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Transcript of Lab and field eveluation of recycled cold mix
Laboratory and Field Evaluation of Recycled Cold Mixes I
Dissertation report on
“LABORATORY AND FIELD EVALUATION OF RECYCLED COLD MIXES”
Submitted in partial fulfillment for award of the degree of
MASTER OF TECHNOLOGY In
TRANSPORTATION ENGINEERING (2004-2006)
Submitted by: G.NARENDRA GOUD Under the guidance of
DR. SUNIL BOSE Head,
Flexible Pavements Division, CRRI-New Delhi
SHRI ARUN GAUR Lecturer
Department of Civil Engineering MNIT-Jaipur
DEPARTMENT OF CIVIL ENGINEERING
MALAVIYA NATIONAL INSTITUTE OF TECHNOLOGY
(DEEMED UNIVERSITY)
JAIPUR (RAJASTHAN)-302017
Laboratory and Field Evaluation of Recycled Cold Mixes II
CERTIFICATE
This is to certify that the Dissertation report entitled “LABORATORY AND
FIELD EVALUATION OF RECYCLED COLD MIXES” being submitted by
Mr. G. NARENDRA GOUD (College ID -046126) to the Department of civil
engineering, Malaviya National Institute of Technology-Jaipur, in partial fulfillment
for the award of Master of Technology in Transportation Engineering is a bona fide
work carried out by him under our guidance and supervision.
The contents of this dissertation, in full or in parts, have not been submitted to any
other institute or university for the award of any degree or diploma.
Place: New Delhi Date: / 6/ 2006
(Dr. SUNIL BOSE)
Head, Flexible Pavements Division,
CRRI-New Delhi
(Shri ARUN GAUR) Lecturer
Department of Civil Engineering MNIT-Jaipur
Laboratory and Field Evaluation of Recycled Cold Mixes III
ACKNOLEDGEMENTS I would like to express my sincere gratitude to Dr. P.K. Nanda, Director, Central Road Research
Institute, New Delhi for permitting me to carryout my dissertation work in Flexible Pavements
Division, CRRI.
It is most pleasant to express hearty gratitude to my external guide Dr Sunil Bose, Head flexible
pavements division-CRRI, who has given me the opportunity and under whose supervision I was
able to do my dissertation work. Words can not do much justice to the guidance and help given by
him.
I sincerely express my deep gratitude to my internal guide Shri. Arun Gaur, Lecturer, Department
of Civil Engineering and Shri. Girish shrma for their guidance and support.
I am very much thankful to Shri. Subhash Niyogi, Managing Director of Wirtgen India Private
Limited, for providing me all the facilities in carrying out the study. I am grateful to all the
employees of Wirtgen India Private Limited-Bangalore whoever helped me during my association
with the firm. And also I’m very thankful to Devendhar Singh Bisth, Quality control engineer,
Nagarjuna Construction Company (NCC) Pvt. Ltd. for aiding me the laboratory facilities at their
project site Bidadi-Bangalore.
Laboratory and Field Evaluation of Recycled Cold Mixes IV
My Hearty Gratefulness and thanks to Dr. Pawan Saluja, Shri. Gajender Kumar, Shri Manoj
Shukla, Dr. Sangitha and CRRI-Flexible Pavements Division staff for their encouragement,
technical guidance and support during my laboratory study.
I would like to thank Dr Rohit Goyal, Head Department of Civil Engineering, Malaviya National
Institute of Technology, Jaipur. for giving me the permission to do my dissertation work at CRRI.
I would like to thank Dr. Krishna Murthy, Head Department of Civil Engineering, Bangalore
University who has accepted immediately to conduct BBD study on the test track.
My special thanks to Shri. Pawan Kalla, Lecturer Department of Civil Engineering, Malaviya
National Institute of Technology, Jaipur and Shri. Sridhar Raju, Scientist, CRRI. who
encouraged and supported me to do my dissertation work at CRRI-New Delhi.
Last but never the least; I would like to state my deep gratitude for all the support given
required from time to time, by my parents and all my friends.
Once again I thank one and all who have helped me directly or indirectly in completion of
my dissertation work.
(G. Narendra Goud)
Laboratory and Field Evaluation of Recycled Cold Mixes V
ABSTRACT
In the dense populated cities like Delhi, where environmental pollution and Land fill problems are
of prime concerns in the recent years. In rapid developing countries like India, where conservation
and optimum utilization of the road building materials specially petroleum and mineral products
are an important issue. There is an immediate attention requirement towards the development and
implementation of Ecofriendly and cost effective pavement construction technologies. Through
application of these technologies the efficient use of existing and waste materials can be made
with out creating problems to the environment and at the same time meeting the quality
requirements of the pavements.
Advances in technology and techniques in the in recent years have made cold recycling an
increasingly popular and cost-effective pavement construction and maintenance technique. In the
present study an effort is made to study the laboratory and field behaviour of recycled cold mixes
with binders as an emulsion and foamed bitumen. The Marshall specimens were cast using
emulsion and foamed bitumen in combination with different types of fillers such as cement, lime
and fly-ash. The specimens were tested for density, Indirect Tensile Strength, Resilient modulus
and dynamic creep. Benkelman Beam deflection study was carried out on the pavement
constructed with recycled foamed bituminous mix after a period of three months from construction
and field cores were cut from the pavement and were investigated in the Laboratory. It was found
that the pavement constructed with foamed bitumen treated RAP was structurally sound and cores
cut from that pavement have shown higher ITS and MR values when compared with Laboratory
cast cores but they shown less creep stiffness and densities. In comparison with emulsion treated
RAP, foamed bitumen treated RAP shown higher density, ITS, MR and creep stiffness with same
aggregate and gradation.
Laboratory and Field Evaluation of Recycled Cold Mixes VI
CONTENTS
S.NO. TITLE Pg NO
1. INTRODUCTION......................................................................................................................1
1.1 General .................................................................................................................................1
1.2 Objectives.............................................................................................................................2
1.3 Scope of Work .....................................................................................................................2
1.4 Methodology Adopted .........................................................................................................2
2. LITERATURE REVIEW ..........................................................................................................3
2.1 Why Milling? .......................................................................................................................3
2.2 Why Recycling?...................................................................................................................3
2.3 Methods of Pavement Recycling .........................................................................................4
2.4 Candidates for Recycling .....................................................................................................5
2.5 Advantages of Cold Recycling ............................................................................................6
2.6 Bitumen Emulsion................................................................................................................7
2.7 Bitumen Emulsion Classification.........................................................................................8
2.8 Recycling With Bitumen Emulsion .....................................................................................9
2.9 Foamed Bitumen ................................................................................................................12
2.10 Characterization of Foamed Bitumen ..............................................................................13
2.11 Factors influencing foam properties ................................................................................14
2.12 Dispersion of foamed bitumen.........................................................................................16
2.13 Material suitability for foamed bitumen treatment ..........................................................17
2.14 Recycling with foamed bitumen ......................................................................................19
2.15 The benefits of foamed bitumen stabilisation ..................................................................26
2.16 Case studies......................................................................................................................29
Experience in India: .................................................................................................................29
2.16.1 Emulsion Cold Recycling Rehabilitation Project-Hyderabad ......................................29
2.16.2 Foam bitumen cold recycling rehabilitation project-Bangalore ...................................35
Experience in abroad:...............................................................................................................40
2.16.3 Emulsion Cold Recycling Rehabilitation Project. Citizen Court, Toronto, June 2003 40
Laboratory and Field Evaluation of Recycled Cold Mixes VII
2.16.4 Saudi Arabia – A desert road for heavy traffic .............................................................45
2.16.5 In-Plant recycling using milled asphalt bound with foamed bitumen ..........................47
3. LABORATORY AND FIELD STUDY ......................................................................................55
3.1 RAP and Mineral Aggregate Evaluation ...........................................................................55
3.2 Foamed Bitumen Characterization.....................................................................................55
3.3 Emulsion Testing ...............................................................................................................59
3.4 Mineral Aggregate Proportions..........................................................................................59
3.5 OMC Determination for Foamed Bitumen Treatment.......................................................64
3.6 OFC Determination for Emulsion Treatment ....................................................................65
3.7 Recycled Cold Mix Preparation with Foamed Bitumen ....................................................66
3.8 Recycled Cold Mix Preparation with Emulsion ................................................................69
3.9 Foamed bitumen and Bitumen Emulsion treated RAP Specimen testing..........................70
3.10 Benkelman Beam Deflection testing................................................................................76
4. RESULTS AND ANALYSIS .....................................................................................................77
4.1 Results of Foamed Bitumen Treated RAP Marshall Specimens .......................................77
4.2 Results of Emulsified Bitumen Treated RAP Marshall Specimens...................................85
4.3 Field and Laboratory Core Comparison.............................................................................89
4.4 Dynamic Creep Test Results Analysis...............................................................................90
5. CONCLUSIONS AND RECOMMENDATIONS ......................................................................92
6. APPENDICES ..........................................................................................................................93
Appendix 1: Material Sampling and blending .........................................................................93
Appendix 2: Mix Design Procedure for Bitumen Stabilised Materials ...................................95
Appendix 3: Strength Test Procedures...................................................................................105
7. REFERENCES.......................................................................................................................108
Laboratory and Field Evaluation of Recycled Cold Mixes VIII
LIST OF FIGURES
Figure 2.1: Example of fluid considerations for a bitumen emulsion stabilised material 10
Figure 2.2: Schematic diagram of foamed bitumen production 12
Figure 2.3: Bitumen Foam characterization 14
Figure 2.4: Foamed bitumen dispersion and binding in the treated mix 17
Figure 2.5: Material gradation envelops 18
Figure 2.6: A view of recycling process progress in Hyderabad 31
Figure 2.7: Aggregate Spread over the layer to be recycled to correct the Gradation 31
Figure 2.8: Recycling crew in action 32
Figure 2.9: Recycled layer after pre compaction 32
Figure 2.10: Compacting the recycled layer 33
Figure 2.11: Tack coat application over the recycled and compacted layer 33
Figure 2.12: Finished surface of the recycled layer 34
Figure 2.13: Loader used to load the materials in to the mobile plant 37
Figure 2.14: Cement and hot bitumen supplied to the plant 37
Figure 2.15: Recycled material being discharged in to the dumper 38
Figure 2.16: Recycled foamix being dumped in to the paver hopper 38
Figure 2.17: Initial compaction with vibrator roller 39
Figure 2.18: Final compaction with pneumatic tyred roller 39
Figure 2.19: Recycling option used 42
Figure 2.20: Emulsion tanker and recycler 42
Figure 2.21: Pre-compacted surface after 1st pass 43
Figure 2.22: Cold milling from kerb outwards 44
Figure 2.23: Pre-compacted surface after 2nd pass 45
Figure 2.24: Recycling of Shaybah Access road 46
Figure2.25: The Hartl Powercrusher PC 1270 I Impact crusher being used to crush the RAP
material 50
Figure2.26: The Wirtgen KMA 200 cold mixing plant utilized to dose and mix the binding
agents and water with the RAP 50
Laboratory and Field Evaluation of Recycled Cold Mixes IX
Figure 2.27: Vogele 1800 paving the foamed bitumen treated base material directly onto the
road as an overlay 51
Figure 2.28: Compaction done with HAMM HD O70V double drum Oscillation /
Vibration roller and HAMM GRW 18 pneumatic tyred roller 51
Figure2.29: The road surface being moistened with water during final compaction and
just before traffic is allowed onto the base course 52
Figure2.30: The longitudinal joint being moistened before paving of the second road-width52
Figure 2.31: Paving of the second road width and traffic on the freshly compacted material.
This layer was kept moist for the first couple of hours for curing purposes 53
Figure2.32: The finished cold recycled base course after being trafficked for several days 53
Figure2.33: The Tack coat applied by a hand sprayer on one half of the base course 54
Figure2.34: Paving and compaction of the 4 cm asphalt wearing course 55
Figure3.1: WLB 10- Wirtgen foamed bitumen lab kit 57
Figure3.2: Air pressure Influence on expansion ratio and half time of Foamed bitumen 58
Figure3.3: Bitumen temperature Influence on expansion ratio and half time of Foamed
bitumen 58
Figure3.4: Bitumen water content Influence on expansion ratio and half life time of Foamed
bitumen 59
Figure3.5: option1 gradation curves 62
Figure3.6: option2 gradation curves 62
Figure3.7: option3 gradation curves 63
Figure3. 8: option4 gradation curves 63
Figure3.9: samples of separated RAP and stone dust 64
Figure3.10: OMC determination 64
Figure3.11: OFC determination 65
Figure3.12: Mineral aggregates used in the study 66
Figure3.13: WLB10 laboratory plant used to produce foamed bitumen 66
Figure3.14: Pug-mill type mixer used to prepare foamix 67
Figure3.15: Hobart mixer used to prepare emulsion mixture 69
Figure3.16: Indirect Tensile Strength Testing Schematic diagram 70
Figure3.17: Specimen setup of Indirect Tension Test for Resilient Modulus 71
Laboratory and Field Evaluation of Recycled Cold Mixes X
Figure3.18: Specimen setup of dynamic creep testing 71
Figure3.19: Benkelman Beam rebound deflection variation with distance 76
Figure 7.1 Determination of optimum foaming water content 100
LIST OF TABLES Table2. 1: The major uses of bitumen emulsion 07
Table2. 2: Bitumen emulsion classification and their recommended application.
(IS 8887-2004) 08
Table2. 3: Foamed bitumen dispersion (ability to mix) 20
Table2. 4: Typical foamed bitumen contents relative to key aggregate fractions 21
Table2. 5: Tentative binder and additional treatment requirements 22
Table2.6: Comparison between different types of bitumen applications 28
Table3. 1: Sieve analysis of pulverized and air-dried RAP 55
Table3. 2: Sieve analysis of Stone Dust 55
Table3. 3: Air pressure Influence on expansion ratio and half time of Foamed bitumen 57
Table3. 4: Bitumen temperature Influence on expansion ratio and half time of Foamed
bitumen 58
Table3. 5: Study of Bitumen water content Influence on expansion ratio and half life time
of Foamed bitumen 58
Table3. 6: Tests on Emulsion 59
Table3. 7: Different options of aggregate proportions 60
Table3. 8: Option1 Material proportions 60
Table3.9: Option2 Material proportions 60
Table3.10: Option3 Material proportions 61
Table3.11: Option4 Material proportions 61
Table 3.12: Material calculations for foamix preparation 68
Table 3.13 Foamed bitumen Specimen test results 72
Table 3.14 Bitumen Emulsion Specimen test results 74
Table3.15: Dynamic Creep Test results 75
Table3.16: Deflection data (LHS, towards Karnataka cold Storage Pvt. ltd) 76
Laboratory and Field Evaluation of Recycled Cold Mixes XI
Table3.17: Deflection data (RHS, towards Karnataka cold Storage Pvt. ltd) 76
Table4.1: Maximum bulk density values from the Graphs 4.1(a, b, c) 77
Table 4.2: Maximum Resilient modulus (MR) values from the Graphs 4.2(a, b) 80
Table4.3: Maximum Resilient modulus (MR) values from the Graphs 4.3 (a, b) 81
Table4.4: Maximum Resilient modulus (MR) values from the Graphs 5.6(a, b) 82
Table 4.5: Maximum Dry Indirect Tensile Strength (ITS) values from the Graphs 4.5 (a, b, c) 83
Table 4.6: Maximum soaked Indirect Tensile Strength (ITS) values 83
Table4. 7: Maximum bulk density values From the Graphs 4.6 (a, b) 85
Table4. 8: Maximum Resilient Modulus values from the Graphs 4.7 (a, b) 86
Table 4. 9: Maximum Dry and Soaked Indirect Tensile Strength (ITS) values from the Graphs 4.8
(a, b) and 4.9 (a, b) 87
LIST OF GRAPHS Graph4. 1:( a, b, c) Variation of bulk density with foamed bitumen and filler 78
Graph4.2 :( a, b) Variation of Resilient Modulus with foamed bitumen and Cement 80
Graph4.3 :( a, b) Variation of Resilient Modulus with foamed bitumen and Lime 81
Graph4.4 :( a, b) Variation of Resilient Modulus with foamed bitumen and Fly-ash 82
Graph4.5: (a, b, c) Variation of dry ITS with foamed bitumen 84
Graph4.6 :( a ,b) Variation of bulk density with Bitumen Emulsion 85
Graph4.7 :( a, b) Variation of Resilient Modulus with Bitumen Emulsion 86
Graph4.8: (a, b) Variation of ITS with Bitumen Emulsion and Cement 88
Graph4.9 :( a, b) Variation of ITS with Bitumen Emulsion and lime 88
Graph4.10 :( a, b, c) Variation of Resilient Modulus, Bulk density and ITS in
different cores 89
Graph4.12 :( a, b, c) Variation of Accumulated axial strain with Number of cycles 90
Graph4.11 :( a, b) Variation of Accumulated axial strain with Number of cycles 91
Laboratory and Field Evaluation of Recycled Cold Mixes 1
_________________________________________CHAPTER 1
1. INTRODUCTION
1.1 General
In the dense populated cities like Delhi, where environmental pollution and Land fill problems are
of prime concerns in the recent years. In rapid developing countries like India, where conservation
and optimum utilization of the road building materials specially petroleum and mineral products
and energy are an important issues. The rehabilitation and up gradation of existing badly
distressed Pavements due to rapidly growing heavy vehicular traffic are attracting the
concentration. There is an immediate attention requirement towards the development and
implementation of Ecofriendly pavement construction technologies. Through application of these
technologies the efficient use of existing and waste materials can be made with out creating
problems to the environment and at the same time meeting the quality requirements of the
pavements.
