 Reclamation 14
6.1 Milling 14
6.2 Pavement Demolition 16
6.3 Full Depth Reclamation (FDR) 16
6.4 Management of Reclaimed Material Stockpile 16
7 Cold Recycling 17
7.1 Cold in Place Recycling (CIR) 17
7.2 Cold in Plant Recycling (CIP) 20
8 Hot in Plant Recycling (HIP) 20
9 Hot in Place Recycling (HIR) 21
10 Full Depth Reclamation (FDR) 22
11 The List of Projects Executed in India 25
12 Important Parameters to Ensure Success of Recycling. 25
13 List of Annexes
Annex 1 -
Guidelines for Mix Design, Construction and Quality
Control for Cold in plant and Insitu Recycling using foam
Bitumen Mixes
27
Appendix I to Annex 1 -
Mix Design Procedure for Foamed Bitumen Stabilisation
31
A1.1 Equipment Requirements 31
A1.1.1 Calibration of the bitumen flow rate 31

IRC:120-2015
A1.1.2 Checking the water flow rate 32
A1.2 Determination of the Foaming Characteristics of Bitumen 32
A1.3 Sampling and Preparation 34
A1.3.1 Field Sampling 34
A1.3.1.1 In-situ Treatment 34
A1.3.2 In-plant Treatment 34
A1.3.2.1 Sample blending 34
A1.3.3 Preparation of Samples for Mix Design Procedure 35
A1.3.3.1 Standard soil tests 35
A1.3.3.2 Representative proportioning 35
A1.3.3.3 Sample quantities 36
A1.3.3.4 Hydroscopic moisture content 36
A1.3.3.5 Active Filler Requirements 36
A1.4 Mixing the Prepared Samples with Foamed Bitumen 37
A1.5 Manufacture of 100 mm Diameter Briquette Specimens 39
A1.6 Curing the Briquette Specimens 39
A1.7 Determination of Bulk Density 40
A1.8 Strength Test Procedures 40
A1.8.1 Determination of Indirect Tensile Strength (ITS) 40
A1.9 Interpretation of Test Results 41
Appendix II to Annex 1
Quality Assurance Testing For Foamed Bitumen Stabilised Layers
44
A2.1 Scope 44
A2.2 Daily Production Record 44
A2.2.1 In-situ Treatment 44
A2.2.2 In-plant Treatment 44
A2.3 Quality Requirements 45
A2.3.1 Foaming characteristics 45
A2.3.2 Depth of Recycling/Thickness of the Compacted
Layer
46
A2.3.3 Compaction of the Completed Layer 46
A2.3.4 Strength Characteristics from Field Samples 46
A2.3.4.1 Determination of the Moisture / Density Relationship 46
A2.3.4.2 Manufacturing Briquette Specimens 46
A2.3.4.3 Curing the Briquette Specimens 47
A2.3.4.4 Determination of Bulk Density 47

IRC:120-2015
A2.3.4.5 Determination of the Indirect Tensile Strength (ITS) 47
A2.3.5 Strength Characteristics from Core Specimens 47
A2.3.5.1 Extracting Core Samples 47
A2.3.5.2 Cutting Core Specimens 47
A2.3.5.3 Curing the Core Specimens 47
A2.3.5.4 Determination of Bulk Density 48
A2.3.5.5 Determination of the Indirect Tensile Strength (ITS) 48
Appendix 3 to Annex 1
Managing the Reclaimed Bituminous Materials (RBM)
49
A3.1 Managing the reclaiming process 49
A3.2 Plant Waste 49
A3.3 Contamination 49
A3.4 Processing and Crushing RBM 49
A3.5 Processing Milling Material. 50
A3.6 Millings: Recommended Processing Options 51
A3.7 Processing RBM from Multiple Sources 52
A3.8 Screening RBM during Processing 52
A3.9 Crusher Types 52
A3.10 Weather 53
A3.11 Fractionating 53
A3.12 Moving the Processed RBM Stockpiles 53
A3.13 Stockpiling to Minimize Segregation 53
A3.14 Stockpiling to Minimize Moisture 54
A3.15 In-line RBM Crushers or Crusher Circuits 54
A3.16 Advantages and Disadvantages of Different RBM
Processing
55
A3.17 Sampling and Testing the RBM 56
A3.18 RBM Variability 56
A3.19 Sampling Method 56
A3.20 Test Methods 57
A3.21 Methods for Determining RBM Bitumen Contents
and Recovering Aggregates
58
A3.22 Ignition method 58
Annex 2:
List of some Projects on Recycling carried Out in India
61
References 62

IRC:120-2015
i
PERSONNEL OF THE HIGHWAYS SPECIFICATIONS
AND STANDARDS COMMITTEE
(As on 12th
January, 2015)
1. Das, S.N. Director General (Road Development)
(Convenor) Special Secretary to Govt. of India, Ministry of
Road Transport Highways, New Delhi.
2. Addl. Director General, Ministry of Road
(Co-Convenor) Transport Highways, New Delhi.
3. Prasad, Vishnu Shankar Chief Engineer (R) S,RT, Ministry of Road
(Member-Secretary) Transport Highways, New Delhi.

Members
4. Basu, S.B. Chief Engineer (Retd.), MORTH, New Delhi
5. Bongirwar, P.L. Advisor, L T, Mumbai
6. Bose, Dr. Sunil Head, FPC Divn. CRRI (Retd.), Faridabad
7. Duhsaka, Vanlal Chief Engineer, PWD (Highways), Aizwal (Mizoram)
8. Gangopadhyay, Dr. S. Director, Central Road Research Institute, New Delhi
9. Gupta, D.P. DG (RD) AS (Retd.), MORTH, New Delhi
10. Jain, R.K. Chief Engineer (Retd.), Haryana PWD, Sonipat
11. Jain, N.S. Chief Engineer (Retd.), MORTH, New Delhi
12. Jain, Dr. S.S. Professor Coordinator, Centre of Transportation Engg.,
Dept. of Civil Engg., IIT Roorkee, Roorkee
13. Kadiyali, Dr. L.R. Chief Executive, L.R. Kadiyali Associates, New Delhi
14. Kumar, Ashok Chief Engineer (Retd.), MORTH, New Delhi
15. Kurian, Jose Chief Engineer, DTTDC Ltd., New Delhi
16. Kumar, Mahesh Engineer-in-Chief, Haryana PWD, Chandigarh
17. Kumar, Satander Ex-Scientist, CRRI, New Delhi
18. Lal, Chaman Director (Project-III), NRRDA (Ministry of Rural
Development), New Delhi
19. Manchanda, R.K. Consultant, Intercontinental Consultants and Technocrats
Pvt. Ltd., New Delhi
20. Marwah, S.K. Addl. Director General, (Retd.), MORTH, New Delhi
21. Pandey, R.K. Chief Engineer (Planning), MORTH, New Delhi

IRC:120-2015
ii
22. Pateriya, Dr. I.K. Director(Tech.),NRRDA,(MinistryofRuralDevelopment),
New Delhi
23. Pradhan, B.C. Chief Engineer (NH), PWD, Bhubaneswar
24. Prasad, D.N. Chief Engineer (NH), RCD, Patna
25. Rao, P.J. Consulting Engineer, Faridabad
26. Raju, Dr. G.V.S. Engineer-in-Chief (RB), Rural Roads, Director Research
and Consultancy, Hyderabad
27. Representative of BRO (Shri B.B. Lal), ADGBR, HQ DGBR, New Delhi
28. Sarkar, Dr. P.K. Professor, Deptt. of Transport Planning, School of
Planning Architecture, New Delhi
29. Sharma, Arun Kumar CEO (Highways), GMR Highways Limited, Bangalore
30. Sharma, M.P. Member (Technical), NHAI, New Delhi
31. Sharma, S.C. DG (RD) AS (Retd.), MORTH, New Delhi
32. Sinha, A.V. DG (RD) SS (Retd.), MORTH, New Delhi
33. Singh, B.N. Member (Projects), NHAI, New Delhi
34. Singh, Nirmal Jit DG (RD) SS (Retd.), MORTH, New Delhi
35. Vasava, S.B. Chief Engineer Addl. Secretary (Panchayat) Roads
Building Dept., Gandhinagar
36. Yadav, Dr. V.K. Addl. Director General (Retd.), DGBR, New Delhi
37. The Chief Engineer
(Mech.)
(Shri Kaushik Basu), MORTH, New Delhi
Corresponding Members
1. Bhattacharya, C.C. DG (RD) AS (Retd.), MORTH, New Delhi
2. Das, Dr. Animesh Professor, IIT, Kanpur
3. Justo, Dr. C.E.G. Emeritus Fellow, 334, 14th
Main, 25th
Cross, Banashankari
2nd
Stage, Bangalore
4. Momin, S.S. Former Secretary, PWD Maharashtra, Mumbai
5. Pandey, Dr. B.B. Advisor, IIT Kharagpur, Kharagpur
Ex-Officio Members
1. President,
Indian Roads Congress
(Bhowmik, Sunil), Engineer-in-Chief,
PWD (RB), Govt. of Tripura
2. Honorary Treasurer,
(Das, S.N.), Director General
(Road Development), Special Secretary to Govt. of
India, Ministry of Road Transport Highways
3. Secretary General,
(Nahar, Sajjan Singh)

IRC:120-2015
1
RECOMMENDED PRACTICE FOR RECYCLING OF
BITUMINOUS PAVEMENTS
1 INTRODUCTION
1.1 TheFlexiblePavementCommittee(H-2)ofIRCfelttheneedtoformulatethedocument
on Recycling of Bituminous Pavements. The draft “Recommended Practice for Recycling of
Bituminous Pavements” prepared by Dr. Sunil Bose was discussed in a series of meetings
of H-2. Committee.The H-2 Committee finalized the draft document in its meetings held on
3rd
January, 2015 for placing it before the Highways Specifications Standards Committee
(HSS). The HSS approved the draft document in its meeting held on 12th
January, 2015. The
Council of IRC in its 204th
meeting held at Bhubaneshwar on 19th
January, 2015 approved the
draft “Recommended Practice for Recycling of Bituminous Pavements” after taking on board
the comments offered by the members.
The Composition of H-2 Committee is as given below:
Sinha, A.V. -------- Convenor
Bose, Dr. Sunil -------- Co-Convenor
Nirmal, S.K. -------- Member Secretary
Members
Basu,Chandan Mullick, Dr. Rajeev
Basu, S.B. Pachauri, D.K.
Bhanwala, Col. R.S. Pandey, Dr. B.B.
Bongirwar, P.L. Pandey, R.K.
Das, Dr. Animesh Reddy, Dr. K. Sudhakar
Duhsaka, Vanlal Sharma, Arun Kumar
Jain, Dr. P.K. Sharma, S.C.
Jain, Dr. S.S. Singla, B.S.
Jain, N.S. Sitaramanjaneyulu, K.
Jain, R.K. Tyagi, B.R.
Jain, Rajesh Kumar Rep. of DG (BR)
Krishna, Prabhat Rep. of IOC Ltd.
Lal, Chaman Rep. of NRRDA (Dr. I.K. Pateriya)
Corresponding Members
Bhattacharya, C.C. Kandhal, Prof. Prithvi Singh
Jha, Bidur Kant Kumar, Satander
Justo, Dr. C.E.G. Seehra, Dr. S.S.
Veeraragavan, Prof. A.

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Ex-Officio Members
President, (Bhowmik, Sunil), Engineer-in-Chief,
Indian Roads Congress PWD (RB), Govt. of Tripura
Honorary Treasurer, (Das, S.N.), Director General
Indian Roads Congress (Road Development), Ministry of
Road Transport Highways
Secretary General, Nahar, Sajjan Singh
1.2 Recycling of Pavement
Recycling of pavement is the process in which the existing pavement materials are reclaimed
and re-used after reprocessing for either (a) resurfacing, or (b) repaving, or (c) reconstruction of
pavement depending upon the condition of the existing pavement, the nature of the reclaimed
materials, the method of reprocessing, and the treatment that the pavement requires. The
justification for reclaiming the pavement materials, consisting mainly of aggregates and
bituminous binders, is both environmental as well as economic. The aggregates existing
in the pavement are part of natural resources drawn from the environment and should not
be simply dumped at dump sites if a pavement fails or becomes unserviceable because it
will cause damage to the environment, which will be further accentuated by extracting more
virgin aggregates from the environment in replacement of the wasted materials. Economic
justification comes from the utilization of the bitumen already existing in the pavement, which
reduces the requirement of expensive virgin bitumen.
1.3 Reclaiming and Reprocessing of Pavement Materials
Thereclaimingandreprocessingofpavementmaterialsinvolvebothdesign(howthepavement
should be designed using reclaimed materials with the given properties) and technology (the
methods to reclaim and reprocess, equipment, knowhow and quality) issues. Once both
the issues are satisfactorily handled, there should be evidence of good performance of the
recycled pavements in terms of strength, durability, and serviceability. If the three factors
(design, technology and performance) combine, recycling of pavements is environmentally
and economically better option for pavement repair, rehabilitation or reconstruction compared
to one which uses fresh or virgin materials.
1.4 Variability in terms of Aggregate Gradation and Binder Content
The reclaimed materials usually have lot of variability in terms of aggregate gradation
and binder content depending upon the location they come from (i.e. the project site and/
or stockpiles), the layers they are drawn from (surfacing, bituminous base, or the granular
bases), the method used for reclaiming (milling, ripping, breaking). This variability, which is
required to be accounted for in designing a mix of uniform quality meeting the standards, is
the designer’s nightmare.