Advances in technology and techniques in the in recent years have made cold recycling an
increasingly popular and cost-effective pavement construction and maintenance technique. It has
been proved in abroad that cold recycling with emulsion or foamed bitumen is one of the best
alternatives to be considered as a rehabilitation option. Cold recycling technology can be an option
which has the potential to address the above mentioned issues.
In the present study an effort is made to study the laboratory and field behaviour of recycled cold
mixes with binders as an emulsion and foamed bitumen. The Marshall specimens were cast using
emulsion and foamed bitumen in combination with different types of fillers such as cement, lime
and fly-ash. The specimens were tested for density, Indirect Tensile Strength, Resilient modulus
and dynamic creep. Benkelman Beam deflection study was carried out on the pavement
constructed with recycled foamed bituminous mix after a period of three months from construction
and field cores were cut from the pavement and were investigated in the Laboratory.
Laboratory and Field Evaluation of Recycled Cold Mixes 2
1.2 Objectives • To study the suitability of cementitious and bituminous agents (Emulsion and Foamed
bitumen) for cold recycling
• To determine optimum content of stabilizing agent
• To study the performance of stabilized mix
1.3 Scope of Work In the present study stabilizing agents viz. cementitious and bituminous was investigated for its
use with Recycled Asphalt Pavement (RAP) material. The effect of different stabilizing agents and
their dosage on density, indirect tensile strength (ITS) and other performance parameters of
stabilized mix were studied.
1.4 Methodology Adopted Determination of foaming properties of bitumen viz. expansion ratio and half life using
Wirtgen WLB 10 foamed bitumen laboratory unit
Preparation of samples using different combinations of granular/RAP material and
stabilizing agents
Preparation of Samples of different combinations of cement, lime, fly-ash, emulsion and
foamed bitumen and testing for density and indirect tensile strength (ITS) to determine
optimum content of stabilizing agent
Determination of Stiffness of bitumen-stabilized material by subjecting 100 mm diameter
Marshall Specimen to repeated load testing
Study of Performance of test track laid with recycled asphalt pavement by evaluating cores
from the existing cold recycled pavement and testing for performance characteristics
Determination of structural adequacy of the Recycled foamed bitumen test track by
Benkelman beam deflection study
Laboratory and Field Evaluation of Recycled Cold Mixes 3
_________________________________________CHAPTER 2
2. LITERATURE REVIEW
2.1 Why Milling? Milling is the process of cutting away material by feeding a work piece past a rotating multiple
tooth cutter. It can be carried out when the pavement condition is in COLD or HOT. Cold milling
is considered to be more economical, ecofriendly in nature and can be done to pavement full
depth.
Earlier roads were designed for less traffic and lighter vehicle weights than found today. Many
roads are being distorted and failing prematurely as a result. Reestablishing a uniform surface is
essential if these roads are to be properly repaired. Milling provides a uniform surface for the
placement of new pavement. If rutted roads are overlaid as it is, insufficient material is placed in
the rutted area, producing low density in the areas of the ruts. By milling to a flat surface, recycled
material is created, the ruts are eliminated, and the new pavement will have a uniform density
across the entire lane. Milling can reestablish the proper road grade and slope and eliminate high
spots and ruts. Many times, milling can reduce or even eliminate reflective cracking. Better
leveling can be achieved by milling than by applying a leveling course of asphalt. Furthermore,
considerable savings result. Other very significant advantages are gained by milling and inlaying
on highway work are Shoulders do not have to be raised, Guard rails do not have to be raised
because the road elevation remains the same. Milling also provides utility accesses (i.e. drain
gullies, man holes, etc) to remain same. Bridge clearances remain the same, so clearance signs do
not have to be changed.
2.2 Why Recycling? Recycling:-The reuse, usually after some processing, of a material that has already served its first
intended purpose.
The reasons for, and advantages from, Recycled Asphalt (RA) being put back in to pavements can
be summarized in the fallowing simple points
• The use of already existing materials, the elimination of disposal problems and
conservation of natural resources (aggregates and petroleum products).
Laboratory and Field Evaluation of Recycled Cold Mixes 4
• Major energy savings, including those related to avoiding processing of additional virgin
material and the potential for reduced haulage of materials with associated reduction in
energy emissions and congestion.
• A cost reduction with respect to other conventional methods of restoring former properties
of the road.
Furthermore, adding RA also provides:
• The opportunity to modify the grading of the aggregate and/or the properties of the binder
in the existing asphalt in order to improve the properties of in-situ mixture.
• The opportunity to correct the profile and/or the cross fall of the pavement and improve the
smoothness and ride quality.[1]
2.3 Methods of Pavement Recycling Pavement may be recycled in-place or in-plant depending on various factors such as availability of
equipment, existing material quality and requirement of the quality control over the treated
material.
An in-situ or in-place recycling process involves a train of machines planing out, and then
immediately processing, the material and relaying it without removing it from site. In-situ
recycling is usually preferred because it is less costly (with the elimination of costs associated the
stockpiling, handling, maintaining an inventory and long distance hauling of the reclaimed
material) and because it causes less disruption to the traffic.
An off-site or in-plant recycling process involves processing the material in a central plant (often
far from the works location) or in a mobile recycling plant just near the works location.
The Asphalt Recycling and Reclaiming Association (ARRA) recognizes five types of asphalt
pavement recycling:
i. Cold planing
ii. Hot recycling
iii. Hot in-place recycling
iv. Cold recycling and
v. Full-Depth Reclamation
Cold planing:- The asphalt pavement is removed to a specified depth and the surface is restored to
a desired grade cross slope and free of humps, ruts and other imperfections. The pavement
Laboratory and Field Evaluation of Recycled Cold Mixes 5
removal or “milling” is completed with a self propelled rotary drum cold planing machine. The
Reclaimed Asphalt Pavement (RAP) is transferred to trucks after removal and stockpiled for hot or
cold recycling.
Hot recycling:-RAP is combined with new aggregate and asphalt cement and/or recycling agent to
produce Hot Mix Asphalt (HMA). Although batch type hot mix plants are used, drum plants
typically are used to produce the recycled mix. Most of the RAP is produced by cold planing but
also can be produced from pavement removal and crushing. The mix placement and compacting
equipment and procedures are those typical of HMA construction.
Hot In-place Recycling (HIPR): The HIPR is defined as a process to correct asphalt pavement
surface distress by softening the existing surface with heat, mechanically removing the pavement
surface, mixing the reclaimed asphalt with a recycling agent, possibly adding virgin asphalt and/or
aggregate, and relaying. A train of machines, working in succession, performs the recycling.
Cold Recycling:- Although cold recycling is performed using a stationary or mobile plant process,
the method most commonly used is Cold In-place Recycling (CIR). For CIR, the existing asphalt
pavement typically is processes to a depth of from 50 to 100mm. the pavement is pulverized and
the reclaimed material is mixed with an Emulsion or foamed bitumen, spread and compacted to
produce a base course. Cold recycled base courses require a new asphalt surface
Full Depth Reclamation (FDR):- With FDR, all of the pavement section, and in some cases a
predetermined amount of underlying material are mixed with asphalt emulsion or Foamed bitumen
to produce a stabilized base course. Base problems can be corrected with this construction. FDR
consists of six basic steps: pulverization, stabilizing agent and/or emulsion or Foamed bitumen
incorporation, spreading, compacting, shaping and placement of new asphalt surface. [2]
2.4 Candidates for Recycling A candidate for recycling is usually an old asphalt pavement, from HMA to an aggregate base
with surface treatment. Candidate pavement will have severe cracking and disintegration, such as
pot holes. Frequently the poor condition is due to the pavement being too thin or weak for the
traffic and so it is being over stressed. Poor drainage can also accelerate the rate and amount of
pavement deterioration. All types of asphalt pavements can be recycled: low, medium and high
traffic volume highways, urban streets, airport taxi ways, runways and aprons, and parking lots.
[2]
Laboratory and Field Evaluation of Recycled Cold Mixes 6
2.5 Advantages of Cold Recycling Cold recycling and full depth reclamation of asphalt pavements provide many environmental and
other advantages:
Energy is conserved as the construction is completed in-place/mobile plant and no fuel is
required for aggregate heating.
Reflective cracking can be controlled since it is normally reduced with CIR and eliminated
by Full Depth Reclamation
Pavement crown and cross slope can be improved or restored.
Pavement maintenance costs can be reduced by increasing Life Cycle Cost of the existing
materials since it is reclaimed.
Traffic can be allowed immediately after construction of the pavement and the obstructions
to the traffic are also nominal since the construction operation can be carried out safely.
Existing material can be used completely (100% usage) irrespective of material quality.
Laboratory and Field Evaluation of Recycled Cold Mixes 7
2.6 Bitumen Emulsion Bitumen emulsions, used in road construction and maintenance, may be defined as a homogeneous
mixture of minute Bitumen droplets suspended in a continuous water phase. These types of
emulsions are usually termed oil-in-water (o/w) emulsions. Emulsions typically contain asphalt
cement, water, and emulsifying agent in the following approximate proportions: 65-70%, 30-35%,
and 2-3%, respectively. Their preparation involves the use of a high speed, high shear mechanical
device, such as a colloid mill. The colloid mill breaks down molten asphalt into minute droplets in
the presence of water and a chemical, surface-active emulsifier. The emulsifier imparts its
properties to the dispersed asphalt arid is most influential in maintaining stable asphalt droplet
suspension.
Advantages of emulsion:
The emulsions are more tolerant than penetration grade bitumens, of the presence of
dampness, although they should not be used in the presence of free water, on the road
surface or on aggregates.
Because emulsions are of relatively low viscous at normal temperatures, they eliminate the
need to heat the aggregates and binder, and thus they conserve energy.
Emulsions use reduces environmental pollution (especially because, unlike cutback
bitumen, they do not release harmful diluents in to the environment).
They can be used when the weather is relatively cold.
Table2. 10: The major uses of bitumen emulsion Surface treatments Asphalt recycling Other applications Fog sealing, Sand sealing, Slurry sealing, Micro-surfacing, Cape sealing
Cold in-place, Full depth, Hot in-place, Central plant
Stabilization, Maintenance patching, Tack coats, Prime coats, Dust palliatives, Crack filling, Protective coatings
Laboratory and Field Evaluation of Recycled Cold Mixes 8
2.7 Bitumen Emulsion Classification Bitumen emulsions are classified into three categories: anionic, cationic and nonionic. In practice
the first two types are more widely used in roadway construction and maintenance.
Emulsions are further classified on the basis of how quickly the bitumen droplets will coalesce.
The terms RS, MS, SS and QS have been adopted in this classification. They are relative terms
only and mean rapid setting, medium setting, slow setting and quick setting. The tendency to
coalesce is closely related to the speed with which an emulsion will become un-stable and break
after contacting the surface of aggregate. An RS emulsion has little or no ability to mix with an
aggregate, an MS emulsion is expected to mix with coarse but not fine aggregate, and SS and QS
emulsions are designed to mix with fine aggregate, with the QS expected to break more quickly
than the SS.
Emulsions are further identified by a series of numbers and letters related to viscosity of the
emulsions and hardness of the base bitumen. The letter “C” in front of the emulsion type denotes
cationic. The absence of “C” denotes anionic in American Society for Testing and Materials
(ASTM) and American Association of State Highway and Transportation Officials (AASHTO)
specifications.
The numbers in the classification indicate the relative viscosity of the emulsion. For example, an
MS-2 is more viscous than an MS-1. The “h” that fallows certain grades simply means that harder
base bitumen is used. An “s” means that softer base bitumen is used.
The “HF” preceding some of the anionic grades indicates high-float, as measured by the float test.
High float emulsions have a gel quality, imparted by the addition of certain chemicals, that permits
a thicker bitumen film on the aggregate particles and prevents drain off of bitumen from the
aggregate. These grades are primarily for cold and hot plant mixes, seal coats and road mixes.[6]
Table2. 11: Bitumen emulsion classification and their recommended application. (IS 8887-2004) Emulsion
type Recommended application
RS-1 Tack coat applications. RS-2 Surface dressing work.
MS Plant or road mixes with coarse aggregates minimum 80%, all of which is retained on 2.36mm IS Sieve, and also for surface dressing and penetration macadam.
SS-1 Fog seal, Crack sealing and Prime coat applications.
SS-2 Plant or road mixes with graded and fine aggregates such as Cold mixes MSS, SDBC and slurry seal.
Laboratory and Field Evaluation of Recycled Cold Mixes 9
2.8 Recycling With Bitumen Emulsion When recycling with bitumen emulsion the following points are important and need to be
addressed:
Mix design
As with any form of stabilisation, a proper mix design procedure should be followed to determine
the correct application rate required to meet the strength criteria. Each material requires its own
application rate of bitumen emulsion to achieve optimum or desired strength.
Formulation
Different emulsifiers and additives are used in varying proportions to “tailor” an emulsion for a
specific application. In addition to determining the amount of residual bitumen suspended in
water, such tailoring is aimed at controlling the conditions under which the bitumen breaks. Since
the type of material that is mixed with the emulsion has a major influence on stability (breaking-
time), it is important that the manufacturer be given a representative sample of the material that is
to be recycled. Details of any active filler to be added in conjunction with the bitumen emulsion
must also be supplied to allow the correct formulation to be developed and tested.
Handling
Bitumen emulsions are susceptible to temperature and pressure. The conditions that will promote
the bitumen to separate out of suspension (slowly as “flocculation”, or instantly as a “flash-break”)
must be clearly understood to prevent this from happening on the site. Likewise, the manufacturer
must know the conditions prevailing on site to allow the correct formulation, including the details
of all pumps that will be used for transferring the emulsion between tankers and for supplying the
spray bar on the recycler. Blending of anionic and cationic emulsions results in an instantaneous
break and blockage of pumps and pipes with viscous bitumen, for example. This can be prevented
by labeling and storing emulsions carefully and ensuring that distribution systems are clear of
residue from previous use.
Total fluid content concept
When working with bitumen emulsions, “Total Fluid Content” is used in place of Moisture
Content in defining the moisture/density relationship. Maximum density is achieved at the
Optimum Total Fluid Content (OTFC), which is the combined mass of moisture and bitumen
emulsion in the mix. Before breaking, bitumen emulsion is a fluid with a viscosity slightly higher
Laboratory and Field Evaluation of Recycled Cold Mixes 10
than that of water. Both the bitumen and water components of an emulsion act as a lubricant in
assisting compaction, so both must be included as fluids. This is illustrated in Figure 2-1.
Figure 2-1 Example of fluid considerations for a bitumen emulsion stabilised material
The example in Figure 2-1 shows the in-situ field moisture content as 2.5 % with 3.5 % bitumen
emulsion applied whilst recycling. The material has an OTFC of 7% under standard compaction.