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3
1.5 Overview of Reclamation and Recycling
The complete technology package requires consideration and provision of all the processes,
viz. reclamation of the pavement materials (milling, ripping, breaking) handling the reclaimed
materials (in-place or off site), the processing of the reclaimed materials (to achieve the
design gradation including by adding fresh aggregates and to produce the new mix with the
graded aggregates including by adding fresh binder) and construction. There are essentially
two types of recycling technology, viz. (1) In-place and (2) In-plant, each having two variants,
viz., (a) Cold and (b) Hot. Cold recycling technology has three options, viz., (i) Foam bitumen,
(ii) Emulsion, (iii) Stabilization. Hot technology has two options depending upon the manner
of reclamation by (i) hot process, or (ii) cold process. This is explained in the Fig. below.
The complete technology package requires consideration and provision of all the processes, viz.
reclamation of the pavement materials (milling, ripping, breaking) handling the reclaimed
materials (in-place or off site), the processing of the reclaimed materials (to achieve the design
gradation including by adding fresh aggregates and to produce the new mix with the graded
aggregates including by adding fresh binder) and construction. There are essentially two types of
recycling technology, viz. (1) In-place and (2) In-plant, each having two variants, viz., (a) Cold
and (b) Hot. Cold recycling technology has three options, viz., (i) Foam bitumen, (iii) Emulsion,
(iii) Stabilization. Hot technology has two options depending upon the manner of reclamation by
(i) hot process, or (ii) cold process. This is explained in the Figure below.
Figure 1: Overview of Reclamation and Recycling
1.5 In-place handling of reclaimed materials
The in-place handling of reclaimed materials is usually combined with mixing, laying and
construction each in a close sequence. Off-site handling involves independent processes, such as re-
crushing, segregation into different size fractions and stockpiling. Mixing (with or without heating
and/or addition of fresh or virgin materials) is a separate off-site process, which is to be followed by
transportation, laying and construction.
1.6Performance of Recycled Pavements in India
As for performance of recycled pavements in India, the evidence is only anecdotal and no
systematic documentation is available though it has been sporadically used in several projects in the
Recycling
Reclamation
In-place In-plant
Hot process
Cold Process
Hot In-place Hot In-plant
Cold In-place Cold In-plant
Stabilization Foam Bitumen
Emulsion
Hot Mix
Fig. 1: Overview of Reclamation and Recycling
1.6 In-place Handling of Reclaimed Materials
The in-place handling of reclaimed materials is usually combined with mixing, laying and
construction each in a close sequence. Off-site handling involves independent processes,
such as re-crushing, segregation into different size fractions and stockpiling. Mixing (with
or without heating and/or addition of fresh or virgin materials) is a separate off-site process,
which is to be followed by transportation, laying and construction.
1.7 Performance of Recycled Pavements in India
As for performance of recycled pavements in India, the evidence is only anecdotal and
no systematic documentation is available though it has been sporadically used in several
projects in the country. The absence of Guidelines on the subject may be one of the reasons
for lack of its widespread use. There are many documented evidences from abroad for good
performance of the recycling technology subject to fulfilment of certain site specific and
material specific requirements.

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1.8 Different Aspects of Recycling
These Guidelines are framed to cover the following five aspects of recycling:
1. Reclamation (hot and cold processes)
2. Hot in-place recycling (HIR)
3. Cold in-place recycling (CIR)
4. Hot in-plant recycling (HIP)
5. Cold in-plant recycling (CIP)
1.9 Reclamation
Hot process reclamation is applicable only in HIR, while Cold Process reclamation can
apply to all other recycling processes. In Hot Process reclamation, the existing pavement is
heated by radiation and then milled or scarified while the hot bituminous surface is soft due
to heating. The reclaimed material is invariably used in-place. In Cold Process reclamation,
the pavement material is reclaimed by Cold Milling, breaking or ripping. In cold milling the
pavement surface is milled to the required depth, the reclaimed material is discharged into
a tipper truck and stockpiled at some designated site. The reclaimed materials are of the
same size or lower compared to what had gone into in the original construction. Where
ripping or breaking is done for reclamation, materials retrieved are in large chunks, which
have to be crushed and then stockpiled. Before stockpiling the materials could be sieved
and segregated and stockpiled into various size fractions. In any case, the dust produced by
milling process should be separated. The milled material is stockpiled at some designated
place after further crushing (if the reclamation process is by ripping or breaking the pavement
instead of milling). Other reclamation processes, which are also cold processes, may involve
ripping and pulverizing the non-bituminous bases/ sub-bases.
1.10 Hot in-place recycling (HIR).
In HIR, a train of equipment is used with capabilities to perform different functions such as
infrared heating of the pavement surface to soften it, milling the softened hot pavement
surface, transferring the milled materials into Pug mill mixer of the Recycling equipment
through a belt conveyor, adding fresh mix/binder/rejuvenator as per requirements of design
into the pug mill, discharging the remixed materials into integrated paving screeds for paving
the re-mixed output, rolling and compaction of the paved material. In HIR, 100 per cent of
the reclaimed material is utilized. However, its limitation is that no more than 50 mm thick
bituminous layer can be satisfactorily recycled (maximum 75 mm if softer binder was used in
the original construction). If the pavement needs to be overlaid from structural consideration,
a second layer of Hot mix overlay may have to be done on top of the recycled surface and
in such situations (also called repaving), HIR has to be done in two layers (or multiple
layers).

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5
1.11 Hot in-plant recycling (HIP)
This process involves production and laying of hot mix materials but not with virgin aggregates
and binder but with a combination of reclaimed stockpiled aggregates already coated with
binder and additional virgin aggregate and fresh binder to meet the requirements of the
design. Usually, some rejuvenator is used to soften the old hardened binder in the reclaimed
aggregates. Heating the reclaimed binder coated aggregates may release unacceptable
fumes while feeding them cold directly into the pug mill may reduce the mixing temperature.
The hot mix production process, therefore, has to be suitably modified. In all other respects,
hot in-plant recycling is just like normal hot mix construction. Not more than 50% of the
reclaimed material is used, though a widely accepted percentage is only 30) and the thickness
in which it can be laid is typically 100 mm.
1.12 Cold in-place recycling (CIR)
In this process, milling and mixing are simultaneous processes accomplished by a single
equipment or a train of equipment capable of milling and conveying the milled material to be
fed to a pug mill, with parallel supply line for feeding fresh aggregates also, and separate
feeding lines to the pug mill for bitumen emulsion, and rejuvenator. Where foam bitumen
is to be used, there has to be separate feeding line for hot bitumen and water to produce
the foam bitumen and then feed into the pug mill. The mixed material is discharged into the
paver hopper closely following the recycling equipment or train of equipment, then paved and
compacted. This type of recycling is considered suitable for depth upto 150 mm and the use
of reclaimed material is also of the same order (typically 30 to 50%) as in HIP.
Another variant of cold in-place recycling is Full Depth Reclamation, where the thickness
of pavement to be recycled is greater than typically 150 mm. The pavement is ripped, the
material pulverized and stabilized with lime, cement or cementitious materials and compacted
into base layer of the required strength.
1.13 Cold in-plant recycling (CIP)
The process involves production of the mix in a plant using either emulsion or foam bitumen
and laying and compaction in the usual manner. A rejuvenator is to be added in the mixing
process to soften the hard binder in the reclaimed material. The application range in terms
of depth of recycling and use of reclaimed materials is typically the same as for cold in-place
recycling.
2. Scope
The document covers the following in respect of all types of reclamation and recycling
(1) Investigations required for making informed decision on recycling
(2) Suggestions regarding appropriate methods of recycling under different
circumstances

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(3) The details of each type of reclamation and recycling (in separate Parts of this
document)
(4) Considerations in design of each type of recycling treatment
(5) The Technology and quality assurance issues involved in the process of recycling
(6) The documentation required in any recycling project.
3. Investigations
The following types of investigations on the existing pavement are required
(1) Pavement condition
(2) Pavement composition and history
(3) Structural evaluation
(4) Existing Pavement Material properties
3.1 Pavement Condition
Pavement condition will be investigated for identifying all the defects as listed out in IRC
82: 2014. In addition, cores of 150 mm diameter should be taken along the width of the
carriageway on the severely distressed section at 0.75 m, 3.85 m and 6.95 m from the inside
edge of the shoulder. Cores should be taken in a staggered manner along the length of the
pavement at locations such that one core sample every 300 m length of the road is available.
Depth of the core should be at least equal to the depth of bituminous thickness. In case the
crack is observed over the entire depth of the bituminous layer, the investigation through core
or test pits should be carried out through the granular/ bound bases of the pavement as well
to ascertain if full depth reclamation would be needed.
The cores should be referenced and photographed, and the observation recorded in terms
of crack depth, crack width and other visual observations on the core such as deficient
or uneven bitumen coating, signs of shear (diagonal or transverse cracking) or any other
observation.
The cores should be used for testing the material properties of the existing pavements.
Pavement roughness should be measured by running the Bump Integrator and stretch-wise
data should be recorded.
Skid resistance measurements should also preferably be recorded.
3.2 Pavement Composition and History
Composition of the pavement including the type of pavement layers, the layer thicknesses,
year of construction, history of interventions (resurfacing/renewal/reconstruction) and time of

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such intervention, the aggregate source (if possible), job mix formula, binder content and the
type of binder should be gathered from records and documented.
3.3 Structural Evaluation
Structural evaluation of pavement should be carried out with Falling Weight Deflectometer
in accordance with IRC 115 (2014) and the residual life of the pavement and the overlay
requirements for various time horizons (5, 10, 15 years) should be determined.
3.4 Existing Pavement Material Properties
The material of core samples should be used for determining the properties of aggregate and
binder in the existing pavement. Most relevant properties to be tested are
(i) Bulk density of the existing mix
(ii) Aggregate gradation
(iii) Binder content
(iv) Viscosity of the binder in the core samples
4. General criteria for Investigation to determine Recycling option
The results of the investigation of the existing pavements should be analysed in terms of
(i) Serviceability of the pavement
(ii) The extent of surface defects
(iii) Structural strength
4.1 Serviceability of Pavement
Serviceability of the pavement is usually a subjective assessment of the users’ needs
in terms of riding quality and comfort. One would not like to drive on a cracked, ravelled
bumpy road. To what extent the surface deterioration of pavement can be tolerated is the
decision which Road Authorities have to take within the constraints of their resources.
When the serviceability of the pavement deteriorates beyond a point, one of the options
available is recycling apart from many other maintenance and repair measures like
sealing, patching, micro-surfacing, surface renewal, etc. In order to objectively assess the
acceptable serviceability level beyond which recycling should be considered an option,
these Guidelines recommend that where (a) the distresses can be categorised as “High
Severity” distress as defined in IRC 82:2014, or (b) road roughness exceeds 3000 mm
per km, or (c) rut depth exceeds 20 mm, should be considered for recycling. All surface
renewals could be a candidate for recycling.

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4.2 The Extent of Surface Defects
It would be necessary to know whether the defects appearing on the surface are confined to
the surfacing course itself or have progressed in the lower layers of pavement as well, such
as bituminous bases or granular or bound bases/sub bases. This would be determined by
examining and analysing the cores taken during investigation. Pavement should be recycled
to the depth of distress. If the distress extends into the bituminous bases, this is a clear
indication of failure of the base as well. A strengthening overlay would be called for and
recycling combined with overlay would be a solution. If the distress extends into granular or
bound bases, the bituminous pavement material should be reclaimed and the base pulverized,
stabilized and relayed while the bituminous layers could be built using reclaimed and fresh
materials.
4.3 Structural Strength
If the structural evaluation of the pavement reveals that the residual life of the pavement is
sufficient to take the wheel load repetitions for the next five years, the pavement should be
considered as adequate for the time being and recycling of only surface layers should be
considered if the surface condition warrants it. Otherwise, recycling should be combined with
overlaying.
or (c) rut depth exceeds 20mm, should be considered for recycling. All surface renewals could be a
candidate for recycling.
4.2 The extent of surface defects
It would be necessary to know whether the defects appearing on the surface are confined to
the surfacing course itself or have progressed in the lower layers of pavement as well, such as
bituminous bases or granular or bound bases/sub bases. This would be determined by examining and
analysing the cores taken during investigation. Pavement should be recycled to the depth of distress.
If the distress extends into the bituminous bases, this is a clear indication of failure of the base as well.
A strengthening overlay would be called for and recycling combined with overlay would be a
solution. If the distress extends into granular or bound bases, the bituminous pavement material
should be reclaimed and the base pulverized, stabilized and relayed while the bituminous layers could
be built using reclaimed and fresh materials.
4.3 Structural strength
If the structural evaluation of the pavement reveals that the residual life of the pavement is
sufficient to take the wheel load repetitions for the next five years, the pavement should be considered
as adequate for the time being and recycling of only surface layers should be considered if the surface
condition warrants it. Otherwise, recycling should be combined with overlaying.
Figure 2: General Criteria for recycling overlay and Full Depth Reclamation
Serviceability Extent of defects Structural Capacity
Ok? No Recycling
Recycling
Yes
No
Severe Distress In surface
Distress upto bituminous base
Distress upto Granular base
Less than 5 years
More than 5 years
Roughness 3000 mm/km
Recycling +Overlay
Recycling + FDR
Fig. 2: General Criteria for recycling overlay and Full Depth Reclamation
The Fig. 2 explains the general criteria for recycling either alone or in combination with
overlay or full depth reclamation.
4.4 Recycling Options
The Table below suggests which of the five recycling options would be suitable in different
situations. Where depth of recycling is limited, in-place methods (both Hot and Cold) would

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be suitable because these utilize the reclaimed materials to the maximum extent. There is
not much merit in using in-plant methods in such cases as only 30 per cent of the reclaimed
materials can be used. When recycling in deeper depth is required, in-plant methods are the
only options. As far as choice between hot or cold processes, for both in-plant and in-place
methods, is concerned, the choice would depend upon economic, environmental and the
capability (of producing the mix meeting the design requirements) factors.
Defects/
Deficiencies
Preferable Recycling options
HIR HIP CIR CIP
Serviceability of
pavement and
extent of defects
High Severity defects no
structural deficiencies
Y N Y N
High severity defects extending
up to bituminous bases N Y N Y
High severity defects extending
up to granular bases
- - Y* -
Structural strength Only resurfacing Y N Y N
Resurfacing with overlay N Y N Y
HIR: Hot In-place recycling HIP: Hot In-plant recycling CIR: Cold In-place recycling CIP: Cold
In-plant recycling
*Full Depth Recycling
4.5 Limitations as to Depth of Recycling
The following are the maximum recommended depths of recycling
HIR: 50 mm
HIP: 100 mm
CIR: 75 mm
CIP: 100 mm
In case the thickness required as per design is more, the balance thickness should be made
up by hot mix materials, the recycled layer acting as levelling course.
4.6 Limitations as to Proportion of Reclaimed Materials in the Recycled Mixes
In HIR or CIR 100 per cent of the reclaimed materials can be used. In HIP and CIP not more
than 30 per cent of the reclaimed material should be used.

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4.7 Some Illustrations on Selecting a Recycling Option
Photo 1 illustrates a ravelled surface.
Ravelling must have been preceded by
cracking. If the cracks are only in the surface
layer, HIR is a suitable recycling option.
The ravelled portion should be applied with
thin coat of emulsion to restore the lost
bitumen before HIR mix and prevent dust
contamination of the HIR mix.
Photo 2 is a typical example of fatty surface
giving poor serviceability in terms of riding
quality and skid resistance. HIR should be a
suitable option
Photo 3 shows a polished aggregate surface.
This is not suitable for any type of recycling
because the polished surfaces would not
allow bitumen to stick on the aggregates.
Chip seal, surface dressing, Micro surfacing
would be a better option to increase friction.
With or without overlaying

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Photo 4 shows a corrugated surface giving
very poor serviceability. If the corrugations
are not present in the base layer (which can
be ascertained by digging test pits across the
pavement),itcouldbeduetofaultymixdesign
using softer binder and HIR or CIR could be
an option. If the top of the granular base also
shows corrugation, it would be indicative of
subgrade failure of the pavement and Full
Depth Recycling would be an appropriate
solution
Photo 5 shows rutting and slippage, which
could be due to faulty mix design and use of
softer binder. This type of surface could be
treated with HIR
Photo 6 shows longitudinal and diagonal
cracks. Longitudinal cracks may be due to
faulty construction (lack of bond at cold joints)
while the diagonal cracks are indicative of
shear failure of the mix. Subject to further
investigations proving otherwise, HIR or CIR
could be a suitable option.

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Photo 7 shows alligator cracks on the
surface. Too much dust contamination and
loss of binder, HIR would not be a suitable
solution and HIP or CIP could be a better
option provided cracks have not progressed
deeper than the surface course.
5. Design Considerations
5.1 Managing the Variability in Properties of Reclaimed Materials to make them
Compatible with Fresh Materials
The objective of design of recycled mixes is that they should meet the same requirements as
expected of mixes with virgin materials and their performance should be equal to or better
than virgin mixes. The in-situ bituminous materials, which are reclaimed for use in recycling,
have the following characteristics:
(1) The bitumen is aged, oxidized and hardened and hence the viscosity of the reclaimed
binder is much higher than the fresh binder of the same grade as used in the original
construction
(2) The aggregates get crushed during the process of reclamation, particularly when the
reclamation is by the process of cold milling, and hence their grading changes from
those of the original mix.
(3) In case the reclaimed bituminous material is stockpiled, drawing up materials from
the stock pile may have variability with regard to physical properties and aggregate
gradation and source, bitumen grading and source.
The main design consideration is to manage these variabilities and make the reclaimed and
fresh materials compatible.
5.2 Method of Improvement of Binder in the Reclaimed Material
Hardened bitumen in the reclaimed materials has to be made softer. This can be done mainly
in two ways,
(i) By adding rejuvenating agents to bring the combined viscosity of the binder
to acceptable level. Rejuvenating agents are commercially available patented
products. The manufacturers of the materials should be required to demonstrate the

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effectiveness of their application and assure against any harmful ingredients therein.
If the rejuvenating agents do not penetrate into the hardened bitumen properly, they
would lubricate the mix and would be counter-productive.
(ii) By adding softer grade bitumen to mix with the hard bitumen extracted from the
reclaimed mix to soften it to the acceptable level. Extraction of old bitumen should be
done by Abson Recovery Method (ASTM D 1856-95 A) What is the acceptable level
of softening can be decided in the following ways:
(a) By the combined Viscosity of the mixed binder: This can be done by a standard
blending chart. One such chart developed by FHWA is shown in the Fig. 3
below.
(b) By the combined Softening point: The softening points of the old and new binder
combined in various percentages are determined to arrive at the target softening
point.
Fig 3. Blending Chart (Source NCHRP Synthesis Report 421)
5.3 Rectification of Aggregate Grading
Aggregate grading of the reclaimed material has to be determined and the missing fractions
have to be added to arrive at the appropriate grading as per IRC:111 (for Hot mix application)
and IRC:SP:100 (for cold mix application).
5.4 Mix Design Considerations
All other design considerations such as Stability, Va
, VMA, VFA, etc. would be the same as
those applicable for normal bituminous mixes prescribed in the relevant guidelines, codes or
specifications.

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Photo 8. Milling in Operation
5.5 Mix Design Procedure using Foam Bitumen
In recycling where recycling agent is foam bitumen, the design procedure is given in Annex 1.
6. Reclamation
Reclamation normally involves three processes viz milling, demolition and full depth
reclamation. In situations where recycling is to be done in place (HIR, CIR), reclamation and
recycling are combined processes.
6.1 Milling
Milling is the control removal of an existing pavement to a desired depth, using specially
designed equipment having replaceable tungsten carbide cutting teeth mounted on a rotor
drum driven by the power supplied by the milling machine. It is the most common way of
reclaiming the bituminous pavement material. It is mostly used following a cold process, and
hence commonly known as cold milling, though milling is done following hot process also in
HIR. This section deals with cold milling only.
Importantaspectstobeconsideredincoldmillingarethedepthofmilling,appropriatemilling
tools to govern the size of milled material, control of dust, collection and transportation of
milled material, and stockpiling. Milling processes should be closely examined to make
sure that the milled material is not contaminated with soil, base material, paving geotextiles,

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or other debris. This is particularly important for deep mills or milling on shoulders or
widened roadways. Milled materials that become contaminated should be used only as
shoulder material and should be stockpiled separately. A recommended maximum limit
of 1% deleterious material should be used to evaluate reclaimed bituminous materials.
The milled surface should also be inspected for “scabbing,” where thin, weakly bonded
layers are left in place. If this is observed, the milling depth should be adjusted to remove
the scab layer because, if allowed to remain in place, the performance of overlay will be
poor.
The milled surface should be inspected for uniform texture. A non-uniform texture resulting
from worn or broken tips on the milling drum can cause problems with compaction of
thin overlays. It may also cause an unsafe surface for motorcycles if the milled surface
remains open to traffic. In such cases, it should be ensured that riding surface is safe
for motorcycles, by having a reasonable limit on peak to valley distance of the milled
surface.The finished milled surface should be within 6-8 mm of a true profile grade both
in transverse and longitudinal directions, when measured with a 3-m long straightedge
(Photo 9).
If the milled surface is to be the final surface of the pavement, it should have either continuous
or intermittent striations or any other pre-approved pattern which will provide an acceptable
level of skid resistance. If pavement is to be constructed over the milled surface, it shall have
a texture which will provide good bonding.
Photo 9: Good surface after milling
Milling machines transfers maximum energy on to milling drum in removing pavement
layers by impacting the pavement with milling teeth mounted on a drum rotating at about
200 rpm. The impacts break up the pavement by ripping through the mastic and aggregate
particles. Crushing of aggregate particles causes the gradation of the millings to be finer
than the gradation of the pavement layers in place. The final gradation required of the
reclaimed bituminous materials (RBM) by milling can be obtained by controlling depth of
milling cut, and speed of machine .Also Gradation bar on milling machine helps to control
the cut size.

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Photo 10. Different types of milling teeth on rotar
6.2 Pavement Demolition
RBM may also be obtained from demolition of an existing pavement using a bulldozer or
backhoe. This process is typically limited to small areas of pavement. It is slow and results in
large chunks of pavement that may be more challenging to process into a useable recycled
material. When pavement rubble is contaminated with underlying layers and soil, it is better for
this material to be crushed and used as a shoulder or base material than used in bituminous
mixture.
The limitation of backhoe loader or excavator is that there is a possibility of damage to
the layer below the bituminous layer besides the retrieved materials, being in the form of
lumps, cannot be used without re-crushing. While disposal of unusable material lumps is
environmentally damaging, making them usable by re-crushing is also fraught with some
problems as the lumps instead of breaking may tend to become stickier due to presence of
bitumen, especially in hot weather. Thus, it is not easy to get a proper grading out of such
materials even after re-crushing.
6.3 Full Depth Reclamation (FDR)
In Full depth reclamation (FDR) all the reclaimed materials of the pavement, with or without
fresh materials, is stabilized in-situ with suitable stabilizers to produce the base course of the
pavement to be overlaid by bituminous course(s). If economically feasible, it is preferable to
reclaim the bituminous layer and other granular or bound layers separately to retrieve as much
useful and high value bituminous materials as possible. In the latter situation, reclamation
and recycling would be in two stages.
6.4 Management of Reclaimed Material Stockpile
Reclaimed material should be stockpiled and managed as per the details given in Appendix
III to Annex 1.

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7.0 Cold recycling
Cold recycling involves reuse of the existing pavement materials without the application of
heat. The recycling agent in cold recycling can be emulsion, foam bitumen, rejuvenator,
and cementitious materials, either alone or in combination. Cold recycling offers three
options,viz.,Cold In-place Recycling (CIR), Cold In-Plant (CIP) and Full Depth Reclamation
(FDR).
7.1 Cold in Place Recycling (CIR)
A CIR plant or Recycler should be equipped with
(a) Cold milling equipment to mill the existing pavement,
(b) A system to carry the milled materials to vibrating screens with a separate line for
fresh aggregates
(c) A system for proportioning and weigh batching of different size fractions
(d) A Pug mill for mixing with separate material feed lines for aggregates, binder and
rejuvenators
(e) VibratingscreedsfortampingandprofilingthemixedmaterialsdischargedfromPugmill
(f) Compaction equipment for compacting the mix
(g) Appropriate arrangements for controlling dust and noise pollution
The machines should have electronic controls for inputs, processes and outputs. A single
machine can have all these features or there can be a train of equipment for performing
different functions. Schematic diagrams for the cold in-place recycling plants are presented
in Photos 11 to 14 below.
(Source: FHWA cold in place recycling)
Photo 11: Schematic arrangement for CIR with emulsion

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(Source: FHWA cold in place recycling)
Photo 12: Another Schematic arrangement for CIR with emulsion

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Photo 13. Schematic arrangement for CIR machine using foam bitumen
Photo 14 : Another schematic arrangement for CIR with Foam Bitumen

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7.2 Cold in Plant Recycling (CIP)
In the cold in-plant recycling, the RBM is transported to a mobile cold mixing plant located
in the vicinity of the job site. Measured quantities of RBM and fresh aggregates are cold
fed into a twin shaft pug mill and metred quantities of binder, either in the form of bitumen
emulsion or foam bitumen, is injected. All the ingredients are mixed and blended for a certain
duration to produce a homogeneous mix, which is transported to the work site, paved and
compacted. The requirements of CIP, therefore, involve proper control on material feed and
mixing process, including the mixing time.
Photo 14: View of a twin shaft pug mill of a cold mixing unit
Precise control on the mixing time is important because over-mixing can cause premature
breaking of emulsified bitumen; under-mixing may result in insufficient coating of aggregates.
Similarly, the rate of injection of hot bitumen and water to produce the foam bitumen should
be so regulated that the bitumen foam uniformly coats the aggregates.The CIP plant should
have all the features and controls as described in para 7.1 above. A view of the twin-shaft
pug mill is given in Photo 14.
8. Hot in plant Recycling (HIP)
Hot in-plant recycling involves the usual Hot mix production process with three main
differences, viz (i) instead of all fresh aggregates and bitumen in the usual Hot Mix production,
HIP uses RBM to the extent of 30 %, (ii) rejuvenators are required to soften the oxidized
binder in RBM, and (iii) unlike normal hot mix production process the RBM cannot be directly
heated as it would generate fumes. These factors have to be adequately managed by brining
modifications in the Hot Mix Plants, especially the material feed system, and changes in the
production process. Subject to these modification and changes, the Plant can be a Continuous
or Batch type.