An additional 1.0% of water may be added during recycling to bring the total fluid content to the
OTFC, or additional compactive effort applied to achieve maximum density. If the total fluid
content of the material approaches saturation level (as indicated by the zero air voids line), then
hydraulic pressures will develop under the roller causing the material to heave. When such
conditions arise it is impossible to compact the material. Where the in-situ field moisture content
is high (i.e. approaching the OTFC), the addition of bitumen emulsion can increase the total fluid
content beyond the saturation point. This situation cannot be addressed by reducing the amount of
bitumen emulsion added without compromising the quality of the stabilised product. The
temptation to add cement to the mix in order to “absorb the surplus moisture” should not be
considered since such a practice introduces rigidity and changes the nature of the product. High in-
Laboratory and Field Evaluation of Recycled Cold Mixes 11
situ moisture contents are best addressed by pre-pulverising the existing pavement thereby
exposing the material and allowing it to dry sufficiently before stabilising.
Processing time
No specific time limit is placed on working with bitumen emulsions other than the requirement of
completing all processing, compacting and finishing before the emulsion breaks. When emulsion
breaks, the bitumen comes out of suspension and the viscosity of the fluid increases significantly.
The individual particles of the recycled material will then be either coated, or semi-coated with a
thin film of cold, viscous bitumen, making it more difficult to compact. Compaction should
therefore be completed before or during the emulsion breaking process.
Density
The compaction should always aim to achieve the maximum density possible under the conditions
prevailing on site (the so-called “refusal density”). A minimum density is usually specified as a
percentage of the modified AASHTO density, normally between 98 and 102% for bitumen
stabilised bases.
Quality control
Briquettes (for strength testing) are normally manufactured from samples taken immediately
behind the recycler. These briquettes must be made before the emulsion breaks, thereby obtaining
specimens that reflect the compacted material on the road. Often the only way that this can be
achieved is by having a mobile compaction facility on site to manufacture the briquettes.
Alternatively, cores can be extracted at a later date once the layer has fully cured.
Curing
In order to gain strength, an emulsion mix must dispel excess water, or cure. Although some
materials stabilised with bitumen emulsion may achieve their full strength within a short period of
time (one month), curing can take longer than a year with other materials. The length of this
period is affected by field moisture content, emulsion/aggregate interaction, local climate
(temperature, precipitation and humidity) and voids in the mix. Cement addition has a significant
impact on the rate of gain of strength. This is particularly useful where traffic is to be
accommodated on a recycled layer shortly after treatment, Research, however, has shown that
adding more than 2% by mass negatively affects the fatigue properties of the stabilised layer. For
this reason the application rate of cement is usually limited to preferably 1.5% maximum but an
absolute maximum of 2%.
Laboratory and Field Evaluation of Recycled Cold Mixes 12
2.9 Foamed Bitumen In order to mix bitumen with road-building aggregates, you first need to considerably reduce the
viscosity of the cold hard binder. Traditionally, this was done by heating the bitumen and mixing
it with heated aggregates to produce hot mix asphalt. Other methods of reducing the bitumen
viscosity include dissolving the bitumen in solvents and emulsification. Prof. Csanyi came up
with the idea of introducing moisture into a stream of hot bitumen, which effects a spontaneous
foaming of the bitumen (similar to spilling water into hot oil). The potential of foamed bitumen for
use as a binder was first realised in 1956 by Dr. Ladis H. Csanyi, at the Engineering Experiment
Station in Iowa State University. Since then, foamed asphalt technology has been used
successfully in many countries, with corresponding evolution of the original bitumen foaming
process as experience was gained in its use. The original process consisted of injecting steam into
hot bitumen. The steam foaming system was very convenient for asphalt plants where steam was
readily available but it proved to be impractical for in situ foaming operations, because of the need
for special equipment such as steam boilers. In 1968, Mobil Oil Australia, which had acquired the
patent rights for Csanyi’s invention, modified the original process by adding cold water rather than
steam into the hot bitumen. The bitumen foaming process thus became much more practical and
economical for general use.[4]
Figure 2-2 schematic diagram of foamed bitumen production
The foamed bitumen, or expanded bitumen, is produced by a process in which pressurized water
and compressed air is injected into the hot bitumen (155-180 0c), resulting in spontaneous
foaming. The physical properties of the bitumen are temporarily altered when the injected water,
Laboratory and Field Evaluation of Recycled Cold Mixes 13
on contact with the hot bitumen, is turned into vapour which is trapped in thousands of tiny
bitumen bubbles. In the foam state the bitumen has a very large surface area and extremely low
viscosity making it ideal for mixing with aggregates however the foam dissipates in less than a
minute and the bitumen resumes its original properties. In order to produce foamed asphalt mix,
the bitumen has to be incorporated into the aggregates while still in its foamed state. A distinct
difference between foamed asphalt mixes and conventional asphalt stabilised mixes is the way in
which the bitumen is dispersed through the aggregate. In the later case the bitumen tends to coat
all particles whilst in the foamed mixes the larger particles are not fully coated. The foamed
bitumen disperses itself among the finer particles forming a mortar which binds the mix together.
Foamed bitumen mixes can achieve stiffness close to those of cement treated bases (3000 MPa)
but remains flexible like asphalt mix.[5]
2.10 Characterization of Foamed Bitumen Foamed bitumen is characterized by two primary properties:
1. Expansion Ratio that is a measure of the viscosity of the foam and will determine how
well it will disperse in the mix. It is calculated as the ratio of the maximum volume of
foam relative to its original volume or
Foam ratio, it is calculated as the maximum expanded volume of bitumen foam to its
weight and
2. Half-Life is a measure of the stability of the foam and provides an indication of the rate of
collapse of the foam. It is calculated as the time taken in seconds for the foam to collapse
to half of its maximum volume.
The “best” foam is generally considered to be the one that optimizes both expansion and half-life.
Laboratory and Field Evaluation of Recycled Cold Mixes 14
Figure 2-3: Bitumen Foam characterization
2.11 Factors influencing foam properties The expansion ratio and half-life of foamed bitumen is influenced by:
Water addition: Increasing the amount of water injected into the bitumen effectively increases the
volume of foam produced by a 1500 times multiplier. Thus, increasing the amount of water
increases the size of the bubbles created, causing the expansion ratio to increase. However,
increasing the size of the individual bubbles reduces the film thickness of the surrounding
bitumen, making it less stable and resulting in a reduction in half-life. Hence, the expansion ratio
and half-life are inversely related to the amount of water that is added,
Bitumen type: Bitumens with penetration values between 80 and 150 are generally used for
foaming, although harder bitumens that meet the minimum foaming requirements (explained
below) have been successfully used in the past. For practical reasons, harder bitumens are
generally avoided as they produce poorer quality foam, leading to poorer dispersion.
Laboratory and Field Evaluation of Recycled Cold Mixes 15
Bitumen source: Some bitumens foam better than others due to their composition. For example,
the foaming properties of bitumens from Venezuela far exceed those from most other sources.
Bitumen temperature: The viscosity of bitumen enjoys an inverse relationship with temperature;
as the temperature increases, its viscosity reduces. Logically, the lower the viscosity, the bigger
the size of bubble that will form when the water changes state in the foaming process. Since this
process draws heat energy from the bitumen, the temperature before foaming needs to exceed 160
ºC to achieve a satisfactory product.
Bitumen and water pressure: Bitumen and water are injected into the expansion chamber through
small diameter openings. Increasing the pressure in the supply lines causes the flow through these
openings to disperse (atomize). The smaller the individual particles, the larger the contact area
available, thereby improving the uniformity of the foam;
Additives: There are numerous proprietary products on the market that will affect the foaming
properties of bitumen, both negatively (anti-foaming agents) and positively (foamants). Foamants
are usually only required where bitumen has been treated with an anti-foaming agent (normally
during refining process). Most foamants are added to the bitumen prior to heating to application
temperatures and tend to be heat-sensitive; implying that their effect is short lived. To reap the
benefits of adding a foamant, the bitumen must therefore be used within a few hours. However,
these products are generally expensive and are usually only considered as a last resort to
improving the foaming properties of stubborn bitumen. (Cutting back the bitumen with diesel oil
has proved successful in reducing the viscosity of the bitumen sufficiently to achieve acceptable
foam. However, this is not recommended unless carried out by the bitumen supplier.)
Acceptable foaming characteristics
The bitumen intended to be used for foaming should be tested in the laboratory to determine the
foaming characteristics. The objective of this exercise is to find that combination of water addition
and bitumen temperature at which the optimal foam (highest Expansion Ratio and Half-Life) is
achieved. As described above, every bitumen is different and even different batches of bitumen
from the same source will vary. However, by following the simple laboratory procedure, the water
application and bitumen temperature is determined for each bitumen and these are then used on
site for full-scale foamed bitumen stabilisation. There are no upper limits to foaming
characteristics and the aim should always be to produce the best quality foam for stabilisation.
Problems are only encountered when a bitumen fails to produce a “good” foam, necessitating that
Laboratory and Field Evaluation of Recycled Cold Mixes 16
lower limits be recognized. Normally accepted minimum values for expansion ratio and half-life
for stabilising material at 25 ºC are:
Expansion Ratio 10 times and Half-Life 8 seconds.
Experience has shown that adequate foam dispersion and effective stabilisation is possible
when the expansion ratio is as low as 8 times and the half-life is only 6 seconds. However,
factors other than the foaming characteristics are often responsible, such as elevated material
temperatures. During his research into foamed bitumen during the late 1990s, Prof. Jenkins
developed the concept of a “Foam Index” to measure the combination of expansion ratio and half-
life. He defined this Foam Index as the area under the curve obtained by plotting Expansion Ratio
against Half-life, concluding that the better the foaming properties, the greater the Foam Index and
the better the stabilised product achieved. His research went on to compare the effect of Foam
Index with the temperature of the material at the time of mixing, concluding that as the
temperature of material increases, a lower Foam Index can be used to achieve effective
stabilization.[7]
2.12 Dispersion of foamed bitumen Unlike hot-mix asphalt, material stabilised with foamed bitumen does not appear black. This
results from the coarser particles of aggregate not being coated with bitumen. When foamed
bitumen comes into contact with aggregate, the bitumen bubbles burst into millions of tiny
bitumen droplets that seek out and adhere to the fine particles, specifically the fraction smaller
than 0.075 mm. The bitumen droplets can exchange heat only with the filler fraction and still have
sufficiently low viscosity to coat the particles. The foamed mix results in a bitumen-bound filler
that acts as a mortar between the coarse particles, as shown previously in Figure 4.1. There is
therefore only a slight darkening in the color of the material after treatment. The addition of
cement, lime or other such fine cementitious material (100 % passing the 0.075 mm sieve) assists
the bitumen to disperse, in particular where the recycled material is deficient in fines.
Laboratory and Field Evaluation of Recycled Cold Mixes 17
Figure 2-4: Foamed bitumen dispersion and binding in the treated mix
2.13 Material suitability for foamed bitumen treatment The foamed bitumen process is suitable for treating a wide range of materials, ranging from sands,
through weathered gravels to crushed stone and RAP. Aggregates of sound and marginal quality,
from both virgin and recycled sources have been successfully utilized in the process in the past. It
is important, however, to establish the boundaries of aggregate acceptability, as well as to identify
the optimal aggregate composition for foamed bitumen mix production. Material that is deficient
in fines will not mix well with foamed bitumen. As depicted in Figure 4.11, the minimum
requirement is 5% passing the 0.075 mm (No. 200) sieve. When a material has insufficient fines,
the foamed bitumen does not disperse properly and tends to form what are known as “stringers”
(bitumen rich agglomerations of fine material) throughout the recycled material. These stringers
vary in size according to the fines deficiency, a large deficiency will result in many large stringers
which will tend to act as a lubricant in the mix and lead to a reduction in strength and stability.
Laboratory and Field Evaluation of Recycled Cold Mixes 18
Figure 2-5: Material gradation envelops
Simple laboratory gradation tests carried out on representative samples taken from the existing
road will indicate any potential deficiency in the fines content. This can be rectified by importing a
suitable fine material and spreading on the road surface prior to recycling. Cohesive materials
should, however, be treated with care as standard laboratory gradings will indicate a high
percentage passing the 0.075 mm sieve, whilst in the field the quality of mixing is often poor. This
is due to the cohesive nature of the material causing the fines to bind together, thereby making
them unavailable to disperse the foamed bitumen. Comparison of washed and unwashed grading
tests carried out in the laboratory will indicate the likelihood of this problem developing, the
unwashed grading giving an indication of the available fines. Material that is deficient in fines can
be improved by the addition of cement, lime or other such material with 100 % passing the 0.075
mm sieve. However, the use of cement in excess of 1.5 % by mass should be avoided due to the
negative effect on the flexibility of the stabilised layer. The envelopes provided in Figure 2.5 are
broad and can be refined by targeting a grading that provides the lowest voids in the mineral
aggregate. This produces foamed bitumen mixes with the most desirable mix properties. A unique
relationship for achieving the minimum voids, with an allowance for variation in the filler content,
is shown in equation. This relationship is useful as it provides flexibility with the filler content of a
mixture. A value of n = 0.45 is utilised to achieve the minimum voids.
Where: d = selected sieve size (mm)
Laboratory and Field Evaluation of Recycled Cold Mixes 19
P = percentage by mass passing a sieve of size d (mm)
D = maximum aggregate size (mm)
F = percentage filler content (inert and active)
n = variable dependent on aggregate packing characteristics (0.45)
Achieving a continuous grading on the fraction less than 2 mm is important for the proper
dispersion of the foamed bitumen and easier compaction, thereby reducing voids and the
material’s susceptibility to water ingress. Where necessary, therefore, consideration should be
given to blending two materials to improve the critical grading characteristics.
2.14 Recycling with foamed bitumen Points to be considered while treating with Foamed bitumen Material temperature
Aggregate temperature is one of the primary factors influencing the successful dispersion of
foamed bitumen and, consequently, the strength achieved in the new pavement layer. As
mentioned above, the Foam Index concept developed by Prof. Jenkins represents the combined
foaming properties of bitumen (expansion ratio and half-life). His research finding showed that the
Foam Index and aggregate temperature (at the time of mixing) were important factors in the
dispersion achieved. Higher Foam Indices (i.e. better expansion and half-life) are necessary for
achieving a satisfactory mix at lower temperatures. Although the implications of these findings are
significant, it is important to compare laboratory conditions to those encountered in the field. The
quality of foam produced by a laboratory unit is always inferior to that produced by a large
recycler, the major reasons being higher working pressures in the field and continuity of operation
allowing the system to function at higher temperatures. There is therefore a shift between
laboratory and field measurements and, for this reason, it is important to check the foaming
properties in the field. These measurements should then be compared with the temperature of the
aggregate (not the road surface) and the results checked with the guidelines in Table. When the
temperature of the aggregate drops below 10 °C, foamed bitumen treatment should not be
considered.
Laboratory and Field Evaluation of Recycled Cold Mixes 20
Table2. 12: Foamed bitumen dispersion (ability to mix)
Consistency of bitumen supply
When coupling a new tanker to the recycler, two basic checks should be conducted to ensure that
the bitumen is acceptable for foaming:
– The temperature of the bitumen in the tanker should be checked using a calibrated thermometer
(gauges fitted to tankers are notoriously unreliable); and
– The foaming quality should be checked using the test nozzle on the recycler. This check should
be delayed until at least 100 liters of bitumen has passed through the spraybar whilst recycling in
order to obtain a truly representative sample.
Bitumen flow
Bitumen delivered to site by tankers that are fitted with fire-heated flues is sometimes
contaminated with small pieces of carbon that form on the sides of the flues whilst heating.
Draining the last few tons from the tanker tends to draw these unwanted particles into the
recycler’s system and can cause blockages. This problem is easily resolved by ensuring the
effectiveness of the filter in the delivery line. Any unusual increase in pressure will indicate that
the filter requires cleaning, a procedure that should anyway be undertaken on a regular basis (e.g.
at the end of every shift).
Bitumen pressure
The quality of foam is a function of bitumen operating pressure. The higher the pressure, the more
the stream of bitumen will tend to “atomise” as it passes through the jet into the expansion
chamber. This ensures that small bitumen particles will come in contact with the water that
similarly enters the expansion chamber in an atomised form, thereby promoting uniformity of
foam. If the bitumen were to enter the expansion chamber as a stream (as it does under low
pressures) the water would impact on only one side of the stream, creating foam, but the other side
would remain as unfoamed hot bitumen. It is therefore imperative to maintain a minimum
operating pressure above 3 bars.
Laboratory and Field Evaluation of Recycled Cold Mixes 21
Application of active filler
As described above, it is standard practice to add a small amount of cement or other such
cementitious stabilising agent when recycling with foamed bitumen. Care should be taken when
pre-treating with cement since the hydration process commences as soon as the dry powder comes
into contact with moisture, binding the fines and effectively reducing the 0.075 mm fraction. The
quality of the mix when foamed bitumen is subsequently added will be poor due to insufficient
fines being available to disperse the bitumen particles. Cement should therefore always be added
in conjunction with the foamed bitumen.
Table2. 13: Typical foamed bitumen contents relative to key aggregate fractions Percent passing
4.75 mm 0.075 mm Foamed bitumen content, %
3 – 5 3
5 – 7.5 3.5
7.5 – 10 4 < 50 (Gravel)
> 10 4.5
3 – 5 3.5
5 – 7.5 4
7.5 – 10 4.5 > 50 (Sands)
> 10 5
Table2. 14: Tentative binder and additional treatment requirements Material type
Optimum range of
binder
Additional requirements
Well graded clean gravel 2 to 2.5%
Well graded marginally clayey/silty
gravel
2 to 4.5%
Poorly graded marginally clayey gravel 2.5 to 3%
Clayey gravel 4 to 6% Lime modification
Well graded clean sand 4 to 5% Filler
Well graded marginally silty sand 2.5 to 4%
Poorly graded marginally silty sand 3 to 4.5% Low penetration bitumen,
Laboratory and Field Evaluation of Recycled Cold Mixes 22
filler
Poorly graded clean sand 2.5 to 5% filler
Silty sand 2.5 to 4.5%
Silty clayey sand 4% Possibly lime
Clayey sand 3 to 4% Lime modification
Moisture Conditions The moisture content during mixing and compaction is considered by many researchers to be the
most important mix design criteria for foamed asphalt mixes. Moisture is required to soften and
breakdown agglomerations in the aggregates, to aid in bitumen dispersion during mixing and for
field compaction. Insufficient water reduces the workability of the mix and results in inadequate
dispersion of the binder, while too much water lengthens the curing time, reduces the strength and
density of the compacted mix and may reduce the coating of the aggregates. The optimum
moisture content (OMC) varies, depending on the mix property that is being optimized (strength,
density, water absorption, swelling). However, since moisture is critical for mixing and
compaction, these operations should be considered when optimizing the moisture content.
Investigations by Mobil Oil suggest that the optimum moisture content for mixing lies at the “fluff
point” of the aggregate, i.e. the moisture content at which the aggregates have a maximum loose
bulk volume (70 % - 80 % mod AASHTO OMC) . However, the fluff point may be too low to
ensure adequate mixing (foam dispersion) and compaction, especially for finer materials. The
optimum mixing moisture content occurs in the range of 65 - 85 per cent of the modified
AASHTO OMC for the aggregates. The concept of optimum fluid content as used in granular
emulsion mixes may also be relevant to foamed asphalt. This concept considers the lubricating
action of the binder in addition to that of the moisture. Thus the actual moisture content of the mix
for optimum compaction is reduced in proportion to the amount of binder incorporated. The best
compactive moisture condition occurs when the total fluid content (moisture + bitumen) is
approximately equal to the OMC. [4]
Processing time No specific time limit is placed on working with foamed bitumen. Provided the moisture content
of the material is maintained close to the optimum moisture content, the working period can be
extended.
Curing Conditions
Laboratory and Field Evaluation of Recycled Cold Mixes 23
Studies have shown that foamed asphalt mixes do not develop their full strength after compaction
until a large percentage of the mixing moisture is lost. This process is termed curing. Curing is the
process whereby the foamed asphalt gradually gains strength over time accompanied by a
reduction in the moisture content. A laboratory mix design procedure would need to simulate the
field curing process in order to correlate the properties of laboratory- prepared mixes with those of
field mixes. Since the curing of foamed asphalt mixes in the field occurs over several months, it is
impractical to reproduce actual field curing conditions in the laboratory. An accelerated laboratory
curing procedure is required, in which the strength gain characteristics can be correlated with field
behaviour, especially with the early, intermediate and ultimate strengths attained. This
characterization is especially important and required when structural capacity analysis is based on
laboratory-measured strength values. Most of the previous investigations have adopted the
laboratory curing procedure proposed by Bowering (1970), i.e. 3 days oven curing at a temperature
of 60° C. This procedure results in the moisture content stabilizing at about 0 to 4 per cent, which
represents the driest state achievable in the field. In the present study the specimen are cured for 72
hours at 40 0C temperature only.
Density Generally density increases to a maximum and decreases as the binder content of a foamed asphalt
mix increases. The strength of foamed asphalt mixes depends to a large extent on the density of
the compacted mix. Compaction should always aim to achieve the maximum density possible
under the conditions prevailing on site (the so-called “refusal density”). A minimum density is
usually specified as a percentage of the modified AASHTO density, normally between 98 % and
102 % for foamed bitumen stabilised bases. A density gradient is sometimes permitted by
specifying an “average” density. This means that the density at the top of the layer may be higher
than at the bottom. Where specified, it is normal also to include a maximum deviation of 2% for
the density measured in the lowest one-third thickness of the layer. Hence, if the average density
specified is 100%, then the density at the bottom of the layer must be more then 98 %. For better
quality aggregates (e.g. CBR > 80 %) it is advisable to use an absolute density specification such
as Bulk Relative Density or Apparent Relative Density of the aggregate.
Engineering Properties The results of previous studies all confirm that strength parameters such as Resilient Modulus,
CBR and stability are optimized at a particular intermediate binder content. The most common
method used in the selection of the design binder content was to optimize the Marshall stability and
Laboratory and Field Evaluation of Recycled Cold Mixes 24
minimize the loss in stability under soaked moisture conditions. The major functions of foamed
bitumen treatment are to reduce the moisture susceptibility, to increase fatigue resistance and to
increase the cohesion of the untreated aggregate to acceptable levels. The design foamed bitumen
content could also be selected as the minimum (not necessarily optimum) amount of binder which
would result in a suitable mix.
Moisture Susceptibility
The strength characteristics of foamed asphalt mixes are highly moisture-dependent at low binder
contents. Additives such as lime or Cement reduced the moisture susceptibility of the mixes.
Higher bitumen contents also reduce moisture susceptibility because higher densities are
achievable, leading to lower permeabilities (lower void contents), and to increased coating of the
moisture-sensitive fines with binder. The moisture susceptibility of the material is usually
determined in terms of the Tensile Strength Retained (TSR) by 100 mm briquettes, using below
equation.
Temperature Susceptibility
Foamed asphalt mixes are not as temperature-susceptible as hot-mix asphalt, although both the
tensile strength and modulus of the former decrease with increasing temperature. Bissada (1987)
found that, at temperatures above 30° C, foamed asphalt mixes had higher moduli than equivalent
hot-mix asphalt mixes after 21 days’ curing at ambient temperatures. In foamed asphalt, since the
larger aggregates are not coated with binder, the friction between the aggregates is maintained at
higher temperatures. However the stability and viscosity of the bitumen-fines mortar will decrease
at high temperatures, thus accounting for the loss in strength.
Unconfined Compressive Strength (UCS) and Tensile Strength
Bowering (1970) suggested the following UCS criteria for foamed asphalt mixes used as a base
courses under thin surface treatments (seals): 0.5 MPa (4 day soaked) and 0.7 MPa (3 day cured at
60° C). Bowering and Martin (1976) suggested that in practice the UCS of foamed asphalt
materials usually lie in the range 1.8 MPa to 5.4 MPa and estimated that the tensile strengths of
foamed asphalt materials lay in the range 0.2 MPa to 0.55 MPa, depending on moisture condition.
Laboratory and Field Evaluation of Recycled Cold Mixes 25
Bitumen stabilised material is normally evaluated using the Indirect Tensile Strength (ITS) in
preference to Marshall testing with the fallowing advantages.
Simple to conduct the test
Specimen and the equipment are the same as those used for a Marshall testing machine.
The coefficient of variation of the test results is low as compared to other test methods and
This can be used to test under a static load i.e. a single load till failure.
For good performance, cured foamed asphalt samples should have minimum Indirect Tensile
Strengths of 100 kPa when tested in a soaked state and 200 kPa when tested dry.
Stiffness - Resilient Modulus
As with all viscoelastic bituminous materials, the stiffness of foamed asphalt depends on the
loading rate, stress level and temperature. Generally, stiffness has been shown to increase as the
fines content increases. In many cases the resilient moduli of foamed asphalt mixes have been
shown to be superior to those of equivalent hot-mix asphalt mixes at high temperatures (above 30°
C). Foamed asphalt can achieve stiffnesses comparable to those of cement-treated materials, with
the added advantages of flexibility and fatigue resistance.
Abrasion Resistance
Foamed asphalt mixes usually lack resistance to abrasion and ravelling and are not suitable for
wearing/friction course applications.
Fatigue Resistance
Fatigue resistance is an important factor in determining the structural capacity of foamed asphalt
pavement layers. Foamed asphalt mixes have mechanical characteristics that fall between those of
a granular structure and those of a cemented structure. Bissada (1987) considers that the fatigue
characteristics of foamed asphalt will thus be inferior to those of hot-mix asphalt materials. Little et
al (1983) provided evidence of this when he showed that certain foamed asphalt mixes exhibited
fatigue responses inferior to those of conventional hot-mix asphalt or high quality granular
emulsion mixes.
Laboratory and Field Evaluation of Recycled Cold Mixes 26
2.15 The benefits of foamed bitumen stabilisation
The following advantages of foamed asphalt are well documented:
• The foamed binder increases the shear strength and reduces the moisture susceptibility of
granular materials. The strength characteristics of foamed asphalt approach those of
cemented materials, but foamed asphalt is flexible and fatigue resistant.
• Foam treatment can be used with a wider range of aggregate types than other cold mix
processes.
• Reduced binder and transportation costs, as foamed asphalt requires less binder and water
than other types of cold mixing.
• Saving in time, because foamed asphalt can be compacted immediately and can carry
traffic almost immediately after compaction is completed.
• Energy conservation, because only the bitumen needs to be heated while the aggregates are
mixed in while cold and damp (no need for drying).
• Environmental side-effects resulting from the evaporation of volatiles from the mix are
avoided since curing does not result in the release of volatiles.
• Foamed asphalt can be stockpiled with no risk of binder runoff or leeching. Since foamed
asphalt remains workable for much extended periods, the usual time constraints for
achieving compaction, shaping and finishing of the layer are avoided.
• Foamed asphalt layers can be constructed even in some adverse weather conditions, such
as in cold weather or light rain, without significantly affecting the workability or the
quality of the finished layer.
The limitations are:
• Requires a suitable grading of fines in the pavement material
• Purpose built equipment and experienced operators are required
• A relative lack of abrasion resistance at surface and requires consideration of a good
surface course over the foamed bitumen treated layer.
Where would we consider this rehabilitation option?
This effective pavement rehabilitation option may be considered in most situations, such as:
• A pavement has been repeatedly patched to the extent that pavement repairs are no longer
cost effective;
Laboratory and Field Evaluation of Recycled Cold Mixes 27
• A weak granular base overlies a reasonably strong subgrade.
• A granular base too thin to consider using cementitious binders
• Conventional reseals or thin asphalt overlays can no longer correct flushing problems.
• An alternative to full-depth asphalt in moderate to high trafficked roads.
• Unfavorable wet cyclic conditions unsuitable for granular construction.
• Situations where an overlay is not possible due to site constraints e.g. entries to adjacent
properties & flood prone areas
• A requirement to complete the rehabilitation quickly to prevent disruption to business or
residents
Laboratory and Field Evaluation of Recycled Cold Mixes 28
Table2.15: Comparison between different types of bitumen applications Factor Bitumen Emulsion Foamed Bitumen Hot Mix Asphalt
Aggregate types
applicable
Crushed rock
Natural gravel
RAP, Cold mix
RAP, stabilised
Crushed rock
Natural gravel
RAP, stabilised
Marginal (Sands)
Crushed rock
0 to 50% RAP
Bitumen Mixing
Temperature
20 0C to 70 0C 160 0C to 180 0C
(Before foaming)
140 0C to 180 0C
Aggregate
temperature during
mixing
Ambient (cold) Ambient (cold) Hot only
(140 0C to 200 0C)
Moisture content
during mixing
90% of OMC minus
50% of emulsion
content
Below OMC
(e.g 65% to 95% of
OMC)
Dry
Type of coating of
aggregate
Partial coating of
coarse particles and
cohesion of mix with
bitumen / fines mortar
Coating of fine
particles only with
“spot welding” of mix
from the bitumen /
fines mortar
Coating of all
aggregate particles
with controlled film
thickness
Construction and
compaction
temperature
Ambient Ambient 140 0C to 160 0C
Rate of initial strength
gain
Slow Medium Fast
Modification of
binder
Yes Unsuitable Yes
Important parameters
of binder
Emulsion type
Residual bitumen
Breaking time
Curing
Half life
Expansion ratio
Penetration
Softening point
Viscosity
Laboratory and Field Evaluation of Recycled Cold Mixes 29
2.16 Case studies
Experience in India:
2.16.1 Emulsion Cold Recycling Rehabilitation Project-Hyderabad Project location Toli chowki area, Hydrabad
The road connecting Rethibowli and Gachibowli. The traffic made
up of cars, light vans, city buses and large delivery trucks.
Recycling method The rehabilitation method chosen for this road was Cold In Place
Recycling using an Emulsion as the binding agent. The Cold In-
Place Recycling option was chosen for the following reasons:
• Lower cost
• Ability to keep road open to business traffic
• Speed of operation
Road details Width of the road: 14m
Length of the road: 400m
Depth of the recycled layer: 120mm
Material composition RAP: 91%
Fine aggregate (P-2.36mm): 4%
Cement: 2%
Bitumen Emulsion: 3%;
Construction:
• Initially calculated amount of 2% of cement by weight of recycled mix was placed over the
road to be recycled. Later around 2% of fine aggregate passing 2.36mm was uniformly
spread over the section.
• With the help of recycler along with emulsion tanker the recycling job was carried out after
milling to a depth of 120mm of the existing surface while simultaneously mixing the
cement, emulsion (@ 3%), water and milled material to form a homogeneous mixture.
• The recycler is equipped with tamping screed, relayed the recycled material and at the
same time pre-compacted it.
Laboratory and Field Evaluation of Recycled Cold Mixes 30
• The laid recycled layer was compacted with a 15tonne vibratory roller. Initially high
amplitude and low frequency mode was selected and later after few passes the mode was
changed to low amplitude and high frequency so as to ensure proper compaction
throughout the recycled thickness.
• Next to rolling with the vibratory roller, a pneumatic tyred roller was used to complete the
final process of compaction.
• After one day water was sprinkled over the laid surface to enable proper curing.
• Later the road was opened to the traffic. However it was felt appropriate to provide a layer
of tack coat followed by a surface course of SDBC.
Laboratory and Field Evaluation of Recycled Cold Mixes 31
Figure2.6: A view of recycling process progress in Hyderabad
Figure2.7: Aggregate Spread over the layer to be recycled to correct the Gradation
Laboratory and Field Evaluation of Recycled Cold Mixes 32
Figure2.8: Recycling crew in action
Figure2.9: Recycled layer after pre-compaction
Laboratory and Field Evaluation of Recycled Cold Mixes 33
Figure2.10: Compacting the recycled layer
Figure2.11: Tack coat application over the recycled and compacted layer
Laboratory and Field Evaluation of Recycled Cold Mixes 34
Figure2.12: Finished surface of the recycled layer
Laboratory and Field Evaluation of Recycled Cold Mixes 35
2.16.2 Foam bitumen cold recycling rehabilitation project-Bangalore Existing Pavement
Kumbalgodu is an Industrial area, traffic made up of cars, light
vans and large delivery trucks. The road is 5m wide and average
asphalt thickness of 20mm.
Recycling Method In-Plant Cold Recycling
Project location Kumbalgodu industrial area phase-I, Bangalore.
A street road connecting state highway No:17 (Bangalore-Mysore)
and some industries (Pressman India Pvt. Ltd, Karnataka cold
storage Pvt. Ltd. etc.)
Road details Width of the road: 5m
Length of the road: 400m
Depth of the Recycled layer: 100mm
Material sourced from RAP material from BC layer of SH-17 from 31 km to 33 km.
Crusher Stone Dust from BIDADI village quarry located at
35+100 km of SH-17.
Bitumen used for foaming is of 80/100 penetration grade.