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9. Hot in place recycling (HIR)
Photo 15. Schematic arrangement for an HIR plant
An HIR Plant should have the following features and controls:
(a) An infrared radiation heating system, which can heat the existing pavement surface
uniformly
(b) A scarifier to rip the existing bituminous surface to the required depth
(c) A collecting hopper to collect the scarified hot bituminous mix from the scarified
pavement
(d) Feed lines for controlled addition of additional binder and rejuvenator to the scarified
mix in the collecting hopper
(e) A conveyor system to carry the scarified mix, additional binder and rejuvenator to the
proportioning hopper
(f) A proportioning hopper for controlled discharge of the mix to a conveying system
leading to the mixing unit
(g) A feed system for controlled addition of virgin mix to be added to the old mix
(h) A conveyor system to carry the proportioned old and new mixes to the mixing unit
(i) A mixing unit to mix the old and new mixes
(j) A discharge system for discharging the mix
(k) A spreading augur to evenly spread the mix to the surface to be overlaid
(l) A paving screed with provision for tamping and vibration
(m) A compaction unit to compact the mix after paving

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In Hot In-place recycling (HIR) the existing pavement is heated and softened, and then
scarified/milled to a specified depth. The critical issues involved in HIR plants and processes
are the heating of the pavement surface, scarification, collecting and conveying the RBM
to the mixer, addition of rejuvenators and fresh mixes into the mixer, proper mixing of all
the ingredients, laying and paving of the mat and compaction. The HIR plants, therefore,
should have all these facilities in one plant or should have a train of equipment performing
different functions in a synchronized manner. Heating, material feed, mixing and laying are
the processes to be strictly controlled. For example, heating of the surface has to be uniform
and for that the number of preheating units is not as important as the length of the heating
areas/hoods on each preheater. Similarly, the rejuvenator doses have to be metered and
controlled. Where fresh mixes are added, its input quantities have to be controlled. HIR can
be a single pass or multiple pass process. In single pass operation, the scarified in-place
material is compacted and that is the end of the process. In multiple pass operation, the
compacted mix is overlaid by fresh mix. The depth of treatment varies between 20 to 50 mm
and the temperature of the mix in the range of 110-150 deg C. Schematic arrangement for an
HIR plant is given in Photo 15.
10. Full depth reclamation (FDR)
Full Depth Reclamation (FDR) is basically a cold mix recycling process in which different
types of additives such as foam bitumen, bituminous emulsions and chemical agents such
as cement, fly ash, and lime, including commercially available cementitious stabilizers are
added, mostly in-situ, and compacted to obtain an improved base. The four main steps in this
process are pulverization, introduction of additive, mixing, compaction, and application of a
surface or a wearing course. If the in-place material is not sufficient to provide the desired
depth of the treated base, new materials may be imported and included in the processing.
New aggregates can also be added to the in-place material to obtain a particular gradation
of material.
● Pulverization should produce minus 40 mm size and should conform to the
gradation as per IRC 37 for the purpose of stabilization.
● The Sand Equivalent (SE) value from the combined materials should not be less
than 30%.
● Emulsion content, in case of bitumen stabilization should be such that indirect
tensile strength in dry and wet conditions (100 mm specimen) is more than
225 KPa and 100 KPa respectively and voids in the range of 6–8%.
● Resilient modulus for all stabilized material should be in accordance with the
IRC 37.
● Stabilization should be done in-situ with suitable plants and equipment. Where it
is not possible to have these plants and equipment (for smaller jobs), WMM plant
can be used for mixing.

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This method of recycling is normally performed to a depth of 100 mm to 300 mm.The
train of equipment consists of recycling machine hooked to a water tanker and steel drum
roller with pad foot shell. The advantages of full depth reclamation are that most pavement
distresses are treated, hauling costs are minimized, significant structural improvements can
be made (especially in base), material disposal problems are eliminated, and ride quality is
improved.
Photo 16. Milling the Bitumen Crust for FDR
Photo 17

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Photo 18
Photo 19

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Photo 20.
Photo 17-20 Stabilizing the base layers after Milling for FDR
11. List of Recycling Projects in India
The lists of some of the projects executed in India is at Annex 2.
12. Important parameters to ensure success of recycling.
The success of recycling projects would depend upon appropriate choice of the recycling
option, proper design, and selection of recycling agents, capability of plants and equipment,
and logistics of operation.
i. Choice of a suitable option: Recycling option has to be selected on the basis of
strengths and weaknesses of each option. In-place option has a depth limitation
of 50 mm (HIR) and 75 mm (CIR). In plant option is suitable for larger depths and
multi- layer construction combining an overlay.
ii. Design: To arrive at a design and Job Mix Formula involves much more effort and
many more tests and trials with different combination of RBM, fresh aggregates
and recycling agents than are required in conventional design of hot or cold mixes
because the design is highly sensitive to the properties of the RBM.

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iii. Plant capabilities: The controlled addition of the JMF ingredients for preparing
the mix is extremely important and the user of this technology should look for
these capabilities in the plants and equipment proposed to be deployed on the
project. Mechanical or hydraulic controls should be insisted upon as appropriate for
components feeding the ingredients and the latter should be weighed or metered
using electronic sensors. The processing parameters like heating, mixing, mixing
time should have electronic controls, whereby these can be preset, and auto shut
off facility when the set limit is exceeded (e.g. thermostatically controlled heat
transfer with electronic heat sensors). The plants and equipment should have
capabilities to ensure synchronized operation of various components, all controlled
from a central control panel.
iv. Logistics of operation: This is another important consideration in the use of this
technology, particularly in the in-place processes where the process has to be
carried out at the site without disturbing the traffic. Each activity from production
to completion should have a logistic planning so that the production process runs
smoothly and after the mix is produced; there is arrangement for paving and
compacting the mix within appropriate time limit.
While deciding upon Recycling treatment under any project, each of these aspects need
detailed consideration. A complete technology package should be asked to be offered by the
agency undertaking the work.

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Annex 1
Guidelines for Mix Design, Construction and Quality Control for
Cold in plant and Insitu Recycling using foam Bitumen Mixes
Annex 1 deals with various aspects of Recycling using foam bitumen. Appendix I to this Annex
deals with design procedure, Appendix II with the Quality Assurance issues and Appendix III
with how the Reclaimed Bituminous materials (RBM) should be managed.
Bitumen for Foaming:
Bitumen used for foamed bitumen stabilisation shall be penetration grade bitumen complying
with Indian Standard Specification for “Paving Bitumen IS: 73”. The grade of penetration
bitumen shall be between 60 and 150. It is desirable to specify the grade in the contract. The
bitumen should be free of any anti-foaming agent and should have the following minimum
foaming characteristics (refer Appendix I):
Expansion ratio: 8-10 times
Half-life: 6 seconds
The temperature of the bitumen at the time of foaming should be between 160°C and
190°C.
Water: Water used in the cold in-situ recycling process should be potable, clean and free of
harmful matter.
Mixture Design
The mixture design procedure to be followed for foamed bitumen stabilised material is
described under Appendix I to this Annex. Separate mixture designs shall be carried out for
each different material combination that will be encountered in the construction. The results
for each mixture design shall include:
● the temperature range at which the bitumen is to be foamed;
● the amount of water to be injected into the bitumen to achieve the required foaming
characteristics;
● details for any blending with imported material requirements (material specification
and blend ratio in volumetric terms);
● the application rates for foamed bitumen and filler as a percentage (by mass) of the
material being treated;
● target strengths in terms of Indirect Tensile Strength (ITS) tests carried out on
specimens prepared for Quality Assurance testing (as described in AnnexureII).
Tests specific to foamed bitumen stabilised materials are included inAnnexure II. The following

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additional tolerances shall apply to the foamed bitumen stabilised layer:
i) Consumption of stabilising agents and filler:
Application rates specified in the relevant mixture design ± 0.2%
ii) Strength of briquette or core specimens
Indirect Tensile Strength:
ITSDRY
value 90% of the ITSDRY
value specified in
the relevant mixture design
Tensile Strength Retained:
TSR 80% of the TSR value specified in the
relevant mixture design.
iii) Density: Densities shall be measured for the full layer thickness and related to the
maximum dry density determined as per IS 2720 (Part 8) for the relevant blend of
stabilised material. The average density of a “Batch” shall be related to the thickness
of the layer and the underlying support conditions, as detailed in Table 1.
Table 1: Density Requirements (Relative to the Maximum Dry Density for the
Material Determined in Accordance with is: 2720 (Part 8))
Layer
Thickness
(mm)
Support Conditions Beneath New Compacted Layer
Weak
(Thin Granular
Structure / Poor
Subgrade)
Moderate
(Thick Granular
Structure / Average
Subgrade)
Good
(Bound Materials /
Good Subgrade)
150 98 100 102
150 to 200 97 99 102
200 to 250 96 98 100
250 to 300 95 97 100
300 93 95 98
No individual density test result shall be less than that specified minus 2%.
Opening to Traffic
All traffic shall be kept off the completed layer of foamed bitumen stabilised material until
the surface has dried out. Whilst under traffic, the surface of the completed shall be kept
continuously damp during daylight hours by frequent light watering for at least three days.
Thereafter and until the surfacing is applied, the surface shall be continuously monitored
for signs of deterioration caused by the action of traffic. Where ravelling is detected, the
surfacing shall be applied without delay, provided the moisture content of the stabilised layer
has reduced to the required level.Alternatively, a temporary seal consisting of diluted emulsion

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(as described in Section 510) shall be applied to protect the surface until the Bituminous is
paved.
Delay before Covering
Application of the surfacing (surface dressing or Bituminous) or subsequent layer shall
be delayed until the moisture content of the upper 10 cm horizon of the foamed bitumen
stabilised layer, checked in accordance with IS 2720 (Part 2), has reduced to below 50% of
the Optimum Moisture Content (OMC) determined as per IS 2720 (Part 8) for the relevant
blend of stabilised material.
Dealing with Unforeseen Circumstances
Excess moisture: Where the in-situ moisture content of the material in the recycling horizon,
checked in accordance with IS 2720 (Part 2), is in excess of the Optimum Moisture Content
(OMC) determined as per IS 2720 (Part 8), the existing pavement shall be pulverised without
any additives to a depth 5 cm above the required recycling depth (i.e. recycling thickness
minus 5 cm). The pulverised material shall be left open to the atmosphere to dry. This drying
process can be accelerated by frequently cross-blading the pulverised material with a motor
grader, or with a plough.
After drying sufficiently (to below 75% of the OMC), the shape of the original surface shall
be reinstated by grader and compacted to achieve a nominal 95% of the maximum dry
density determined as per IS 2720 (Part 8). Thereafter, the recycling/stabilisation work may
proceed.
Sub-grade instability: Where sub-grade instability is identified during the recycling process,
it shall be treated by:
● recovering the material in the pavement layers overlying the unstable material
by either milling or excavating and loading into trucks for transport to temporary
stockpile;
● excavating the unstable material to the depth directed by the Engineer and disposal;
● treating the exposed roadbed, as directed by the Engineer; and
● backfilling the excavation using material from both temporary stockpile and imported.
Backfilling shall be undertaken in 15 cm (nominal) thick layers, compacted to the
relevant density target that will be directed by the Engineer. Successive layers shall
be constructed until the level of the existing road is reached. The top two layers
(30 cm) shall be constructed with stockpiled material, a portion of which shall then be
recycled and stabilised.
Where the measures described above are deemed necessary, the Engineer will detail the
requirements for the depth of excavation, treatment of the exposed roadbed, the quality of
material to be imported as backfill and density requirements.

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Stockpiling the Treated Material: The mixed product may be transported to site and paved
immediately or placed in stockpile for later use. Where it is placed in stockpile, care shall be
taken to ensure that the following minimum requirements are met:
– the area on which the material is stockpiled shall be carefully prepared to avoid
contamination from any source;
– the maximum height of stockpiled material shall be 3 m;
– moisture loss from the material in stockpile shall be prevented, either by covering the
entire stockpile with an impervious sheet, or by spraying the surface of the stockpile
with water every two hours between sunrise and sunset;
– no vehicles, front-end loaders or other equipment shall be permitted to drive on
stockpiled material. Stockpiled material shall be maintained in as loose a state as is
practical;
– samples shall be extracted from the stockpiled material seven (7) days after being
placed in stockpile and, thereafter, every seven (7) days whilst the material remains
in stockpile. Such samples shall be tested for moisture content and indirect tensile
strength. Samples shall be taken from each 500 mm horizon below the surface of the
stockpile to a maximum depth of 2 m;
– no material shall remain in stockpile for more than thirty (30) days unless the contractor
can show by means of laboratory tests that keeping the material in stockpile for
longer periods is not detrimental to the performance expectations of the final base
course; and
– loading material from stockpile shall be undertaken by front-end loaders running on
a thin layer of sacrificial mix on the stockpile floor. Loading shall be done in such
a manner that the material is extracted from the base of a vertical face, thereby
promoting mixing as the face collapses. All due care and diligence will be required by
the contractor regarding the safety of plant and personnel during loading operations
and to ensure that the stockpile is “made safe” at the end of work each day.