Material composition RAP: 75% by wt of aggregate;
Stone Dust: 25% by wt of aggregate
Cement: 1.5% by wt of aggregate;
Foamed bitumen: 3.5% by wt of mix;
Water: 3% by wt of mix
Construction:
• The road to be paved with plant recycled material was cleaned and sprinkled with water to
damp the surface to ensure proper bond.
• Foamed bituminous recycled mix was prepared in the mobile mixing plant (KMA-200)
using RAP, Stone dust, Cement and Foamed bitumen in formulated proportions just near
by the working site.
• Recycled plant mix was transported by dumper and is dumped in to the hopper of the paver
to lay the foamix.
Laboratory and Field Evaluation of Recycled Cold Mixes 36
• The compaction process was started with vibratory roller and is finished with pneumatic
tyred roller to achieve specified density and smooth finished surface.
• The recycled road surface was opened to the traffic after 12 hours of construction.
• Two coats of tack coat application and dust spreading was being carried out to seal the
surface in a gap of 4 days.
Laboratory and Field Evaluation of Recycled Cold Mixes 37
Figure2.13: Loader used to load the materials in to the mobile plant
Figure2.14: Cement and hot bitumen supplied to the plant
Laboratory and Field Evaluation of Recycled Cold Mixes 38
Figure2.15: Recycled material being discharged in to the dumper
Figure2.16: Recycled foamix being dumped in to the paver hopper
Laboratory and Field Evaluation of Recycled Cold Mixes 39
Figure2.17: Initial compaction with vibratory roller
Figure2.18: Final compaction with pneumatic tyred roller
Laboratory and Field Evaluation of Recycled Cold Mixes 40
Experience in abroad:
2.16.3 Emulsion Cold Recycling Rehabilitation Project. Citizen Court, Toronto, June 2003 Existing Pavement
Citizen Court is an Industrial area, traffic made up of cars, light
vans and large delivery trucks (Container type). The road is
10.4m wide with and average asphalt thickness of 90mm. The
existing pavement is 18 years old and has reached the end of it’s
useful life, distress is mainly localised base failure with alligator
cracking.
Rehabilitation Method:
The rehabilitation method chosen for Citizen Court was Cold In
Place Recycling using an Emulsion as the binding agent. The
Cold In-Place Recycling option was chosen for the following
reasons:
• Lower cost
• Ability to keep road open to business traffic
• Speed of operation
Design Mix:
Depth of cutting 80 mm
Grindings 98.40%
Emulsion 1.60%
Water Added 2.90% and
Finish Course 40 mm Asphalt concrete
Recycling Train The Recycling train consisted: Wirtgen 2200CR (fitted 2.5m
width milling drum), Emulsion Supply tanker. The Emulsion
Tanker is pushed by the Wirtgen 2200CR, the recycler therefore
controls the speed of operation, and the emulsion application rate
is proportional to recycler forward speed (Average speed 7.5m /
min.). The water for compaction is drawn from the 2200CR
onboard water tank, 5000 litre capacity. The Compaction
achieved using: Single steel drum vibratory compactor, followed
by Pneumatic Multi Tyred Compactor.
Laboratory and Field Evaluation of Recycled Cold Mixes 41
Recycling Sequence of Operation
Pass No 1:
2.5m wide, from centre line out. The total width of the pavement was 10.4m wide, 5.2m half
width. Maximum recycled width with 2 passes of the 2200CR (fitted with 2.5m cutter) was 4.9m,
allowing overlap of 0.1 m at the joint. Therefore, it was necessary to mill 0.5m width x 80mm
depth from kerb outwards, the milled material being windrowed to the side.
Pass No. 2:
The pre-milled material is incorporated into the 2200CR mixing drum, to be treated with
emulsion. Total recycled width after 2 passes 5.2m
Screed set up:
Pass No 1: The screed was set for 2.5m width to match the recycled width.
Pass No 2: The right hand section of the screed is set to 1.55m width, to match half the 2200CR
cutter width plus the pre milled section. The left hand screed width is set to 1.25m width, to match
half the 2200CR cutter width. Right hand screed section set to pave up to kerb edge. Total screed
width in Pass No. 2 is 2.8m.
Total 4 passes required for a 10.4m road width.
Laboratory and Field Evaluation of Recycled Cold Mixes 42
Figure2.19: Recycling option used
Figure 2-20: Emulsion tanker and recycler
Laboratory and Field Evaluation of Recycled Cold Mixes 43
Figure 2-21: Pre-compacted surface after 1st pass
Figure 2-22: Cold milling from kerb outwards
Laboratory and Field Evaluation of Recycled Cold Mixes 44
Figure 2-23: Pre-compacted surface after 2nd pass
Laboratory and Field Evaluation of Recycled Cold Mixes 45
2.16.4 Saudi Arabia – A desert road for heavy traffic The dual-lane Shaybah Access Road, with a total length of more than 380 km, leads from the
Batha main route to the Saudi Aramco Shaybah area in the Rub Al Khali desert. The construction
of a reliable traffic route was imperative for the development of an oil field with affiliated
refinery, and for the heavy-duty traffic to be expected in connection with the transport of
components for the processing plant weighing up to 200 t. Originally built from Marl as an
unbound gravel road only, the total length of the Shaybah Access Road was therefore recycled
within 180 days only using the foamed bitumen technology. During the main construction phase,
three Wirtgen Cold Recyclers WR 2500 and Mobile Slurry Mixing Plants WM 400 were in
operation on site. With the addition of 5% foamed bitumen and 2% cement slurry, a daily average
of approximately 35,000 m2 of existing pavement could be scarified and recycled with the binding
agents down to a depth of 20 cm. In order to optimise the workability and compaction properties
of the existing sub-base, which consisted of Marl and sand, approximately 4% water were added.
In addition to the Wirtgen machines WR 2500 and WM 400, motor graders as well as vibrating
rollers and pneumatic tired rollers were employed to profile and compact the treated material. In
order to ensure an optimum work pattern and to achieve the highest possible quality, two recycling
trains worked staggered behind one another, thus ensuring good adhesion between the individual
machine passes and an optimum profiling of the complete lane. This also enabled the heavy-duty
traffic to pass the ever moving job site during the whole duration of the rehabilitation project.
Finally, a bituminous surface treatment, in the form of a slurry seal, was applied on the recycled
base layer. In an inspection report, road construction experts praised the good suitability of foamed
bitumen as a stabilising agent even under these extreme climatic conditions, as well as its high
economic efficiency. The original plans involving conventional construction methods with
imported crushed aggregate and hot mix asphalt had been rejected as these would have met neither
the economical nor the time frame of this project. Figure 2-24 shows one of the three Wirtgen
recycling trains consisting of a WR 2500 and a Slurry Mixer WM 400 during the economical
rehabilitation of the Shaybah Access Road, In operation 24 hours a day despite extreme climatic
conditions.
Laboratory and Field Evaluation of Recycled Cold Mixes 46
Figure 2-24: Recycling of Shaybah Access road
Laboratory and Field Evaluation of Recycled Cold Mixes 47
2.16.5 In-Plant recycling using milled asphalt bound with foamed bitumen Responsible parties
Client: Durban Municipality, Roads Department - City Engineers Unit
Contractor: Milling Techniks
Design Engineers: Siyenza Engineers / Loudon International
Equipment suppliers: Wirtgen South Africa with Wirtgen GmbH (Germany)
Introduction
The Newlands West Drive, which serves as a mayor bus route and arterial to a large residential
area, showed signs of distress in the form of cracking of the existing asphalt layers. The
rehabilitation design called for an overlay on to the existing road of 125 mm thick foamed bitumen
stabilised RAP and 40 mm asphalt surfacing. The alternative conventional rehabilitation method
with the same structural capacity would have been to overlay the existing road with an 100 mm
asphalt binder layer and a 40 mm asphalt surfacing. Due to the increasing volume of stockpiled
RAP at the municipal depots and the relatively low stabilising agent contents required, the
alternative using the in-plant recycling method showed a significant saving for the client. This
project coincided with the 22nd PIARC World Road Congress. Thanks to the future orientated
thinking of the Durban Municipality, an agreement was reached together with Milling Techniks
and Wirtgen South Africa to showcase the in-plant recycling and foamed bitumen technology to
the international road construction industry attending the congress during the week of 20 . 24
October 2003.
Laboratory and Field Evaluation of Recycled Cold Mixes 48
Project details
Length of road: 1000 m, Width of road: 8 m
Aggregate: Reclaimed Asphalt Pavement (RAP) collected from
various milling contracts and stockpiled at the Durban City council’s
depot.
Stabilising agents: 2 % Foamed bitumen (80/100 penetration grade)
and 1 % cement (OPC)
Equipment utilized RAP sizing plant: Hartl PC 1270 I (Impact crusher)
Mixing Plant: Wirtgen KMA 200
Paving unit: Vögele Super 1800
Compactors: HAMM HD O70V double smooth drum with one
Vibratory and one Oscillation drum; and HAMM GRW 18
(pneumatic tyred roller)
Technical information
Design Life: 20 years
Structural capacity: 4,8 million ESALs (80 kN = 8 ton)
Mix properties: Indirect Tensile Strength (150 dia. briquette) > 150
KPa
Retained strength > 90 %
Unconfined Compressive Strength > 1500 KPa
Compaction: > 100 % of modified AASHTO density (1984 kg/m³)
Laboratory and Field Evaluation of Recycled Cold Mixes 49
Construction Method
A Hartl Power crusher PC 1270 impact crusher, was used to break down the oversized particles
within the RAP so that 100 % of the RAP could be utilized. This crushed material was then loaded
into the hopper of the Wirtgen KMA 200 by means of a Payloader. The KMA 200 cold mixing
plant was used to add the binding agents, being 2 % foamed bitumen, 1 % cement. In addition
1,5% to 2,0% water was added to achieve 90 % of the optimum moisture content. The cold mixed
material exiting out of the KMA 200 is loaded directly onto tip trucks and transported to
Newlands West drive, approximately 8 km away from the mixing plant area. The cold processed
material was then placed with a Vögele 1800 road paver. The TV screed on the paver equipped
with Tampers and Vibration achieved a very high degree of compaction. The layer thickness
directly behind the paving screed was 150 mm. To achieve the specified compaction (greater than
100 % of modified Proctor density) the rollers merely had to compact the material to a thickness
of 125 mm. The compaction was achieved with a HAMM HD 70 Oscillation tandem roller and a
HAMM GRW 18 pneumatic tyred roller. During final compaction a light spray of water was
applied. This resulted in a tight knit surface, which was resistant to the wear and tear of the traffic.
The foamed bitumen bound layer was trafficked immediately after final compaction was
completed. Before the second half was paved, the transverse tie-in joint was cut by means of a
grader. An alternative method of creating this tie-in joint would be by means of a W 350 milling
machine. The longitudinal joint was moistened by means of a water hosepipe and a water tanker. It
is the nature of the foamed bitumen material to be workable, even after many hours or even weeks
after mixing. Therefore the main advantages of using this cold treated material are that the layer
can be trafficking directly after compaction has been completed and because the entire process is a
cold process the cold joints merely need to be moistened to achieve good bonding. If the
transverse day joints and longitudinal construction joints are constructed as described, they are as
sound as the rest of the pavement. This is due to the nature of the foamed bitumen treated material,
i.e. bitumen rich mortar binding together the entire granular matrix, and the fact that particle
interlock is achieved. The finished cold recycled base course lay open without a wearing course
between 6 and 9 days, depending on the section. After this period a tack coat, using a stable 60
bitumen emulsion, was applied before a 4 cm Asphalt wearing course was paved.
Laboratory and Field Evaluation of Recycled Cold Mixes 50
Figure2-25: The Hartl Powercrusher PC 1270 I Impact crusher being used to crush the RAP
material.
Figure2-26: The Wirtgen KMA 200 cold mixing plant utilized to dose and mix the binding agents
and water with the RAP.
Laboratory and Field Evaluation of Recycled Cold Mixes 51
Figure 2-27: Vögele 1800 paving the foamed bitumen treated base material directly onto the road
as an overlay .
Figure 2-28: Compaction done with HAMM HD O70V double drum Oscillation / Vibration roller
and HAMM GRW 18 pneumatic tyred roller.
Laboratory and Field Evaluation of Recycled Cold Mixes 52
Figure2-29: The road surface being moistened with water during final compaction and just before
traffic is allowed onto the base course.
Figure2-30: The longitudinal joint being moistened before paving of the second road-width.
Laboratory and Field Evaluation of Recycled Cold Mixes 53
Figure 2-31: Paving of the second road width and traffic on the freshly compacted material. This
layer was kept moist for the first couple of hours for curing purposes.
Figure2-32: The finished cold recycled base course after being trafficked for several days.
Laboratory and Field Evaluation of Recycled Cold Mixes 54
Figure2-33: The Tack coat applied by a hand sprayer on one half of the base course.
Figure2-34: Paving and compaction of the 4 cm asphalt wearing course.
Laboratory and Field Evaluation of Recycled Cold Mixes 55
_________________________________________CHAPTER 3
3. LABORATORY AND FIELD STUDY
3.1 RAP and Mineral Aggregate Evaluation Representative sample of pulverized and air dried Reclaimed Asphalt Product (RAP) and Crusher
stone dust were collected from stock pile and then sieved through a set of sieves for gradation. The
details of sieve analysis are presented in tables 3.1 and 3.2. Bitumen content and moisture content
of air dried RAP found to be 5.2% and 0.12% respectively. Moisture content and specific gravity
of air dried Stone Dust found to be 0.40% and 2.68 respectively. Mineral fillers used in the present
study are hydrated lime of specific gravity 2.53, Ordinary Portland cement of 53-grade and Fly-
ash of specific gravity 2.12 (P-75µ=100%).
Table3. 7: Sieve analysis of pulverized and air-dried RAP sieve size,
mm 37.5 26.5 19 13.2 9.5 6.7 4.75 2.36 1.18 0.6 0.425 0.3 0.075 pan
cumulative % passing 100.0 99.2 95.0 74.7 52.1 39.1 29.1 16.6 7.5 5.3 3.4 2.0 0.2 0.0
Table3. 8: Sieve analysis of Stone Dust
sieve size, mm 6.7 4.75 2.36 1.18 0.6 0.425 0.3 0.075 pan cumulative % passing 100.00 93.40 72.00 50.60 43.60 35.80 26.20 9.00 0.00
3.2 Foamed Bitumen Characterization
The Study of foamed bitumen and its characterization wais carried out using Wirtgen Foam
bitumen Laboratory plant, WLB-10 (Figure 3.1). The Foamability and the variation of foam
characteristics viz. expansion ratio and half life time were observed at different air pressures,
temperatures and Bitumen water contents. Dip stick and stop watch were used to find foam
volume and half life. The height of foamed bitumen immediately after complete spray and after
complete foam collapse was found to determine the Expansion ratio. The discharging capacity of
bitumen pump found to be 125 grams/second and the injection time of foam adopted was
5seconds. The bitumen used was of 80/100 penetration grade. The graphs (figures 3.2, 3.3 and 3.3)
were plotted to determine the optimum foam producing air pressure, bitumen temperature, and
bitumen water content.
Study of Air pressure Influence on expansion ratio and half time of Foamed bitumen: The Bitumen water, 3% (i.e. Bitumen water discharge, 10.8 l/h) and Bitumen temperature, 165 0c
were kept constant and the air pressure was varied from 3 to 6 bars at an interval of 1 bar to study
Laboratory and Field Evaluation of Recycled Cold Mixes 56
the influence of air pressure. The bitumen water pressure was kept 1 bar more than the air pressure
as given in WLB-10 operation manual. Basic height of bitumen of 625 g per unit area of container
was found to be 1.2 cms after complete collapse of the foam. The graph plotted keeping air
pressure on X-axis and expansion ratio and half life were kept on Y-axis. From this study and
looking in to the figure 3.2 optimum Air pressure was decided as (3.85+4.8)/2 =4.325 bars,
fallowing the Minimum acceptable Bitumen foam parameters Expansion ratio 8 times and Half-
life time 6 seconds.
Study of Bitumen temperature Influence on expansion ratio and half time of Foamed bitumen
The Bitumen water, 3% (i.e. Bitumen water discharge, 10.8 l/h), Air pressure, 4.3 bars and
Bitumen water pressure, 5.3 bars were kept constant and Bitumen temperature was varied from
150 to 180 o C at an interval of 10 0C to study the variation of expansion ratio and half life time.
The graph plotted keeping Bitumen temperature on X-axis and expansion ratio and half life were
kept on Y-axis. From this study and looking in to the figure 3.3 optimum bitumen temperature was
decided as (154+156)/2 = 155 0C
Study of Bitumen water content Influence on expansion ratio and half life time of Foamed bitumen
The Air pressure, 4.3 bars, Bitumen water pressure, 5.3 bars and Bitumen temperature, 155 0C
were kept constant and Bitumen water content was varied from 8 to 15 liters per hour to study the
variation of expansion ratio and half life time. The graph plotted keeping Bitumen water content
on X-axis and expansion ratio and half life were kept on Y-axis. From this study and looking in to
the figure 3.4 optimum bitumen water content was decided as (2.7+3.8)/2=3.25 % of bitumen.
After studying the bitumen foam behaviour at different air pressures, temperatures and bitumen
water contents it is concluded to take optimum air pressure, temperature and bitumen water
contents as 4.3 bars, 155 to 160 0C and 12 l/h (i.e. 3.3% of bitumen) respectively to produce
acceptable bitumen foam and were fallowed while producing foamix.
Laboratory and Field Evaluation of Recycled Cold Mixes 57
Figure3. 5: WLB 10- Wirtgen foamed bitumen lab kit
Table3. 9: Air pressure Influence on expansion ratio and half time of Foamed bitumen
1st measurement
2nd measurement
3rd measurement
average value Air
pressure, bars
Maximum foam
height, in cm
Half life, s
Maximum foam
height, in cm
Half life, s
Maximum foam
height, in cm
Half life, s
Expansion ratio
Half life, s
3 8 8 10 7 9 8 7.50 7.67 4 9 7 9.5 8 8.5 8 7.50 7.67 5 11 5.5 13 5.5 11.5 5 9.86 5.33 6 12.5 4 13 4.5 12.5 5 10.56 4.50
3456789
101112
2.5 3 3.5 4 4.5 5 5.5 6 6.5Air pressure, bar
Expa
nsio
n ra
tio
0123456789
Hal
f life
, sec
onds
exp ratio
half life in seconds
Figure3. 6: Air pressure Influence on expansion ratio and half time of Foamed bitumen
Laboratory and Field Evaluation of Recycled Cold Mixes 58
Table3. 10: Bitumen temperature Influence on expansion ratio and half time of Foamed bitumen 1st measurement
2nd measurement
3rd measurement
average value
Bitumen
temparature,0C Maximum
foam height, in
cm
Half life, s
Maximum foam
height, in cm
Half life, s
Maximum foam
height, in cm
Half life, s Expansion ratio Half life, s
150 8 8 8.5 6 10 7.5 7.36 7.17 160 10 4 11 5.5 11 6 8.89 5.17 170 11 4.25 13 4.5 11.5 4.25 9.86 4.33 180 12.5 3.5 13 3.5 12 3 10.42 3.33
3456789
101112
145 150 155 160 165 170 175 180 185Temperature, 0C
Expa
nsio
n ra
tio
0123456789
Hal
f life
, sec
onds
exp ratio
half life in seconds
Figure3. 7: Bitumen temperature Influence on expansion ratio and half time of Foamed bitumen
Table3. 11: Study of Bitumen water content Influence on expansion ratio and half life time of Foamed bitumen
1st measurement
2nd measurement
3rd measurement
average value Bitumen
Water content,
%
Flow-through,
l/h
Maximum foam
height, in cm
Half life,
s
Maximum foam
height, in cm
Half life,
s
Maximum foam
height, in cm
Half life,
s
Expansion ratio
Half life, s
2.22 8 7 10 9.5 9.5 10.5 9 7.50 9.50 2.50 9 8.5 8 11.5 8 9.5 8 8.19 8.00 3.33 12 10 7 12 7 10.5 7 9.03 7.00 3.89 14 11 6 12.5 5.5 11 7.5 9.58 6.33 4.17 15 13.5 5 14 5 13.5 5 11.39 5.00
Laboratory and Field Evaluation of Recycled Cold Mixes 59
3456789
101112
2.0 2.5 3.0 3.5 4.0 4.5 Bitumen water content, %
Expa
nsio
n ra
tio
0123456789
Hal
f life
, sec
onds
exp ratio
half life
Figure3. 8: Bitumen water content Influence on expansion ratio and half life time of Foamed
bitumen
3.3 Emulsion Testing Table3. 12: Tests on Emulsion
Emulsion Property Observed value Specified value Residue on evaporation, Minimum % 66.5% 60% Viscosity, saybolt furol viscometer At 250C, seconds 48 30-150 Storage stability after 24 hours, Maximum 1.8% 2% Charge positive positive Miscibility with water No coagulation No coagulation Tests on residue: Penetration @250C, 100g, 5 seconds 85 60-120 Ductility @270C, cm, minimum 68 50
3.4 Mineral Aggregate Proportions Based on pulverized RAP and stone dust gradation their proportions were fixed to meet the
gradation requirement for Foamed bitumen treatment. Four different options of aggregate
proportions were chosen with different quantity of filler (table 3.7). And the same aggregate
proportions were fallowed for Emulsion treatment also. The details of aggregate proportions and
the gradation charts are given in Tables 3.8, 3.9, 3.10 and 3.11 and Figures 3.5, 3.6, 3.7 and 3.7
respectively.
Laboratory and Field Evaluation of Recycled Cold Mixes 60
Table3. 7: Different options of aggregate proportions RAP Stone Dust Filler Option: 1 54.00% 46.00% 0.00%
Option: 2 53.46% 45.55% 0.99% Option: 3 52.94% 45.10% 1.96%
Option: 4 52.40% 45.70% 2.90%
Table3. 8: Option1 Material proportions
Cumulative % passing Trials percentages specified limitssieve size, mm RAP SD RAP SD filler
combined grading upper lower
37.5 100 100 54.00 46.00 0.00 100.00 100.00 100.0026.5 99.24 100.00 53.59 46.00 0.00 99.59 100.00 85.37 19 95.02 100.00 51.31 46.00 0.00 97.31 100.00 73.33
13.2 74.72 100.00 40.35 46.00 0.00 86.35 86.81 62.07 9.5 52.12 100.00 28.14 46.00 0.00 74.14 76.63 53.37 6.7 39.17 100.00 21.15 46.00 0.00 67.15 67.34 45.44 4.75 29.10 93.40 15.71 42.96 0.00 58.68 59.52 38.75 2.36 16.66 72.00 9.00 33.12 0.00 42.12 46.89 27.97 1.18 7.58 50.60 4.09 23.28 0.00 27.37 37.75 20.16 0.6 5.32 43.60 2.87 20.06 0.00 22.93 31.20 14.56
0.425 3.46 35.80 1.87 16.47 0.00 18.34 28.55 12.30 0.3 2.03 26.20 1.09 12.05 0.00 13.15 26.26 10.35
0.075 0.25 9.00 0.14 4.14 0.00 4.28 20.00 5.00 Table3.9: Option2 Material proportions
Cumulative % passing Trials percentages specified
limits sieve size, mm RAP SD RAP SD filler
combined grading upper lower
37.5 100 100 53.47 45.55 0.99 100.00 100 100 26.5 99.24 100.00 53.06 45.55 0.99 99.59 100 85 19 95.02 100.00 50.80 45.55 0.99 97.34 100 73
13.2 74.72 100.00 39.95 45.55 0.99 86.48 87 62 9.5 52.12 100.00 27.86 45.55 0.99 74.40 77 53 6.7 39.17 100.00 20.94 45.55 0.99 67.48 67 45 4.75 29.10 93.40 15.56 42.54 0.99 59.09 60 39 2.36 16.66 72.00 8.91 32.79 0.99 42.69 47 28 1.18 7.58 50.60 4.05 23.05 0.99 28.09 38 20 0.6 5.32 43.60 2.84 19.86 0.99 23.69 31 15
0.425 3.46 35.80 1.85 16.31 0.99 19.15 29 12 0.3 2.03 26.20 1.08 11.93 0.99 14.01 26 10
0.075 0.25 9.00 0.14 4.10 0.99 5.22 20 5
Laboratory and Field Evaluation of Recycled Cold Mixes 61
Table3.10: Option3 Material proportions Cumulative %
passing Trials percentages specified limits sieve size, mm
RAP SD RAP SD fillercombined grading
upper lower 37.5 100 100 52.94 45.10 1.96 100.00 100 100 26.5 99.24 100.00 52.54 45.10 1.96 99.60 100 85 19 95.02 100.00 50.31 45.10 1.96 97.36 100 73
13.2 74.72 100.00 39.56 45.10 1.96 86.61 87 62 9.5 52.12 100.00 27.59 45.10 1.96 74.65 77 53 6.7 39.17 100.00 20.74 45.10 1.96 67.80 67 45 4.75 29.10 93.40 15.40 42.12 1.96 59.49 60 39 2.36 16.66 72.00 8.82 32.47 1.96 43.25 47 28 1.18 7.58 50.60 4.01 22.82 1.96 28.79 38 20 0.6 5.32 43.60 2.81 19.66 1.96 24.44 31 15
0.425 3.46 35.80 1.83 16.15 1.96 19.94 29 12 0.3 2.03 26.20 1.07 11.82 1.96 14.85 26 10
0.075 0.25 9.00 0.13 4.06 1.96 6.15 20 5
Table3.11: Option4 Material proportions Cumulative %
passing Trials percentages specified
limits sieve size, mm RAP SD RAP SD filler
combined grading upper lower
37.5 100 100 52.40 44.70 2.90 100.00 100 100 26.5 99.24 100.00 52.00 44.70 2.90 99.60 100 85 19 95.02 100.00 49.79 44.70 2.90 97.39 100 73
13.2 74.72 100.00 39.15 44.70 2.90 86.75 87 62 9.5 52.12 100.00 27.31 44.70 2.90 74.91 77 53 6.7 39.17 100.00 20.53 44.70 2.90 68.13 67 45 4.75 29.10 93.40 15.25 41.75 2.90 59.90 60 39 2.36 16.66 72.00 8.73 32.18 2.90 43.81 47 28 1.18 7.58 50.60 3.97 22.62 2.90 29.49 38 20 0.6 5.32 43.60 2.79 19.49 2.90 25.18 31 15
0.425 3.46 35.80 1.81 16.00 2.90 20.72 29 12 0.3 2.03 26.20 1.06 11.71 2.90 15.67 26 10
0.075 0.25 9.00 0.13 4.02 2.90 7.06 20 5
Laboratory and Field Evaluation of Recycled Cold Mixes 62
0
20
40
60
80
100
0.01 0.1 1 10 100
sieve size, mm (log scale)
Perc
ent
pass
ing
upper limitlower limit combinedRAPSD
Figure3. 5: option1 gradation curves
0
20
40
60
80
100
0.01 0.1 1 10 100sieve size, mm (log scale)
Perc
enta
ge p
assi
ng
lowerlimitupperlimitcombined achieved RAPstone dust
Figure3. 6: option2 gradation curves
Laboratory and Field Evaluation of Recycled Cold Mixes 63
0
20
40
60
80
100
0.01 0.1 1 10 100sieve size, mm (log scale)
Perc
enta
ge p
assi
ng
lowerlimitupperlimitcombined achieved RAPstone dust
Figure3. 7: option3 gradation curves
0
20
40
60
80
100
0.01 0.1 1 10 100sieve size, mm (log scale)
Perc
enta
ge p
assi
ng
lowerlimitupperlimitcombined achieved RAPstone dust
Figure3. 8: option4 gradation curves
Laboratory and Field Evaluation of Recycled Cold Mixes 64
3.5 OMC Determination for Foamed Bitumen Treatment The pulverized and air dried RAP is separated in to three different fractions fallowing the
procedure described in Appendix A (i.e. P-19mm & R-13.2mm, P-13.2mm & R4.75mm and P-
4.75). The proportioned (Option 1) and un-treated material was used to find Optimum Moisture
Content with modified Proctor compaction effort for foamed bitumen treatment. The Optimum
Moisture Content found to be 8.75% with a Maximum Dry Density of 2.09 g/cc. The mixing
moisture content of proportioned material was decided based on optimum moisture content (i.e.
OMC=8.75%) and air dried field sample moisture content to prepare foamix.
Figure3. 9: samples of separated RAP and stone dust
1.98
2.00
2.02
2.04
2.06
2.08
2.10
2.0 3.5 5.0 6.5 8.0 9.5 11.0
Moisture content, %
Dry
dens
ity, g
/cc
Figure3. 10: OMC determination
Laboratory and Field Evaluation of Recycled Cold Mixes 65
3.6 OFC Determination for Emulsion Treatment The Optimum Fluid Content (OFC) was determined based on maximum Indirect Tensile Strength
(ITS) and maximum bulk density of Marshall Specimen prepared with 1.5% hydrated lime,
proportioned material (option1), 4% binder (6.02% Emulsion) and at varied percentages of water
content. The ITS and Bulk density of the Marshall Specimen were determined after a curing
period of 72 hours at 40 0C temperature and the testing was conducted at ambient temperature.
The graph (figure 3.11) was plotted keeping total fluid content on X-axis and Bulk density and
ITS on Y-axis to determine the OFC of the Emulsion treated material. From the graph Optimum
Fluid Content was decided (10.5+10.75)/2 = 10.625%.
Note: Total fluid content includes field moisture content, emulsion and additional water.
2.0352.0402.045
2.0502.0552.0602.0652.070
2.0752.0802.085
9.0 9.5 10.0 10.5 11.0 11.5 12.0
Total fluid content, %
Bul
k de
nsity
, g/c
c
140160180
200220240260280
300320340
ITS.
KPa
Bulk density
ITS
Figure3. 11: OFC determination
Laboratory and Field Evaluation of Recycled Cold Mixes 66
3.7 Recycled Cold Mix Preparation with Foamed Bitumen The graded material and different fillers (Cement, Hydrated lime and Fly-ash) in different percentages was
mixed using pug-mill type mixer since the quantity of mix was 10 kg. Initially dry mixing of proportioned
material was carried out for 10 to 15 seconds then additional water was added and then in to that mix
foamed bitumen was sprayed using WLB-10 fallowing the procedure described in Appendix A.2, after
setting the calculated and determined parameters (table 3.12) on the laboratory plant.