IRC:120-2015
31
Appendix I to Annex 1
Mix Design Procedure for Foamed Bitumen Stabilisation
A1.1 Equipment Requirements
The mix design procedure for foamed bitumen stabilisation requires a laboratory unit capable
of producing foamed bitumen at a rate of between 50 g and 200 g per second. The method
of production shall closely simulate that of full scale production of foamed bitumen on the
recycling machine. The apparatus shall have a thermostatically controlled kettle capable of
holding a mass of 10 kg of bitumen at a constant temperature between the range of 160ºC
and 200ºC, ± 5ºC. The unit shall have an expansion chamber similar to that on the recycling
machine in which cold water is injected into hot bitumen. Water injection shall be variable
from 0 to 5% (by mass of the bitumen) with an accuracy of 0.25%. The plant shall capable
of accurately discharging a predetermined mass of foamed bitumen directly into the mixing
bowl of an electrically driven laboratory mixer with a minimum capacity of 10 kg.
A1.1.1 Calibration of the Bitumen Flow Rate
For each different bitumen type and at each selected operating temperature, the rate at
which bitumen is discharged into the expansion chamber shall be determined for pre-set
discharge times ranging from 1 second to 10 seconds in 2 second intervals. This is achieved
by discharging bitumen through the expansion chamber and into a sized bucket at each

IRC:120-2015
32
different pre-set time interval. The mass of bitumen for each time interval is determined by
weighing and a graph of discharge vs. time plotted. This graph is used later to determine the
time required to inject a specific amount of bitumen into a mix.
A1.1.2 Checking the Water Flow Rate
The water flow rate is controlled by a manometer that is pre-set at the required flow rate (in
litres/hr.). This is checked by setting the manometer at different flow rates and weighing the
water that is discharged through the expansion chamber for a fixed period of time (normally
30 seconds).
A1.2 Determination of the Foaming Characteristics of Bitumen
The foaming properties of each bitumen type are characterised by:
Expansion Ratio. A measure of the viscosity of the foamed bitumen, calculated as the ratio of
the maximum volume of the foam relative to the original volume of bitumen; and
Half Life. A measure of the stability of the foamed bitumen, calculated as the time taken in
seconds for the foam to collapse to half of its maximum volume.
The objective is to determine the temperature and percentage of water addition that is required
to produce the best foam properties (maximum expansion ratio and half-life) for particular
bitumen. This is achieved at three different bitumen temperatures as follows:
Laboratory scale foam bitumen plant
Step 1 Heat the bitumen in the kettle of the laboratory unit with the pump circulating the
bitumen through the system until the required temperature is achieved (normally

IRC:120-2015
33
starting with 160°C). Maintain the required temperature for at least 10 minutes
prior to commencing with testing.
Step 2 Set the water flow-meter to achieve the required water injection rate (normally
starting with 2% by mass of the bitumen).
Step 3 Discharge foamed bitumen into a preheated (± 75 °C) steel drum (27.5 cm in
diameter) for a calculated spray time for 500 g of bitumen. Immediately after the
foam discharge stops, start a stopwatch.
Step 4 Using a calibrated dipstick, measure the maximum height the foaming bitumen
achieves in the drum. This is recorded as the maximum volume.
Step 5 Use the stopwatch to measure the time in seconds that the foam takes to dissipate
to half of its maximum volume. This is recorded as the foamed bitumen’s half-life.
Step 6 Repeat the above procedure three times, or until similar readings are achieved.
Step 7 Repeat steps 3 to 6 for a range of at least three water injection rates. Typically,
values of 2 %, 3% and 4% by mass of bitumen are used.
Step 8 Plot a graph of the expansion ratio versus water injection rate and half-life versus
water injection rate on the same set of axes (see the example in Fig. A1.1). The
optimum water addition is chosen as an average of the two water contents required
to meet the minimum specified foaming properties.
Step 9 Repeat steps 1 to 8 at two other bitumen temperatures (normally 170 °C and
180 °C).
A: Minimum acceptable
expansion
B: Minimum acceptable half-life
C: Equidistant
Opt: Water injection required to
achieve maximum expansion
and half-life
Fig. A1.1 Determination of the Optimum Water Addition.
15 16
14 15
13 14
12 13
11 12
10 11
9 10
8 9
7 8
2 3 4
WATER INJECTION (%)
EXPANSION
RATIO
HALF
LIFE
(sec)
EXPANSION
HALF LIFE
C
A
B
C
Opt

IRC:120-2015
34
An example.
The temperature and the water injection rate selected shall be the lowest that produces foam
with properties in excess of the minimum specifications.
Notes.
1. The temperature range for bitumen (prior to foaming) shall be a minimum of 160°C to a
maximum of 200°C.
2. The maximum water injection rate shall be 5% by mass of bitumen.
3. The minimum foaming properties that are acceptable for effective stabilisation are:
Expansion ratio: 8-10 times
Half-life: 6 seconds
If these minimum properties cannot be achieved within the limits stated in Notes 1 and 2, the
bitumen shall be deemed to be unacceptable for use in foamed bitumen stabilisation.
A1.3 Sampling and Preparation
A1.3.1 Field Sampling
A1.3.1.1 In-situ Treatment: Where the depth of recycling is fixed, bulk samples (± 200 kg) of
material from the recycling horizon are to be obtained from site using a recycler operating at
normal speeds and settings. Where the depth of recycling is not known, field sampling shall
follow the procedures described below for In-plant Treatment.
A1.3.2 In-plant Treatment: Bulk samples shall be obtained during field investigations and test
pit excavations. The layers in the upper pavement (± 300 mm) shall be sampled separately.
A milling machine or recycler shall be employed for sampling layers of bound material
(Bituminous and previously bound layers). At least 150 kg of material shall be sampled from
each layer that may be included in the mix design.
A1.3.2.1 Sample blending
Where necessary, blend the materials sampled from the different layers or from different
sources to obtain a combined sample representing the material that will be stabilised. The
in-situ density of field samples from different layers must be considered when blending
materials, as illustrated in the boxed example below. Repeat the tests described in A1.2.1
above to determine the grading and plasticity index of the blended sample.
Existing upper pavement structure
To obtain a representative mix, the two materials from the above example are blended in proportion to
200 mm Gravel
60 mm Asphalt
60 mm Asphalt
Recycling depth 200 mm = +
140 mm Gravel

IRC:120-2015
35
To obtain a representative mix, the two materials from the above example are blended in
proportion to layer thickness and in-situ density as follows:
Material Per square metre (kg) Proportion Per 10kg sample (g)
Bitumen (60 mm at 2300
kg/m3
)
0.06 x 2300 = 138 138/418 = 0.33 0.33 x 10000 = 3300
Gravel (140 mm at 2000
kg/m3
)
0.14 x 2000 = 280 280/418 = 0.67 0.67 x 10000 = 6700
Total 418 1.00 10000
A1.3.3 Preparation of Samples for Mix Design Procedure
A1.3.3.1 Standard soil tests
Determine the grading (IS 2386 Part 1), plasticity index (IS 2720 (Part 5)) and moisture/density
relationship (IS 2720 (Part 8) for the sampled or blended material that is to be stabilised.
A1.3.3.2 Representative proportioning
Separate the material into the following four fractions:
Retained on the 19.0 mm sieve;
Passing the 19.0 mm sieve, retained on the 13.2 mm sieve;
Passing the 13.2 mm sieve, retained on the 4.75 mm sieve; and
Passing the 4.75 mm sieve.
Reconstitute representative samples in accordance with the grading (determined in A1.3.2.1
above) up to the portion passing the 19.0 mm sieve. Substitute the portion retained on
19.0 mm sieve with material that passes the 19.0 mm sieve, but is retained on the 13.2 mm
sieve. The example in the table below explains this procedure:
Sieve analysis Quantity of material to be added for 10 000 g sample
Sieve
Size
(mm)
Percentage
Passing from
sieve analysis
Passing 4.75 mm
Passing 13.2 mm
Retained 4.75 mm
Passing 19.0 mm
Retained 13.2 mm
19.0 90.5
(53.6/100*10000)
= 5360g
((72.3-
53.6)/100*10000)
= 1870g
((100-
72.3)/100*10000
= 2770g
13.2 72.3
4.75 53.6

IRC:120-2015
36
If there is insufficient material for substituting that retained on the 19.0 mm sieve (i.e. material
passing the 19.0 mm sieve but retained on the 13.2 mm sieve), then lightly crush the material
retained on the 19.0 mm sieve to provide more of this fraction.
A1.3.3.3 Sample quantities
The guidelines shown in the table below should be used for estimating the quantity of material
required for the respective tests:
Test Sample Quantity Required
Gradation (IS 2386 (Part1)) and Plasticity Index
(IS 2720 (Part 5))
2 kg
Moisture/density relationship (IS 2720 (Part 8)) 5 x 7 kg
Bituminous stabilisation design (100 mm diameter
Marshall briquettes)
Minimum 10 kg per stabiliser content
Moisture contents Approximately 1 kg
A1.3.3.4 Hydroscopic moisture content
Two representative air-dried samples, each approximately 1 kg, are used to determine the
hygroscopic (air dried) moisture content of the material. (Note: Larger sample size should
be used for more coarsely graded materials.) Weigh the air-dried samples, accurate to the
nearest 0.1 g, and then place them in an oven at a temperature of between 105ºC and 110ºC
until they achieve constant mass. The hygroscopic moisture content is the loss of mass
expressed as a percentage of the dry mass of the sample.
A1.3.3.5 Active Filler Requirements
Bitumen stabilisation is normally carried out in combination with a small amount of active filler
(cement or hydrated lime) to improve dispersion of the bitumen. The improved dispersion
contributes to increased soaked strengths.
Although the use of active fillers is recommended, in parts of the world, these agents are not
readily available. In such cases, the use of crusher dust (minus 6 mm crusher tailings) or
similar material can be used.
For good quality materials, with retained strengths in excess of 80%, additional tests without
active filler should be carried out during the mix design process. The results of these tests will
allow a decision to be made as the whether the addition of an active filler is warranted.
The following application rates (by mass) of hydrated lime or cement should be used as a
guide.
Plasticity Index 10 Plasticity Index 10 – 16 Plasticity Index 16
Add 1% ordinary Portland
cement
Add 1% hydrated lime Pre-treat with 2% hydrated
lime

IRC:120-2015
37
Pre-treatment requires that the lime and water be added at least 4 hours prior to the addition
of the foamed bitumen. The treated material must be placed in an air-tight container to retain
moisture. However, due to the hydration process, the moisture content should always be
checked and, if necessary, adjusted prior to adding the bitumen stabilising agent.
A1.4 Mixing the Prepared Samples with Foamed Bitumen
Step 1 Place the required quantity of sample into a suitable mixing container
(capacity 10kg).
Step 2 Determine the dry mass of the sample using equation A1.1

¸
¸
¹
·
¨
¨
©
§
¸
¸
¹
·
¨
¨
©
§
+
=
−
−
100
1
dry
air
dry
air
sample
W
M
M
[Equation A1.1]
where Msample
= dry mass of the sample [g]
Mair-dry
= air-dried mass of the sample [g]
Wair-dry
= moisture content of air-dried sample [% by mass]
Step 3 Determine the required mass of active filler (lime or cement) using equation
A1.2.
( )
sample
Add
Cement M
C
M ∗
=
100
[Equation A1.2]
where MCement
= mass of lime or cement to be added [g]
Cadd
= percentage of lime or cement required [% by mass]
Msample
Step 4 Determine the percentage water to be added for optimum mixing
moisture content as calculated using equation A1.3. The mass of water to be
added to the sample is then determined using equation A1.4.
)
1
5
.
0
*
( −
−
−
= − OMC
dry
air
OMC
add W
W
W
W [Equation A1.3]
( )
Cement
sample
add
Water M
M
W
M +
∗
=
100
[Equation A1.4]
where Wadd
= water to be added to sample [% by mass]
WOMC
= optimum moisture content [% by mass]

IRC:120-2015
38
Wair-dry
= water in air-dried sample [% by mass]
Step 5 Mix the material, active filler and water in the mixing bowl until uniform.
Note: Inspect the sample after mixing to ensure that the mixed material is not packed against the
sides of the mixer. If this situation occurs, mix a new sample with a lower moisture content.
Check to see that the material mixes easily and remains in a “fluffy” state. If any dust is
observed at the end of the mixing process, add small amounts of water and remix until a
“fluffy” state is achieved with no dust.
Step 6 Determine the mass of foamed bitumen to be added using equation A1.5:
( )
Cement
Sample
add
Bitumen M
M
B
M +
∗
=
100 [equation A1.5]
where MBitumen
= mass of foamed bitumen to be added [g]
Badd
= foamed bitumen content [% by mass]
MCement
Msample
Step 7 Set the timer for bitumen addition according to the following formula:
¸
¸
¹
·
¨
¨
©
§
∗
=
Bitumen
Bitumen
Q
M
factor
T [equation A1.6]
where T = time to be set for foaming [s]
MBitumen
= mass of foamed bitumen to be added [g]
QBitumen
= bitumen flow rate (See A1.1.1) [g/s]
factor =
compensation for bitumen losses on mixing arm and bowl of the Hobart
mixer. Experience shows that a factor of 1,1 is generally required. This
factor is taken as 1.0 with the pugmill mixer.
Step 8 Position the mechanical mixer adjacent to the foaming unit so that the foamed
bitumen can be discharged directly into the mixing bowl.
Step 9 Start the mixer and allow it to mix for at least 5 seconds before discharging the
required mass of foamed bitumen into the mixing bowl. Continue mixing for a
further 30 seconds after the foamed bitumen has discharged into the mixer.
Step 10 Determine the mass of water required to bring the sample to 90% of the optimum
moisture content using equation A1.7.
( )
Cement
Sample
Sample
OMC
plus M
M
W
W
M +
∗
−
=
100
9
.
0
[Equation A1.7]

IRC:120-2015
39
where M plus
= mass of water to be added [g]
WOMC
= optimum moisture content [% by mass]
Wsample
= moisture content of prepared sample [% by mass]
Msample
Mcement
Step 11 Add the additional water and mix until uniform.
Step 12 Transfer the foamed bitumen treated material into a container and immediately
seal the container to retain moisture. To minimise moisture loss from the prepared
sample, manufacture briquette specimens as soon as possible.
Repeat the above steps for at least four different foamed bitumen contents.
A1.5 Manufacture of 100 mm Diameter Briquette Specimens
Step 1 Prepare the Marshall mould and hammer by cleaning the mould, collar, base-plate
and face of the compaction hammer. Note: the compaction equipment must not be
heated but kept at ambient temperature.
Step 2 Weigh sufficient material to achieve a compacted height of 63.5 mm ± 1.5 mm
(usually 1.15 kg is adequate). Poke the mixture with a spatula 15 times around the
perimeter and 10 times on the surface, leaving the surface slightly rounded.
Step 3 Compact the mixture by applying 75 blows with the compaction hammer (taking
care to ensure the continuous free fall of the hammer).
Step 4 Remove the mould and collar from the pedestal and invert (turn over).
Replace it on the pedestal and press down firmly to ensure that it is secure
on the base plate. Compact the other face of the briquette with a further 75
blows.
Step 5 After compaction, remove the mould from the base-plate and extrude the briquette
by means of an extrusion jack
Note: With certain materials lacking cohesion, it may be necessary to leave the specimen in the
mould for 24 hours, allowing sufficient strength to develop before extracting.
A1.6 Curing the Briquette Specimens
Place the briquettes on a smooth flat tray and cure in a suitable oven at 40°C until a constant
mass has been achieved (normally 72 hours in a properly-packed forced-draft oven is
required). Remove from oven after curing and allow to cool to 25°C.

IRC:120-2015
40
A1.7 Determination of Bulk Density
After cooling, for each briquette:
Step 1 Determine the mass.
Step 2 Measure the height at four evenly-spaced places around the circumference and
calculate the average height.
Step 3 Measure the diameter.
Step 4 Calculate the bulk density using equation A1.8
10000
4
2
.
∗
∗
∗
∗
=
h
d
M
BD
Briq
π
[Equation A1.8]
where BD = bulk density [kg/m³]
MBriq.
= mass of briquette [g]
h = average height of briquette [cm]
d = diameter of briquette [cm]
Exclude from further testing any briquette whose bulk density differs from the mean bulk
density of the batch by more than 50 kg/m3
.
Note: The bulk density can be verified by using the “weigh-in air / weigh-in water” method
A1.8 Strength Test Procedures
A1.8.1 Determination of Indirect Tensile Strength (ITS)
The ITS test is used to test the briquettes under two different moisture conditions: dry and
soaked. The ITS is determined by measuring the ultimate load to failure of a briquette that
is subjected to a constant deformation rate of 50.8 mm/min on its diametrical axis. The
procedure is as follows:
Step 1 Place the briquette onto the ITS jig. Position the sample such that the loading
strips are parallel and centred on the vertical diametrical plane.
Step 2 Place the transfer plate on the top bearing strip and position the jig assembly
centrally under the loading ram of the compression testing device.
Step 3 Apply the load to the briquette, without shock, at a rate of advance of 50.8 mm per
minute until the maximum load is reached. Record the maximum load P (in kN),
accurate to 0.1 kN.
Step 4 Immediately after testing a briquette, break it up and take a sample of approximately
1000 g to determine the moisture content (Wbreak
).

IRC:120-2015
41
Step 5 Calculate the ITS for each briquette to the nearest 1kPa according to equation
A1.9:
1000
2
∗
∗
∗
∗
=
d
h
P
ITS
π
[Equation A1.9]
where: ITS = Indirect Tensile Strength [kPa]
P = maximum applied load [kN]
h = average height of the specimen [cm]
d = diameter of the specimen [cm]
Step 6 To determine the soaked ITS, place the briquettes under water at 25 °C ± 1°C
for 24 hours. Remove briquettes from water, surface dry and allow to stand on
a draining board at 25 °C ± 1°C for 30 minutes. Repeat steps 1 to 5 for each
briquette.
Step 7 Determine the Unsoaked ITS (ITSDRY
) and Soaked ITS (ITSSOAKED
) for each batch
of briquette specimens by calculating the respective averages.
100
.
∗
=
DRY
SOAKED
ITS
ITS
TSR [Equation A1.10]
A1.9 Interpretation of Test Results
To determine the “optimum foamed bitumen content”, plot the ITSDRY
values, the ITSSOAKED
values and the TSR values (three curves) versus the added foamed bitumen (see example
below in Fig. A1.2).
The foamed bitumen added value that best meets the desired properties is regarded as the
optimum foamed bitumen content. The desired properties are project specific, taking into
account the type of material that is stabilised with foamed bitumen and the moisture regime.
As a guideline, the minimum ITSDRY
value for all pavements with a structural capacity
in excess of 0.3 million ESALs shall be 225 kPa and Soaked ITS should be 100 kpa.
Minimum Strength Requirement of RBM Mixes for foam Bitumen.
Strength Test Specimen diameter Minimum strength, KPa
ITSdry
, 25°C 100 mm 225 kPa
ITSwet
25°C 100 mm 100 kPa

IRC:120-2015
42
Gradation of RBM Mixes (IRC 37-2012)
Sieve size, mm %passing
45 100
37.5 87-100
26.6 77-100
19 66-99
13.2 57-87
4.74 33-50
2.36 25-47
0.60 12-27
0.3 8-21
0.075 2-9
The recommended TSR values for different climatic conditions and terrain are shown in the
table below.
Terrain / drainage
conditions
Mean Annual Rainfall (MAR) in mm
Arid
MAR 300
Dry
300 MAR 600
Moderate
600 MAR 1000
Wet
MAR 1000 mm
Rolling/well drained 25 50 60 70
Flat/poorly drained 50 60 70 80
ITS value at the optimum foamed bitumen addition can be used in Fig. A1.3 to obtain an
indicative value for the Structural Layer Coefficient and Resilient Modulus value for evaluating
the structural capacity of the rehabilitation proposal. Using this Fig., the input values for
pavement design for the example in Fig. A1.2 would be:
Structural layer coefficient: 0.27 per inch
Resilient modulus: 1600 MPa initial/900 MPa-1000 MPa steady state

IRC:120-2015
43
Fig. A1.3 Structural Guidelines for Foamed Bitumen Stabilised Material
Notes 1. All materials classified as A - 4 or lower to be pretreated with hydrated lime
2. Cement at nominal 1% to be added to all materials with PI 10 and CBR 45
3. Where required, non-plastic fine material to be added to increase the percentage passing
the 0.075mm sieve to achieve a minimum of 5%.
4. The following Tensile Strength Retained (%) requirements are recommended;
1 10 100
Soaked CBR value at Specified Density
A - 1 - a
A - 1 - b
A - 3
A - 2 - 4 A - 2 - 5
A - 4
A - 5
A - 6
A - 7 - 5 A - 7 - 6
41
/2 4
31
/2 3
4 31
/2
3 21
/2
A - 2 - 6 A - 2 - 7
AASHTO CLASSIFICATION OF NATURAL
MATERIAL BEFORE STABILISATION
EXPECTED APPLICATION RATE OF
FOAMED BITUMEN FOR
STABILISATION ( % by mass)
100 500
150 400
300
0.26
0.16 0.30 0.35
0.051 0.063 0.103 0.120 0.140
0.13
STRUCTURAL LAYER COEFFICIENTS AFTER STABILISATION
per cm
per inch
Indirect Tensile
Strength (kPa)
ANTICIPATED MATERIAL CHARACTERISTICS AFTER STABILISATION
Note: 1.
2.
200
0.21
0.083
500 2500
750 2000
1500
Initial Stiffness
Phase 1 (MPa)
1000
1050
450 950
800
Steady Stiffness
Phase 2 (MPa)
600
INDICATIVE STIFFNESS
For design traffic greater than 300 000 ESAL's the Indirect Tensile Strength (ITS) value
should always be obtained from the foamed bitumen mix design.
See table below for appropriate Tensile Strength Ratio (TSR)
250

IRC:120-2015
44
Appendix II to Annex 1
Quality Assurance Testing For Foamed Bitumen Stabilised Layers
A2.1 Scope
ThisAnnexure covers the requirements for monitoring the quality of foamed bitumen stabilised
layers and describes the routine tests to be carried out together with the frequency of such
testing.
A2.2 Daily Production Record
Daily production records shall be kept for detailing the production achieved.
A2.2.1 In-situ Treatment:
The following details shall be included for each recycled cut:
- cut number
- start and end chainage;
- depth of recycling;
- width of overlap(s) with previous cut(s);
- temperature of the bitumen;
- the foaming characteristics of each tanker-load of bitumen used;
- temperature of the material exposed on the milled-out floor; and
- the quantity of bitumen and filler consumed.
A2.2.2 In-plant Treatment:
The following details shall be included:
a) Production (where different blends were mixed, by blend)
- blend proportions and description of materials in the mix;
- application rates for bitumen and filler;
- temperature of the input materials and bitumen;
- the foaming characteristics of the bitumen used;
- tonnage of material treated and destination (stockpile and/or site); and
- reconciliation of actual consumption of bitumen and filler;

IRC:120-2015
45
b) Location of where the treated material was used on the project
- start/end chainages and width of paving;
- thickness of paved layer (after compaction);
- ambient temperature whilst paving; and
- temperature of the treated material when paved;
A2.2.3 As-built Data Records: Records shall be compiled which will schedule the daily
production data, as above, together with the results of all relevant quality assurance testing
for that particular day’s production.
A2.3 Quality Requirements
The material/structural properties to be controlled and the frequency of testing are:
Material/
Structure
Test Test Method Quantity No of tests
(minimum)
Bitumen Penetration grade
Foaming
characteristics
Delivery ticket
Visual – see below
Per tanker 1
Bitumen stabilised
layer
Layer thickness Measurements See below
Compaction IS 2720 (Part 28) Batch (note 1) 4
Foamed bitumen
stabilised material
Moisture content
determination
IS 2720 (Part 2) Batch (note 1) 4
Moisture/density
relationship
IS 2720 (Part 8) Batch (note 1) 1
Strength
characteristics
ITS – see below Batch (note 1) 2
Note 1: A Batch shall constitute a day’s work or as determined by the Engineer.
A2.3.1 Foaming characteristics
The test nozzle on the in-situ recycler or in-plant mixer shall be used to check the foaming
characteristics of each tanker-load of bitumen that is consumed.Aquantity of foamed bitumen
is injected from the test nozzle into a straight-sided container (normally a 5-second sample).
The half-life is measured by taking the time for the foamed bitumen to reduce in volume
to half the height of the maximum expansion noted in the container. The container is then
set aside for at least 30 minutes or until the foamed bitumen has subsided completely and

IRC:120-2015
46
the unexpanded volume of the quantity of bitumen injected into the container is noted. The
expansion ratio is the ratio of the maximum expansion to the unexpanded volume where the
unexpanded volume is taken as one unit.
A2.3.2 Depth of Recycling/Thickness of the Compacted Layer
The thickness of the completed layer shall be determined at each density test location from
physical measurements of the excavated hole. In addition, 100 mm diameter cores may be
extracted and measured after a curing period of at least two weeks.
A2.3.3 Compaction of the Completed Layer
The in situ density of the full thickness of the compacted layer shall be determined using the
sand replacement method (IS 2720 (Part 28)).
A2.3.4 Strength Characteristics from Field Samples
The quality and uniformity of the foamed bitumen stabilised layer shall be assessed from
samples taken on site, before compaction is applied. At least one bulk sample (±100 kg) shall
be taken from the full depth of the layer for every 1500 m² of treated material. All samples
must be retained in sealed bags for immediate transport to the laboratory. Field samples
shall be taken to the laboratory within two hours of sampling and 100 mm diameter briquette
specimens manufactured within four hours of being sampled. The procedures described
below shall be followed.
A2.3.4.1 Determination of the Moisture/Density Relationship
The Maximum Dry Density and Optimum Moisture Content (OMC) are determined from
a representative sample as per the moisture-density relationship test (IS 2720 (Part 8)).
(Generally one test per day is undertaken, unless a significant change in the material blend
is noted, demanding that one test per material blend is carried out.)
A2.3.4.2 Manufacturing Briquette Specimens
The material for manufacturing the briquette specimens shall be prepared as follows;
i) Determine the moisture content of the field sample.
ii) Weigh out a 10 kg sample (sufficient for manufacturing 6 briquettes).
iii) Sieve the sample through the 19 mm sieve and determine the mass retained on the
19 mm sieve.
iv) Using a portion of the remaining field sample, extract the material retained on the
12.5 mm sieve but passing the 19 mm sieve.