Figure3. 12: Mineral aggregates used in the study
Figure3. 13: WLB10 laboratory plant used to produce foamed bitumen
Laboratory and Field Evaluation of Recycled Cold Mixes 67
Figure3. 14: Pug-mill type mixer used to prepare foamix
Laboratory and Field Evaluation of Recycled Cold Mixes 68
Table 3.12: Material calculations for foamix preparation Air dried moisture content of proportioned mix (RAP+SD), MC air dry= 0.25 %
Bitumen flow rate = 125 g/s OMC=8.75 % PUG MILL mixer time factor=1.0 sample with 0 % filler (Mf=0) Percent foam bitumen (Pfb) 2 3 4 5 Bulk mass of sample, g (M) 10000 10000 10000 10000 Dry Mass of sample (Md) Md= M (1+MC air dry/100) 9975.06 9975.06 9975.06 9975.06 % Water to be added, (Pw) Pw=1+(0.5xOMC-MC airdry) 5.13 5.13 5.13 5.13 Mass of water, g (Mw) Mw=Pw x (Md+Mf)/100 511.22 511.22 511.22 511.22 Mass of bitumen, g (Mb) Mb=Pfb x( Md+Mf)/100 199.50 299.25 399.00 498.75 Time to be set on WLB 10, s (T) T=1.0 xMb/125 1.60 2.39 3.19 3.99 sample with 1 % filler (mass of filler, Mf = 100 g ) Percent foam bitumen (Pfb) 2 3 4 5 Bulk mass of sample, g (M) 10000 10000 10000 10000 Dry Mass of sample,g (Md) Md= M (1+MC air dry/100) 9975.06 9975.06 9975.06 9975.06 % Water to be added, (Pw) Pw=1+(0.5xOMC-MC airdry) 5.13 5.13 5.13 5.13 Mass of water, g (Mw) Mw=Pw x (Md+Mf)/100 516.35 516.35 516.35 516.35 Mass of bitumen, g (Mb) Mb=Pfb x( Md+Mf)/100 201.50 302.25 403.00 503.75 Time to be set on WLB 10, s (T) T=1.0 xMb/125 1.61 2.42 3.22 4.03 sample with 2 % filler (mass of filler, Mf = 200 g ) Percent foam bitumen (Pfb) 2 3 4 5 Bulk mass of sample, g (M) 10000 10000 10000 10000 Dry Mass of sample,g (Md) Md= M (1+MC air dry/100) 9975.06 9975.06 9975.06 9975.06 % Water to be added, (Pw) Pw=1+(0.5xOMC-MC airdry) 5.13 5.13 5.13 5.13 Mass of water, g (Mw) Mw=Pw x (Md+Mf)/100 521.47 521.47 521.47 521.47 Mass of bitumen, g (Mb) Mb=Pfb x( Md+Mf)/100 203.50 305.25 407.00 508.75 Time to be set on WLB 10, s (T) T=1.0 xMb/125 1.63 2.44 3.26 4.07 sample with 3 % filler (mass of filler, Mf = 300 g ) Percent foam bitumen (Pfb) 2 3 4 5 Bulk mass of sample, g (M) 10000 10000 10000 10000 Dry Mass of sample,g (Md) Md= M (1+MC air dry/100) 9975.06 9975.06 9975.06 9975.06 % Water to be added, (Pw) Pw=1+(0.5xOMC-MC airdry) 5.13 5.13 5.13 5.13 Mass of water, g (Mw) Mw=Pw x (Md+Mf)/100 526.60 526.60 526.60 526.60 Mass of bitumen, g (Mb) Mb=Pfb x( Md+Mf)/100 205.50 308.25 411.00 513.75 Time to be set on WLB 10, s (T) T=1.0 xMb/125 1.64 2.47 3.29 4.11
Laboratory and Field Evaluation of Recycled Cold Mixes 69
3.8 Recycled Cold Mix Preparation with Emulsion The graded material and different fillers (Cement, Hydrated lime and Fly-ash) in different
percentages that were used in foamix preparation, the same combination of materials used except
the binder bitumen emulsion instead of foamed bitumen. Hobart mixer was used to prepare the
mixture since the material quantity was 1150 grams only. Three different percentages of bitumen
emulsions were tried, after mixing in the mixer a delay of 30 minutes elapsed to simulate field
condition and to ensure starting of emulsion breaking process before starting compaction.
Marshall Specimen was cast with the mixture, the number of blows applied were 75 on each side.
Figure 3.15: Hobart mixer used to prepare emulsion mixture
Laboratory and Field Evaluation of Recycled Cold Mixes 70
3.9 Foamed bitumen and Bitumen Emulsion treated RAP Specimen testing The Marshall specimen prepared with formulated material have been tested for Bulk Density,
Resilient modulus (MR) and Indirect Tensile Strength (ITS) after a curing period of 24 hours at
room temperature in mold and 72 hours at 40 0C after taken out of mold. And testing was carried
out at room temperature only. Duplicate samples were tested for soaked Indirect Tensile Strength
after a soaking period of 24 hours in water bath at ambient temperature. Indirect Tension Test for
Resilient Modulus was carried out at a repetitive load 100 N, frequency 0.1 Hertz and at a
temperature of 25 0C. The test results of bulk density, indirect tensile strength and Indirect Tension
test for Resilient Modulus are presented in tables 3.13 and 3.14 with different binders.
Field cores cut from the Foamed bitumen treated recycled pavement layer were tested for Bulk
Density, Resilient modulus (MR), Indirect Tensile Strength (soaked and un-soaked) and dynamic
creep resistance. Some Laboratory cast specimens were also tested for dynamic creep resistance
since the uniaxial unconfined creep test is effective in identifying the sensitivity of asphalt
mixtures to permanent deformation or rutting. Dynamic creep test was conducted under
unconfined conditions at a temperature of 40 0C. The Specimens were placed in the temperature
control cabinet for a minimum period of two hours for conditioning the specimen to achieve test
temperature before testing. The contact stress of 3 kPa was applied for 0.1 second and rest period
of 0.9 second at a frequency of 1 Hz. The load was applied for a maximum of 3600 cycles. The
details specimens and dynamic creep test results are presented in table 3.15.
Figure3.16: Indirect Tensile Strength Testing Schematic diagram
Laboratory and Field Evaluation of Recycled Cold Mixes 71
Figure3.17: Specimen setup of Indirect Tension Test for Resilient Modulus
Figure3.18: Specimen setup of dynamic creep testing
Laboratory and Field Evaluation of Recycled Cold Mixes 72
Table 3.13 Foamed bitumen Specimen test results ITS, kPa
Mold ID
Filler type
Filler, %
Foamed Bitumen, %
Bulk Density,
g/cc
Average Bulk
Density, g/cc
Resilient Modulus,
MPa
Mean Resilient Modulus, MPa
Dry Soaked
TSR, %
0/2/1 2.107 1211 316.74
0/2/2 2
2.063 2.085
1425 1318
183.41 58
0/3/1 2.114 2090 353.89
0/3/2 3
2.182 2.148
800 1445
259.87 73
0/4/1 2.134 1845 372.66
0/4/2 4
2.132 2.133
1528 1687
322.41 87
0/5/1 2.129 2544 402.01
0/5/2
0%
5 2.131
2.130 1765
2155 318.31
79
1c/2/1 Cement 2.340 2519 329.83
1c/2/2 Cement 2
1.964 2.152
1517 2018
292.94 89
1c/3/1 Cement 2.188 2585 390.23
1c/3/2 Cement 3
2.127 2.158
2250 2417
405.37 104
1c/4/1 Cement 2.126 2132 437.23
1c/4/2 Cement 4
2.125 2.125
2362 2247
387.04 89
1c/5/1 Cement 2.148 2335 450.46
1c/5/2 Cement
1%
5 2.074
2.111 2464
2399 343.44
76
2c/2/1 Cement 2.144 2094 435.79
2c/2/2 Cement 2
2.140 2.142
2244 2169
305.23 70
2c/3/1 Cement 2.161 2188 448.34
2c/3/2 Cement 3
2.139 2.150
2201 2195
403.76 90
2c/4/1 Cement 2.152 2278 519.35
2c/4/2 Cement 4
2.155 2.153
2286 2282
376.00 72
2c/5/1 Cement 2.126 2300 359.33
2c/5/2 Cement
2%
5 2.077
2.101 2253
2277 301.16
84
3c/2/1 Cement 2.163 1957 484.19
3c/2/2 Cement 2
2.120 2.141
2028 1993
433.83 90
3c/3/1 Cement 2.117 2494 494.21
3c/3/2 Cement 3
2.121 2.119
1802 2148
426.57 86
3c/4/1 Cement 2.114 2058 512.92
3c/4/2 Cement 4
2.118 2.116
2287 2173
402.82 79
3c/5/1 Cement 2.110 2258 500.38
3c/5/2 Cement
3%
5 2.095
2.102 2390
2324 382.34
76
1L/2/1 Lime 2.105 1458 319.45
1L/2/2 Lime 2
2.064 2.084
2417 1938
246.99 77
1L/3/1 Lime 2.076 2410 324.26
1L/3/2 Lime 3
2.072 2.074
1986 2198
239.23 74
1L/4/1 Lime 2.073 2026 350.48
1L/4/2 Lime 4
2.068 2.071
2197 2112
299.39 85
1L/5/1 Lime 2.052 2178 271.54
1L/5/2 Lime
1%
5 2.004
2.028 1970
2074 257.83
95
2L/2/1 Lime 2.134 2162 289.15
2L/2/2 Lime 2
2.091 2.112
1446 1804
278.04 96
2L/3/1 Lime 2.078 1664 312.80
2L/3/2 Lime
2%
3 2.097
2.087 2326
1995 267.68
86
Laboratory and Field Evaluation of Recycled Cold Mixes 73
2L/4/1 Lime 2.083 2469 316.85
2L/4/2 Lime 4
2.047 2.065
1549 2009
306.38 97
2L/5/1 Lime 2.018 2617 294.92
2L/5/2 Lime 5
2.026 2.022
2189 2403
262.45 89
3L/2/1 Lime 2.134 2504 304.66
3L/2/2 Lime 2
2.126 2.130
1474 1989
245.29 81
3L/3/1 Lime 2.101 1902 344.37
3L/3/2 Lime 3
2.118 2.109
2081 1992
302.73 88
3L/4/1 Lime 2.091 2502 354.63
3L/4/2 Lime 4
2.070 2.080
2245 2374
321.17 91
3L/5/1 Lime 2.066 3026 374.33
3L/5/2 Lime
3%
5 2.060
2.063 1802
2414 345.65
92
1F/2/1 Fly-ash 2.070 1073 144.56
1F/2/2 Fly-ash 2
2.097 2.084
1233 1153
36.76 25
1F/3/1 Fly-ash 2.070 1271 187.75
1F/3/2 Fly-ash 3
2.073 2.071
1445 1358
49.46 26
1F/4/1 Fly-ash 2.034 1331 192.45
1F/4/2 Fly-ash 4
2.081 2.057
1464 1398
61.06 32
1F/5/1 Fly-ash 2.032 2312 182.64
1F/5/2 Fly-ash
1%
5 2.015
2.024 1222
1767
2F/2/1 Fly-ash 1286
2F/2/2 Fly-ash 2
2.126 2.126
1344 1315
2F/3/1 Fly-ash 2.126 1409 187.88
2F/3/2 Fly-ash 3
2.109 2.118
1931 1670
61.57 33
2F/4/1 Fly-ash 2.110 1556 208.35
2F/4/2 Fly-ash 4
2.092 2.101
2110 1833
68.53 33
2F/5/1 Fly-ash 2.080 2143 166.07
2F/5/2 Fly-ash
2%
5
2.080
2143
3F/2/1 Fly-ash 2.086 979 197.16
3F/2/2 Fly-ash 2
2.097 2.092
879 929
62.33 32
3F/3/1 Fly-ash 2.042 1034 203.38
3F/3/2 Fly-ash 3
2.151 2.097
1375 1205
70.58 35
3F/4/1 Fly-ash 2.090 1687 211.73
3F/4/2 Fly-ash 4
2.100 2.095
948 1318
101.97 48
3F/5/1 Fly-ash 2.070 1638 221.03
3F/5/2 Fly-ash
3%
5 2.031
2.051 1663
1651 91.74
42
Field cores 1 Cement 1.5% 3.5% 2.110 3350 525.8072
2 Cement 1.5% 3.5% 2.090 2374 403.3839
3 Cement 1.5% 3.5% 2.108 3416 342.1538
4 Cement 1.5% 3.5% 2.035
2.090
2302
2861
258.0461
155
Lab Cores 2c/3.5/1 Cement 1.5% 3.5% 2.118 3133 245
2c/3.5/2 Cement 1.5% 3.5% 2.168 1974 259
2c/3.5/3 Cement 1.5% 3.5% 2.089
2.125
1411
2173
252
96
2L/3.5/1 Lime 1.5% 3.5% 2.130 3149 201
2L/3.5/2 Lime 1.5% 3.5% 2.135 1508 218
2L/3.5/3 Lime 1.5% 3.5% 2.063
2.109
971
1876
285
90
Laboratory and Field Evaluation of Recycled Cold Mixes 74
2F/3.5/1 Fly-ash 1.5% 3.5% 2.075 1371 109
2F/3.5/2 Fly-ash 1.5% 3.5% 2.127 1605 166
2F/3.5/3 Fly-ash 1.5% 3.5% 2.124
2.109
1240
1405
154
68
Table 3.14 Bitumen Emulsion Specimen test results
ITS, kPa Specimen ID
Filler type Filler Emulsion
% Binder
%
Bulk Density,
g/cc
Average Bulk
Density, g/cc
Resilient Modulus,
MPa
Average Resilient Modulus,
MPa Dry Soaked
TSR, %
0/3/1 4.51 3 2.037 1089 241.72
0/3/2 4.51 3 2.017 2.028
851 970
130.15 54
0/4/1 6.02 4 2.043 718 278.91
0/4/2 6.02 4 2.039 2.041
1137 928
252.88 91
0/5/1 7.52 5 2.051 1089 241.72
0/5/2
0%
7.52 5 2.037 2.044
949 1019
223.13 92
1c/3/1 4.51 3 2.127 1184 200.81
1c/3/2 4.51 3 2.118 2.123
809 997
219.41 109
1c/4/1 6.02 4 2.087 973 219.41
1c/4/2 6.02 4 2.092 2.090
1048 1011
226.84 103
1c/5/1 7.52 5 2.080 1319 185.94
1c/5/2
1%
7.52 5 2.065 2.073
1471 1395
211.97 114
2c/3/1 4.51 3 2.117 1075 178.50
2c/3/2 4.51 3 2.105 2.111
1012 1044
215.69 121
2c/4/1 6.02 4 2.084 1376 167.34
2c/4/2 6.02 4 2.102 2.094
1017 1197
208.25 124
2c/5/1 7.52 5 2.091 1271 167.34
2c/5/2
2%
7.52 5 2.086 2.089
1416 1344
185.94 111
3c/3/1 4.51 3 2.107 1288 148.75
3c/3/2 4.51 3 2.115 2.111
1387 1338
159.91 108
3c/4/1 6.02 4 2.109 1238 197.09
3c/4/2 6.02 4 2.075 2.092
1513 1376
215.69 109
3c/5/1 7.52 5 2.068 1748 204.53
3c/5/2
CEM
ENT
3%
7.52 5 2.078 2.073
914 1331
215.69 105
1L/3/1 4.51 3 2.049 1448 167.34
1L/3/2 4.51 3 2.049 2.050
1355 1402
141.31 84
1L/4/1 6.02 4 2.060 1254 182.22
1L/4/2 6.02 4 2.058 2.059
1346 1300
178.50 98
1L/5/1 7.52 5 2.096 1816 238.00
1L/5/2
1%
7.52 5 2.087 2.092
1474 1645
193.37 81
2L/3/1 4.51 3 2.030 1475 185.94
2L/3/2 4.51 3 2.045 2.038
1062 1268
133.87 72
2L/4/1 6.02 4 2.054 1551 159.91
2L/4/2 6.02 4 2.042 2.049
2174 1862
145.03 91
2L/5/1 7.52 5 2.062 2270 152.47
2L/5/2
2%
7.52 5 2.071 2.067
2095 2183
133.87 88
3L/3/1 4.51 3 2.045 1017 163.62
3L/3/2 4.51 3 2.007 2.026
2451 1734
152.47 93
3L/4/1
LIM
E
3%
6.02 4 2.031 2.036 2270 2007 215.69 90
Laboratory and Field Evaluation of Recycled Cold Mixes 75
3L/4/2 6.02 4 2.040 1743 193.37
3L/5/1 7.52 5 2.047 3012 174.78
3L/5/2 7.52 5 2.072 2.060
2348 2680
159.91 91
2c/3.5/1 2.111 2360 226.84
2c/3.5/2 2.103 2.107268
2041 2201
264.03 116
2L/3.5/1 2.105 1409 211.97
2L/3.5/2 2.085 2.095507
1574 1492
226.84 107
2F/3.5/1 2.075 763.5 122.72
2F/3.5/2
2% 5.26 3.5
2.084 2.080262
952.5 858
156.19 127
Table3.15: Dynamic Creep Test results
S.NO Mold description
Creep
stiffness,
MPa
Total accumulated
axial strain at 1 hour
of loading, %
Remarks
1 1.5% Cement, 3.5% Foamed
bitumen 464.7 0.015 No failure
2 1.5% Lime, 3.5% Foamed bitumen 103.124 0.066 No failure
3 1.5% Fly-ash , 3.5% Foamed
bitumen 32.897
0.207 No failure
4 1.5% Cement, 5.26% Bitumen
Emulsion (3.5% Binder) 11.565 0.585
No failure
5 1.5% Lime, 5.26% Bitumen
Emulsion (3.5% Binder) 2.7 2.492
Specimen failed at 1252nd cycle
6 1.5% Fly-ash, 5.26% Bitumen
Emulsion (3.5% Binder) 2.2 3.117
Specimen failed at 1054th cycle
7 Field core of 1.5% cement, 3.5%
Foamed bitumen 30.5 0.222
No failure
Laboratory and Field Evaluation of Recycled Cold Mixes 76
3.10 Benkelman Beam Deflection testing Benkelman beam deflection study has been carried out on the pavement constructed with
Recycled mix of Foamed bitumen after three months of construction i.e. in the month of March
2006. The interval of deflection measurement points is selected as 30 meters and initial point is
marked at a distance of 10 meters from the zero Chainage of the Road (i.e. NH-17 Junction). The
pavement temperature observed was 37 0 C, The PI value and moisture content of subgrade soil
found to be 14% and 17% respectively. The temperature correction factor and moisture correction
factor applied are -0.02 and 1.1 respectively. The average characteristic rebound deflection of the
pavement found to be 1.17mm. This road can serve to a 2 million standard axles without provision
of any overlay.