IRC:120-2015
47
v) Weigh out an amount equal to the mass of material retained on the 19 mm sieve from
the original 10 kg sample and add this to the sample such that the mass once again
totals 10 kg.
vi) Adjust the moisture content of the sample to approximate the OMC.
vii) Manufacture six 100 mm diameter briquettes following the procedures described
under Item A1.5 in Annexure 1.
A2.3.4.3 Curing the Briquette Specimens
The procedures described under Item A1.6 in Annexure 1 shall be followed for curing the
briquettes.
A2.3.4.4 Determination of Bulk Density
Follow the procedures described under Item A1.7 in Annexure 1 for determining the bulk
density of each briquette.
A2.3.4.5 Determination of the Indirect Tensile Strength (ITS)
The procedures described under Item A1.8 in Annexure 1 shall be followed for determining
the ITSDRY and ITSSOAKED values and the resulting TSR value. These values are then
used to determine whether the material has met the minimum specified requirements.
A2.3.5 Strength Characteristics from Core Specimens
Not sooner than 21 days after completing the foamed bitumen stabilised layer, 100 mm
diameter core samples may be extracted from the full thickness of the layer and tested for
ITS values
A2.3.5.1 Extracting Core Samples
Only core barrels in good condition shall be used to extract samples of foamed bitumen
stabilised material. A minimum amount of water shall be added whilst drilling and the rate
of penetration of the barrel will be sufficiently slow to prevent damaging the sample. After
extraction, core specimens shall be handled with care to prevent breakage.
A2.3.5.2 Cutting Core Specimens
A rotary saw fitted with a large diameter diamond-tipped blade shall be used to cut 63 mm
high specimens from the portion of the core that suffered least damage during extraction and
handling. Where possible, more than one specimen should be cut from each core sample.
A2.3.5.3 Curing the Core Specimens
The procedures described under Item A1.6 in Annexure 1 shall be followed for curing the
core specimens.

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A2.3.5.4 Determination of Bulk Density
The procedures described under Item A1.7 in Annexure 1 shall be followed for determining
the bulk density of each core specimen.
A2.3.5.5 Determination of the Indirect Tensile Strength (ITS)
The procedures described under Item A1.8 in Annexure 1 shall be followed for testing the
core specimens to determine the ITSDRY
and ITSSOAKED
values and the resulting TSR value.
These values are then used to determine whether the material has met the minimum specified
requirements.
Note. Where the ITS results for briquette specimens are in conflict with those obtained from core
specimens, the core specimen results after drying sufficiently (to below 75% of the OMC),
the shape of the original surface shall be reinstated by grader and compacted to achieve a
nominal 95% of the maximum dry density determined as per IS 2720 (Part 8). Thereafter, the
recycling / stabilisation work may proceed.

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Appendix III to Annex 1
Managing the reclaimed bituminous materials (RBM)
A 3.1 Managing the Reclaiming Process
RBM may be obtained from several sources. The most common method is through cold
milling operations, also known as cold planning/ Milling. Two other sources of RBM are full-
depth pavement demolition and bituminous plant waste. This section discusses the different
types of RBM sources.
A 3.2 Plant Waste
All bituminous plant operations generate some waste during plant start-up, transition
between mixes, and clean-out. Generally, start-up and shut-down plant wastes have
very low bituminous contents. Another form of waste is mix rejected from a project due
to incomplete coating or due to the mix temperature being too high or too low for the job.
Other situations that may result in wasted mix include trucks loaded with too much mix
to finish the job or mix that could not be placed due to inclement weather. These waste
materials are often stockpiled for later processing into a recyclable material. Since these
waste mixes have not been subjected to environmental aging from years of service, the
bituminous binder is less aged than RBM recovered from a road. Waste materials also
have fewer fines than other sources of RBM since it was not milled or broken up during
demolition. However, waste materials must be thoroughly mixed and processed to make
them into uniform, recyclable materials. Waste materials are often combined with other
sources of RBM in multiple-source stockpiles. Processing RBM from multiple sources is
discussed in greater detail in the next section.
A 3.3 Contamination
It is important that stockpiles be kept free of contaminants from the beginning. It easy to
understand how bad perceptions of RBM form when there is dirt, rubbish, or vegetation
in RBM stockpiles, or when trash is found in the mix when it shows up on the job site
or pops out of the pavement a few days after paving. Treat RBM stockpiles as the most
valuable material on the plant yard—because they are. Truck drivers bringing materials
onto the plant yard must be clearly instructed where to dump their loads so that unwanted
construction debris does not end up in the RBM stockpile and instructed that they should
clean the truck beds before hauling millings or useable RBM. The plant QC personnel
and the loader operator should also continuously monitor unprocessed and processed
RBM stockpiles to make sure they do not contain deleterious materials. If contaminants
are found, dig them out immediately so that they are not covered up with other RBM
brought onto the yard.
A 3.4 Processing and Crushing RBM
The basic goals of processing RBM are to

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1) create a uniform stockpile of material from a collection of different RBM materials
from various sources,
2) separate or break apart large agglomerations of RBM particles to a size that can be
efficiently heated and broken apart during mixing with the virgin aggregates,
3) reduce the maximum aggregate particle size in the RBM so that the RBM can be
used in surface mixes (or other small nominal maximum aggregate size mixtures),
and
4) minimize the generation of additional P 200 (i.e., dust).
A 3.5 Processing Milling Material.
Milled Material stock pilled after Milling
Millied Material. from a single project are usually very consistent in gradation, bituminous
content, aggregate properties, and binder properties. Therefore, processing millings may
only be necessary to achieve Goals #2 or #3. However, as noted previously, a common
limitation to increasing RBM contents in bituminous mixtures is the dust content in the RBM.
Since milled RBMs already contain appreciable amounts of P 200 (typically between 10%
and 20%) due to the milling of the material from the roadway, it is best to minimize further
crushing of milled RBM whenever possible. Therefore, when a contractor obtains a large
quantity of millings from a single project, it is considered a best practice not to further crush
this material, but rather to use it “as-is” in mix designs or to screen the millings to remove
larger particles.

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Asphalt material Reclaimed by Milling Machine
A 3.6 Millings: Recommended Processing Options
1. Receive millings from project.
2. Sample and test a few locations of the millings stockpile to determine the as-received
gradation and check the maximum aggregate size.
3. If the maximum aggregate size of the as-received millings is small enough to use in
the desired mix design(s), do not further process the millings.
4. If maximum particle size is too large for desired mix(es), then either fractionate the
RBM over a screen equal to or smaller than the NMAS of desired mix(es). Stockpile
the fine RBM (portion passing through the screen) and test for properties, as described
in Section
a. Stockpile the coarse RBM fraction(s) into separate stockpile(s) for use in other,
larger NMAS mixes, or
b. crush the millings so that they will pass the desired screen size.
This is the least desirable option because it will result in more uncoated faces of RBM
particles and generate additional dust, which can severely hamper how much of the crushed
RBM can be used in mix designs. When a contractor wants to increase RBM contents but is
often limited by VMA requirements or the dust-to binder ratio during mix designs, Para 4 must
become a primary consideration in his RBM-processing plan.

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A 3.7 Processing RBM from Multiple Sources
RBM materials from multiple sources that have different compositions must be processed to
create a uniform material suitable for use in a new bituminous mixture. All around the world,
contractors have found that they can make a very uniform and high quality RBM from a
combination of pavement rubble, millings, and wasted mix. The key to achieving a consistent
RBM from multiple sources is careful bending as part of the processing operations.Abulldozer,
excavator, or similar equipment should be used to blend materials from different locations in
the multiple-source RBM stockpile as it is fed into the screening and crushing operation. This
will tend to “average-out” variations in the RBM from different sources. The site WMM Plant
should be used for effective blending of the RBM to obtain homogeneous mix.
A 3.8 Screening RBM during Processing
Since crushing RBM will create more aggregate fines, it is best to set up the crushing
operation so that the RBM is screened before it enters the crusher. This will allow the finer
RBM particles that pass through the screen to bypass the crusher. Fig. 8 shows a portable
RBM crushing unit that is equipped with a screen deck in line before the crusher. Only the
RBM particles retained on the screen will pass through the crusher.
Some RBM crushing units are set up so that all of the RBM is conveyed from the feeder bin
into the crusher, followed by a recirculation circuit after the crusher. The recirculation circuit
is designed to return larger particles that do not pass through the screen back to the crusher.
However, since all of the material must go through the crusher in the first pass, there is a
good chance that breakdown will occur for some smaller particles that did not need to be
reduced in size.
A 3.9 Crusher Types
A variety of crusher types are used for crushing RBM. Many contractors have found that the
best type of RBM crushers are Track Mounted / horizontal-shaft impactors (HSI) with inbuilt
pre-screen and inbuilt product screen so that desired over size product can be sent back to
the crusher for further crushing to produce desired aggregate gradation.
The speed and clearance of hammer mill crushers can be adjusted to reduce aggregate
crushing. Some contractors have used milling machines to crush stockpiled RBM. There may
be a risk of the milling machine overturning since the stockpile is uneven and may not provide
stable support for the heavy machine. No data are available regarding the effectiveness of
this method of processing in terms of size reduction or consistency of the RBM. However
these are subject to the following conditions:
Compression-type crushers such as jaw crushers, and cone crushers also are found effective
for fine sizing RBM. Hammer mill crushers tend to generate more fines due to the retention
of the material in the chamber. The speed and clearance of hammer mill crushers can be
adjusted to reduce aggregate crushing. Some contractors have used milling machines to
crush stockpiled RBM. There may be a risk of the milling machine overturning since the

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stockpile is uneven and may not provide stable support for the heavy machine. No data are
available regarding the effectiveness of this method of processing in terms of size reduction
or consistency of the RBM. However these are subject to the following conditions:
A 3.10 Weather
Moisture and temperature can affect crushing and screening of RBM. When the RBM
is wet and/or temperatures are hot, RBM will be stickier and tend to build up in feeders
and crushers, blind screens, and RBM fines will stick to belts and accumulate under
conveyors. Not only does this require more maintenance of RBM processing units and
RBM feeder systems for mix production, it can also affect the gradation and bituminous
content of the RBM.
A 3.11 Fractionating
Fractionating is a process gaining popularity in which RBM is screened into typically two
or three sizes. The sizes are typically 20 mm x 10 mm, 10 mm x 4.75 mm, and less than
4.75 mm. In some cases, the plus 20 mm size material is returned to a crusher, and the
crushed material is then returned to the screening unit. The primary advantage of fractionating
RBM is that having stockpiles of different RBM sizes provides more flexibility in meeting mix
design requirements.
The decision of whether or not to fractionate RBM into different sizes should be the mix
producer’s choice and not a specification. Some agencies have recently begun to require RBM
fractionation for higher RBM contents. This type of method specification is not appropriate;
a better approach to assure consistency of RBM is to set limits on the variability of the RBM
stockpiles.
A 3.12 Moving the Processed RBM Stockpiles
In most cases, processed RBM will be moved from the location it is screened and/or crushed
to another location more convenient to feed into the bituminous plant. This is another
opportunity to remix the material and improve its consistency. Using the loader to dig into
the RBM stockpile at the processing unit at different locations around the pile and remixing
loads while building the stockpile at the final location can again be used to average out
variations.
A 3.13 Stockpiling to Minimize Segregation
As with virgin aggregates, there is a potential for RBM materials to become segregated in
stockpiles. This is a common problem when stockpiles are built using fixed conveyors that
allow the RBM particles to drop long distances to the stockpile. Larger particles have more
kinetic energy and will tend to roll down toward the bottom of the stockpile. This results in
more coarse particles with a lower bituminous content at the base of the stockpile and finer
higher bituminous content RBM in the top of the stockpile. This problem can be minimized
by using indexing-type conveyors that extend and raise the end of the conveyor as the size

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of the stockpile increases. If segregation is evident, a front end loader can be used to remix
the stockpile.
A 3.14 Stockpiling to Minimize Moisture
Moisture content of aggregates and RBM is a primary factor affecting a bituminous plant’s
production rate and drying costs. Some contractors have implemented creative approaches
to reducing moisture content in stockpiles. The best practice to minimize the accumulation of
moisture in stockpiles is to cover the stockpile with a shelter or building to prevent precipitation
from getting to the RBM. Second to that, it is a good practice to use conical stockpiles to
naturally shed rain or snow, and to place the stockpile on a paved and sloped surface to help
water drain from the pile. Irregular-shaped stockpiles with surface depressions that will pond
water should be corrected by shaping the pile as it is being built with the front-end loader or
a small dozer. However, the use of heavy equipment on the top of RBM stockpiles should
be minimized to avoid compaction of the RBM. Likewise, it is also recommended that RBM
stockpiles be limited to 3 m in height to reduce the potential for self-consolidation of the
stockpile.
A 3.15 In-line RBM Crushers or Crusher Circuits
RBM crushers or crushing circuits that are built into the bituminous plant’s RBM feed line can
change the gradation of the RBM material being fed into the mix. Gradation test results on
the stockpiled RBM then become meaningless, and the quality control personnel will have to
make unnecessary, and probably substantial, mix adjustments to get the mix gradation and
volumetric properties in specification during production start-up. In many cases, this could
require a reduction in the RBM content in order to meet the quality control tolerances for the
mix.
In-line roller crushers (also known as lump-breakers) and reduced-speed impact crushers
designed to break up agglomerations of RBM rather than change the gradation are used
by some contractors. It is recommended to conduct a simple extracted gradation check of
RBM samples before and after the in-line crusher to determine if it is breaking down the RBM
aggregate.

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A 3.16 Advantages and Disadvantages of Different RBM Processing Options
Table 1 lists possible advantages and disadvantages of different RBM processing options.

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A 3.17 Sampling and Testing the RBM
This section provides guidance on the best methods and practices for sampling and testing
RBM as part of a quality management program. A well-executed sampling and testing
plan for RBM is necessary to assess the consistency of the RBM stockpiles and to obtain
representative properties for use in mix designs.
A 3.18 RBM Variability
A common misconception exists that RBM stockpiles are highly variable and, thus, using
higher RBM contents in new bituminous mixes will lead to more variability in the mixtures.
However, well-managed RBM stockpiles have a more consistent gradation than virgin
aggregates considering that RBM obtained from a single milling project in which the pavement
was constructed of mixtures subject to high quality assurance standards, it is no surprise
that the millings would have a consistent gradation, bitumen content, and binder properties.
Less expected is how consistent RBM processed from multiple sources can also be just as
consistent in gradation and bitumen content as millings.
Sampling and Testing Frequency
Sampling for at least one set of tests per 1,000 tons of RBM is considered a best practice.
This is generally more frequent than is required for virgin aggregates, but is appropriate for a
component that will comprise a large portion of a bituminous mixture. A minimum of 10 tests
should be performed on a RBM stockpile to yield good statistics for consistency analyses.
A 3.19 Sampling Method
It is recommended that RBM stockpiles be sampled as they are being built at the location
where they will be fed into the bituminous plant. Samples from the different locations should not
be combined since the results from the different locations will be used to calculate variability
statistics. Sampling at the time the stockpile is built will be easier and more representative
of the stockpile compared to samples taken later, after a crust forms on the RBM stockpile.
When a RBM stockpile has been in place for a while, it is generally difficult to dig into with
a shovel. The best way to sample existing RBM stockpiles is with the assistance of a front-
end loader, as described in Section X1.2 of AASHTO T2 or ASTM D 75-03. This method is
described and illustrated below.
1. Use a front end loader to dig into to the ready to use RBM stockpile.
2. Empty the bucket on a clean surface to form miniature sampling stockpile
3. Use the loader to back blade across the top of the mini stockpile to create a flat
surface
4. Mini stockpile ready to be sampled
5. Use a square-end shovel to obtain samples from the surface of the mini stockpile

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6. Sample from three locations over the surface of the mini stockpile
7. Combine samples taken from the same mini stockpile. This sample will later be
divided into test portions
8. Repeat this process to obtain samples at other locations around the RBM stockpile.
Do not combine samples from different locations.
A 3.20 Test Methods
For mix designs using RBM, the data needed from tests on the RBM are
1) bituminous binder content of the RBM,
2) gradation of the aggregate recovered from the RBM,
3) bulk specific gravity of the RBM aggregate,
4) consensus properties of the aggregate recovered from the RBM, and
5) (for high RBM contents) the RBM bituminous binder properties.
6) more than 35% RBM cannot be used if fine milling has been carried out at site.
In some cases, additional aggregate tests may be necessary. For example, if the RBM is to
be used in a surface mix for high-speed traffic, some agencies may require tests to evaluate
the polishing or mineralogical composition of the RBM aggregate. Typically, source properties
such as LA abrasion and sulfate soundness tests are not necessary since it is unlikely that
the coarse aggregates in the RBM would have come from sources not originally approved by
the state agency.
A recent joint study by the University of Nevada Reno and NCAT examined several options
for testing RBM to determine the best methods for determining many of the properties noted
above. Three methods were used to determine bitumen contents and recover the aggregates
for aggregate property tests: the ignition method, the centrifuge extraction method, and the
reflux extraction method. Trichloroethylene was used as the solvent in the centrifuge and
reflux methods. The results of the study indicate that
• The ignition method yielded the most accurate bitumen contents for the RBM and
provided the lowest testing variability compared to the solvent extraction methods.
• The centrifuge extraction method had the smallest affect on the gradations of the
recovered aggregate.
• The combined bulk specific gravity of the aggregates recovered by the ignition
method was closest to the original materials, except for the soft limestone aggregate.
In that case, the aggregate recovered from the centrifuge extraction was closest to
the original material.

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• The sand-equivalent and fine-aggregate angularity values for aggregates recovered
from all three methods were different from the original materials. No consistent biases
were evident to warrant making adjustments to the tested results.
• LA abrasion values for aggregates recovered from the centrifuge extraction were
closest to the original values.
Additional tests on the extracted and recovered bitumen binder from the RBM may be required
for mix designs that will contain more than 25% RBM. Current best practices for determining
RBM binder properties are described in Chapter 3 of NCHRP Report 452. Several research
studies are currently in progress to develop alternative procedures for determining RBM
binder properties and methods for selecting the grade of the virgin binder for high RBM
content mixtures:
A 3.21 Methods for Determining RBM Bitumen Contents and Recovering Aggregates
Two options are recommended for determining RBM bituminous content and recovering
aggregates: the ignition method and solvent extractions. Both methods have advantages and
disadvantages. The following sections discuss the associated advantages and disadvantages
of these methods.
A 3.22 Ignition Method
The most popular method for determining RBM bitumen contents and recovering aggregates
for other tests is the ignition method, AASHTO T 308 or ASTM D 6307. Advantages of the
ignition method include quick results, little testing time, and no solvents are needed. One
issue with this method is that in order to obtain an accurate bituminous content for a sample,
it is necessary to know the aggregate correction factor. For virgin materials, the aggregate-
correction factor is determined by testing samples with a known bitumen content. The
difference between the known bitumen content and the test result for the prepared samples
is the aggregate-correction factor. However, for RBM, it is not possible to have a sample with
a known bitumen content and, therefore, not possible to determine the aggregate-correction
factor. Fortunately, aggregate-correction factors are typically consistent over time when the
aggregate materials used at the location are from the same quarry or deposits. Therefore, a
historical average aggregate correction factor of the materials at a location can be used as
the aggregate correction factor for the RBM.
RBM aggregates recovered from the ignition method can be used for gradation analysis and
some other aggregate-property tests, but not all. Some aggregate types (e.g., dolomites)
can have significant changes in mass when heated to 1000°F in an ignition oven. Small
natural variations in the mineralogy of these aggregates create large variations in aggregate-
correction factors in the ignition oven (as high as 1% to 2%). Some agencies have altered
the test to reduce the ignition oven temperature to minimize this problem. However, in some
cases, agencies have elected simply to use other methods for determining bitumen contents
and recovering aggregates for bitumen mixes in their jurisdiction. In these locations, the
bitumen content for RBM samples should be determined using solvent extractions.

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Solvent Extraction
Solvent extractions with trichloroethylene or other solvents have been used for many decades
to determine bitumen contents of bitumen mixtures and as a method of recovering aggregates
for additional tests. However, use of the method has declined due to health and environmental
concernswiththechlorinatedsolvents.Normal-propylenebromideandsomenon-halogenated
(terpene or d-limonene based) solvents were found to be acceptable alternative solvents and
are permitted in AASHTO T 164, but some problems were reported with the effectiveness
of these solvents to remove polymer-modified bitumen binders. However, some agencies
and contractors continue to use solvent extractions due to problems with highly variable
ignition furnace aggregate correction factors or with the breakdown of certain aggregate
types. Depending on aggregate characteristics, solvency power of the solvent, and hardness
of the binder, solvent extractions may not remove all of the absorbed bitumen binder from the
aggregate. Based on the published precision information, the repeatability and reproducibility
of the ignition method are more than four times better than the solvent extraction method.
Aggregate Bulk Specific Gravity
An alternate approach to estimating the bulk specific gravity of the RBM aggregate discussed
in NCHRP Report 452 (6) was also evaluated in the UNRNCAT study. This approach begins
with conducting the maximum theoretical specific gravity tests (i.e., the Rice method) on
samples of the RBM following AASHTO T 209. The effective specific gravity of the RBM
aggregate is then calculated from the bitumen content and Gmm
values determined from tests
on the samples as follows.
The final step is to calculate the RBM aggregate bulk specific gravity using the formula:
where Pba
(bitumen absorption) and Gb
(binder specific gravity) have to be assumed. Historical
values for Pba
and Gb
for the materials used at each plant location should be reviewed to
determine if they have been consistent over time.
Advantages of this approach are that no solvent is needed (if the ignition method is used to
determine the RBM binder content), and the method is much faster than recovering the RBM
aggregate from the solvent extraction or ignition method and testing the aggregate specific
gravities using AASHTO T84 and T85, like any other aggregate. However, the accuracy of

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this method is highly dependent on how well the percentage of absorbed bitumen can be
estimated.
Due to the advantages, disadvantages, and limitations of the different methods for determining
bitumen contents, recovering RBM aggregates, and determining their properties, it is
necessary to have a couple options for testing. It is prudent for agencies and contractors to
cooperate in establishing the best methods for the materials in their region or jurisdiction. The
following flow charts present two reasonable approaches.
All test results should be recorded in a spreadsheet or software program to organize and
summarizethedata.Thedatabaseshouldincludestockpilename/description,dateofsamples,
and for each sample, the results for bitumen content, gradation of recovered aggregate, and
bulk specific gravity of the RBM aggregate. The spreadsheet should calculate the average
and standard deviation of each property. It is necessary to collect and analyze test results of
at least 10 RBM samples to estimate the statistics for the stockpile.
If more RBM is added to the stockpile, sampling and testing should continue at a frequency
of one set of tests per 1,000 tons of RBM. Table 2 shows guidelines for standard deviations
of key properties of RBM. The standard deviation statistic is a basic measure of variability.
The median sieve is the sieve closest to having an average of 50% passing. Typically, this is
the sieve with the largest standard deviation. In the example spreadsheet above, the median
sieve is the 2.36 mm sieve.
These values are based on data gathered from contractors using many of the best practices
in this document. Although excellent RBM-management practices are necessary to have
standard deviations within these limits, published reports and recent surveys show indicate
that they are attainable. If the variability of one or more properties exceeds the values in
Table 2, the stockpile management guidelines in this document may be helpful in reducing
the standard deviations. Also keep in mind that sampling practices can have a significant
effect on variability results.
Table 2. Variability Guidelines for RBM Stockpiles
RAP Property Maximum
Std. Dev. (%)
Asphalt Content 0.5
% Passing Median Sieve 5.0
% Passing 0.075 mm Sieve 1.0

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Annex 2
List of some Projects on Recycling carried out in India
1. The main carriageway section of Tumkur – Honnavar Highway, NH-206 near Tumkur
strengthened by Full Depth Reclamation (FDR) Technology with a Commercial
Cementitious Stabilizer. The pavement section is able to withstand heavy traffic.
FWD tests was done to verify design modulus and GPR test was done to check the
uniformity crack formation in cementitious layer.
2. The one side carriageway of Bangalore University in front of Civil Engineering
Department was strengthened by Cold Recycling Technology with a Commercial
Cementitious Stabilizer. The pavement section is able to withstand heavy traffic in
the night time as the road is connecting two major roads approaching Bangalore
city. The stretch was evaluated for roughness stiffness by MERLIN Geo-gauge
respectively.
3. Chennai Tada NH 5 Section total of 12 km with width of 8.75 m.
4. Baroda Halol phase 1 total length of 11 km recycled to a depth of 20 cm.
5. Baroda Halol Phase 2 the total section of 6 km was executed to a depth of 16 cm with
foam bitumen as binder.
6. Ahmedabad Mehsana 6 km of cold recycling to a depth of 160 mm under rehabilitation
by cold recycling using foam bitumen as binder.
7. Hot in-situ recycling of Mehrauli to Badarpur under Delhi PWD.
8. Recycling of roads in Delhi under Delhi PWD.

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REFERENCES
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6. Rehabilitation, Asphalt Recycling and Reclaiming Association, Annapolis, MD,
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7. Guideline Specifications for Cold Planing, Asphalt Recycling and Reclaiming
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8. J.D. Brock. Milling and Recycling, Technical Paper T-127. A Industries,
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12. Recycling Hot Mix Asphalt Pavements, Information Series 123, National Asphalt
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15. L. Flynn. “Surface Courses in Montana Now May Contain 25% RAP.” Roads and
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16. F.L. Roberts, P.S. Kandhal, E.R. Brown, D. Lee, and T.W. Kennedy. Hot Mix Asphalt
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Foundation, Lanham, MD, 1996.
17. E.R Brown, N.E. Murphy, and S. Mager. Historical Development of Asphalt Content
Determination by the Ignition Method, Proceedings of AAPT, Vol. 64, 1995.

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18. J.A. D’Angelo and T. Ferragut. Summary of Simulation Studies from Demonstration
Project No. 74: Field Management of Asphalt Mixes, Proceedings of AAPT, Vol. 60,
1991.
19. P.S. Kandhal, K.Y. Foo, and J.A. D’Angelo. Field Management of Hot Mix Asphalt
Volumetric Properties, ASTM Special Technical Publication 1299, 1996.
20. Evaluation of Long-Term Field Performance of Cold In-Place Recycled Roads: Field
and Laboratory Testing Final Report May 2007, Sponsored by the Iowa Highway
Research Board (IHRB Project TR-502) and the Iowa Department of Transportation
(CTRE Project 03-160)
21. Draft Report on “ Eco Friendly Road Technology using Natural Soil Stabilizer”
submitted to the Ministry of Environment Forests.
(The amendments to this document will be published in its periodical,
‘Indian Highways’ which shall be considered as effective and as part of
the code/guidelines/manual, etc. from the date specified therein)

IRC 120.pdf

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IRC 120.pdf