Table3.16: Deflection data (LHS, towards Karnataka cold Storage Pvt. ltd) Chainage, km & m 00+010 00+040 00+070 00+100 00+130 00+160 00+190 00+220 00+250 00+280 00+310
Distance, m 10 40 70 100 130 160 190 220 250 280 310
Corrected Rebound
Deflection, mm 0.89 0.66 1.18 0.37 0.62 0.65 0.31 0.62 0.37 1.03 1.31
Table3.17: Deflection data (RHS, towards Karnataka cold Storage Pvt. ltd) Chainage, km & m 00+010 00+040 00+070 00+100 00+130 00+160 00+190 00+220 00+250 00+280 00+310
Distance, m 10 40 70 100 130 160 190 220 250 280 310
Corrected Rebound
Deflection, mm 1.2 0.99 1.01 1.16 0.33 0.62 1.06 1.32 1.23 1.14 0.57
BBD study
0.00
0.30
0.60
0.90
1.20
1.50
0 30 60 90 120 150 180 210 240 270 300 330Distance, m
Reb
ound
Def
lect
ion,
m
m
RHS
LHS
Figure3.19: Benkelman Beam rebound deflection variation with distance
Laboratory and Field Evaluation of Recycled Cold Mixes 77
_________________________________________CHAPTER - 4
4. RESULTS AND ANALYSIS
4.1 Results of Foamed Bitumen Treated RAP Marshall Specimens
Bulk density:
The graphs are plotted to see the variation in bulk density with active filler and foamed bitumen.
The bulk density of the Marshall specimens was increased and then decreased as the foamed
bitumen content increases when there was no active filler. As the cement content increases there
was no significant increase in bulk density where as the binder increase causes a decrease in bulk
density. Maximum bulk density observed from graph 4.1a, was 2.16 g/cc at 3% foamed bitumen
and 1.1% cement.
When lime used as filler, increased bulk density was observed at increased lime content where as
increase in foamed bitumen decreased the bulk density. Maximum bulk density observed from
graph 4.1b, was 2.145 g/cc at 0% filler and 3% foamed bitumen and 2.13 g/cc at 3% lime and 2%
foamed bitumen.
Addition of fly-ash to the mix caused decrease in bulk density.
Table4.1: Maximum bulk density values from the Graphs 4.1(a, b, c)
Foamed bitumen, % Cement content, % Maximum bulk density, g/cc2 1.25 2.155 3 1.1 2.160 4 2 2.155 5 0 2.130
Foamed bitumen, % Lime content, % Maximum bulk density, g/cc2 3 2.130 3 0 2.145 4 0 2.120 5 0 2.130
Foamed bitumen, % Fly-ash content, % Maximum bulk density, g/cc2 1.75 2.125 3 0 2.150 4 0 2.120 5 0 2.130
Laboratory and Field Evaluation of Recycled Cold Mixes 78
Variation of Bulk density with Cement
2.0002.020
2.0402.0602.0802.100
2.1202.1402.1602.180
2.2002.220
0% 1% 2% 3% 4%Cement content, %
Bulk
den
sity
, g/c
c
2% Binder
3% Binder
4% Binder
5% Binder
Variation of Bulk density with Lime
2.0002.0202.0402.0602.0802.100
2.1202.1402.1602.1802.2002.220
0% 1% 2% 3% 4%Lime content, %
Bul
k de
nsity
, g/c
c
2% Binder
3% Binder
4% Binder
5% Binder
Variation of Bulk density with Fly ash
2.0002.0202.040
2.0602.0802.1002.1202.1402.160
2.1802.2002.220
0% 1% 2% 3% 4%Fly ash content, %
Bul
k de
nsity
, g/c
c
2% Binder
3% Binder4% Binder
5% Binder
Graph4. 2:( a, b, c) Variation of bulk density with foamed bitumen and filler
Laboratory and Field Evaluation of Recycled Cold Mixes 79
Resilient modulus (MR):
The values of Resilient modulus were plotted in graphs and then linear trend lines were drawn to
observe the variation in MR with foamed bitumen and active filler. It was observed from the
graphs 4.2 a, b that the increase in foamed bitumen and increase in cement increased the MR but at
higher cement contents and at higher foamed bitumen contents increase in MR was not much
significant. The optimum cement content ranges from 1 to 2% and optimum foamed bitumen
content ranges from 3 to 4%. The maximum MR values observed from the graphs 4.2a and b was
2372 MPa at 1% cement and 5% foamed bitumen and 2350 MPa at 3% cement and 3% foamed
bitumen. Similar trend was observed when the active filler used was lime with a difference of
significant increase in MR at higher contents of lime and foamed bitumen. The maximum MR
values observed from the graphs 4.3a and b was 2400 MPa at 3% lime and 5% foamed bitumen
and 2375 MPa at 3% lime and 4% foamed bitumen. When fly-ash used as filler the variation
observed was not much but at higher foamed bitumen contents there was an increase in MR. the
Maximum MR value observed from the graph 4.4 a and b was 2125 MPa at 2% fly ash and 5%
foamed bitumen.
Laboratory and Field Evaluation of Recycled Cold Mixes 80
Table 4.2: Maximum Resilient modulus (MR) values from the Graphs 4.2(a, b) Cement content, % Foamed bitumen, % Maximum Resilient modulus, MPa
0 5 2100 1 5 2372 2 5 2270 3 5 2250
Foamed bitumen, % Cement content, % Maximum Resilient modulus, MPa
2 3 2150 3 3 2350 4 3 2350 5 3 2350
Variation of MR with Foamed Bitumen and Cement
500750
10001250150017502000225025002750300032503500
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5Foamed bitumen, %
Res
ilien
t mod
ulus
, MPa
0% Filler
1% Cement
2% Cement
3% Cement
Variation of MR with Cement
500
1000
1500
2000
2500
3000
3500
0% 1% 2% 3% 4%Cement content, %
Res
ilien
t mod
ulus
, MPa
2% Foam bitumen
3% Foam bitumen
4% Foam bitumen
5% Foam bitumen
Graph4.2 :( a, b) Variation of Resilient Modulus with foamed bitumen and Cement
Laboratory and Field Evaluation of Recycled Cold Mixes 81
Table4.3: Maximum Resilient modulus (MR) values from the Graphs 4.3 (a, b) Lime content, % Foamed bitumen, % Maximum Resilient modulus, MPa
0 5 2100 1 5 2150 2 5 2300 3 5 2400
Foamed bitumen, % Lime content, % Maximum Resilient modulus, MPa
2 3 2000 3 3 2125 4 3 2375 5 3 2400
Variation of MR with Foamed bitumen and Lime
500750
10001250150017502000225025002750300032503500
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5Foamed bitumen, %
Res
ilien
t mod
ulus
, MPa
0% Filler
1% Lime
2% Lime
3% Lime
Variation of MR with Lime
500
1000
1500
2000
2500
3000
3500
0% 1% 2% 3% 4%Lime content, %
Res
ilien
t mod
ulus
, MPa
2% Foamed betumen
3% Foamed bitumen
4% Foamed bitumen
5% Foamed bitumen
Graph4.3 :( a, b) Variation of Resilient Modulus with foamed bitumen and Lime
Laboratory and Field Evaluation of Recycled Cold Mixes 82
Table4.4: Maximum Resilient modulus (MR) values from the Graphs 5.6(a, b) Fly-ash content, % Foamed bitumen, % Maximum Resilient modulus, MPa
0 5 2100 1 5 1700 2 5 2125 3 5 1650
Foamed bitumen, % Fly-ash content, % Maximum Resilient modulus, MPa
2 0 1350 3 0 1500 4 0 1700 5 0 2100
Variation of MR with Foamed bitumen and fly-ash
500750
10001250150017502000225025002750300032503500
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5Foamed bitumen, %
Res
ilien
t mod
ulus
, MPa
0% Filler
1% Flyash
2% Flyash
3% Flyash
Variation of MR with Flyash
500
1000
1500
2000
2500
3000
3500
0% 1% 2% 3% 4%Flyash content, %
Res
ilien
t mod
ulus
, MPa
2% Foamed bitumen
3% Foamed bitumen
4% Foamed bitumen
5% Foamed bitumen
Graph4.4 :( a, b) Variation of Resilient Modulus with foamed bitumen and Fly-ash
Laboratory and Field Evaluation of Recycled Cold Mixes 83
Indirect tensile strength (ITS):
The ITS values were increased and then decreased with increase in foamed bitumen. The addition
of cement increased the ITS values significantly. The maximum ITS observed was 510 kPa at 3%
cement and 4% foamed bitumen. When the crusher stone dust was replaced with lime it was
observed that the decrease in ITS initially and then at higher lime content slight increase. The
maximum ITS observed was 375 kPa at 3% lime and 5% foamed bitumen. Addition of fly ash
caused to decrease the ITS drastically. The specimens with cement and lime were observed to be
very less susceptible to moisture as it was observed from soaked ITS of the specimen.
Table 4.5: Maximum Dry Indirect Tensile Strength (ITS) values from the Graphs 4.5 (a, b, c)
Cement content, % Foamed bitumen, % Maximum Dry Indirect Tensile Strength, kPa0 5.00 400 1 5.00 450 2 3.25 490 3 4.00 510
Lime content, % Foamed bitumen, % 1 3.25 350 2 3.50 325 3 5.00 375
Fly-ash content, % Foamed bitumen, % 1 4.00 200 2 3.75 210 3 5.00 225
Table 4.6: Maximum soaked Indirect Tensile Strength (ITS) values
Cement content, % Foamed bitumen, % Maximum Soaked Indirect Tensile Strength, kPa0 4.50 325 1 3.75 400 2 3.50 400 3 2.00 430
Lime content, % Foamed bitumen, % 1 4.0 275 2 3.5 290 3 5.0 340
Fly-ash content, % Foamed bitumen, % 1 5 75 2 5 75 3 5 100
Laboratory and Field Evaluation of Recycled Cold Mixes 84
Variation of Dry ITS with Foamed bitumen and cement
050
100
150200250300350400
450500550
1.5 2 2.5 3 3.5 4 4.5 5 5.5Foamed bitumen, %
Dry
ITS,
KPa
0% Filler
1% Cement
2% Cement
3% Cement
Variation of Dry ITS with Foamed bitumen and lime
050
100150
200250
300350
400450
500550
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5Foamed bitumen, %
Dry
ITS,
KPa
0% Filler
1% Lime
2% Lime
3% Lime
Variation of Dry ITS with Foamed bitumen and fly-ash
050
100150200250300350400450500550
1.5 2 2.5 3 3.5 4 4.5 5 5.5
Foamed bitumen, %
Dry
ITS,
KPa
0% Filler
1% Flyash
2% Flyash
3% Flyash
Graph4.5: (a, b, c) Variation of dry ITS with foamed bitumen
Laboratory and Field Evaluation of Recycled Cold Mixes 85
4.2 Results of Emulsified Bitumen Treated RAP Marshall Specimens Bulk density:
The graphs are plotted to see the variation in bulk density with active filler and emulsified
bitumen. The bulk density of the Marshall specimens was decreased with increase in emulsion
binder content. Addition of cement increased the bulk density but as the cement content increases
there was no significant change in bulk density. Maximum bulk density observed was 2.12 g/cc at
3% binder and 1% cement.
When lime used as filler increased bulk density was observed to increase initially but as the lime
content increased it was decreased. Maximum bulk density observed from graph 4.6(a, b), was
2.14 g/cc at 3% lime and 2% emulsion binder.
Table4. 16: Maximum bulk density values From the Graphs 4.6 (a, b) Cement content, % Emulsion binder, % Maximum bulk density, g/cc
0 5 2.045 1 3 2.120 2 3 2.110 3 3 2.110
Lime content, % Emulsion binder, % Maximum bulk density, g/cc1 5 2.095 2 5 2.065 3 2 2.14
Variation of Bulk Density w ith Cement and emulsion
1.9802.0002.0202.0402.0602.0802.1002.1202.1402.1602.1802.200
0% 1% 2% 3% 4%Cement content, %
Bul
k D
ensi
ty, g
/cc
3% Binder
4% Binder
5% Binder
Variation of Bulk Density w ith Lime and emulsion
1.9802.0002.0202.0402.0602.0802.1002.1202.1402.1602.1802.200
0% 1% 2% 3% 4%
Lime content, %
Bul
k D
ensi
ty, g
/cc
3% Binder
4% Binder
5% Binder
Graph4.6 :( a ,b) Variation of bulk density with Bitumen Emulsion
Laboratory and Field Evaluation of Recycled Cold Mixes 86
Resilient modulus (MR): The values of Resilient modulus were plotted in graphs and then linear trend lines were drawn to
observe the variation in MR with emulsion and active filler. It was observed from the graphs 4.7 a,
b that MR was increased with both binder content and active fillers (lime and cement). The
increase in MR was not much significant with cement but with lime at 5% binder, increase in MR
was significant. In comparison with cement lime showed much better MR values at same binder
contents. The maximum MR values observed from the graphs 4.7a and b was 2650 MPa at 3%
lime and 5% emulsified binder and 1400 MPa at 3% cement and 3% emulsified binder.
Table4. 17: Maximum Resilient Modulus values from the Graphs 4.7 (a, b) Cement content, % Emulsion binder, % Maximum Resilient Modulus, MPa
0 5 1000 1 5 1350 2 5 1400 3 3,4,5 1400
Lime content, % 0 5 1000 1 5 1600 2 5 2250 3 5 2650
Variation of MR with Cement and emulsion
0
200
400
600
800
1000
1200
1400
1600
0% 1% 2% 3% 4%Cement content, %
Res
ilien
t mod
ulus
, MPa
3% Binder
4% Binder
5% Binder
Variation of MR with Lime and emulsion
0
500
1000
1500
2000
2500
3000
0% 1% 2% 3% 4%Lime content
Res
ilien
t mod
ulus
, MPa
3% Binder
4% Binder
5% Binder
Graph4.7 :( a, b) Variation of Resilient Modulus with Bitumen Emulsion
Laboratory and Field Evaluation of Recycled Cold Mixes 87
Indirect tensile strength (ITS):
The ITS values were increased and then decreased with increase in emulsion. The addition of
cement decreased the ITS. The maximum dry and soaked ITS observed was 275 kPa at 0% cement
and 4% binder and 250 kPa at 0% cement and 4% binder respectively. Addition of lime caused to
decrease the ITS. The specimens with cement and lime were observed to be very less susceptible
to moisture as it was observed from soaked ITS of the specimen. It was observed that soaked ITS
of cement treated material was slightly more than the dry ITS.
Table 4. 18: Maximum Dry and Soaked Indirect Tensile Strength (ITS) values from the Graphs 4.8 (a, b) and 4.9 (a, b).
Cement content, % Emulsion binder, % Maximum Dry Indirect Tensile Strength, KPa 0 4 275 1 4 220 2 3 175 3 4.5 200
Cement content, % Emulsion binder, % Maximum Soaked Indirect Tensile Strength, KPa0 4 250 1 4 225 2 3 220 3 4 220
Lime content, % Emulsion binder, % Maximum Dry Indirect Tensile Strength, kPa 1 5 240 2 3 180 3 4 220
Lime content, % Emulsion binder, % Maximum Soaked Indirect Tensile Strength, kPa 1 5 190 2 4 150 3 4 200
Laboratory and Field Evaluation of Recycled Cold Mixes 88
Variation of Dry ITS with emulsion and cement
0
50
100150
200
250
300
350
400450
500
550
2.5 3.0 3.5 4.0 4.5 5.0 5.5Binder content, %
ITS,
KPa
0% Filler
1% Cement
2% Cement
3% Cement
Variation of Soaked ITS w ith emulsion and cement
50
100
150
200
250
300
350
400
450
500
550
2.5 3.0 3.5 4.0 4.5 5.0 5.5Binder content, %
ITS,
KPa
0% filler
1% cement
2% Cement
3% cement
Graph4.8: (a, b) Variation of ITS with Bitumen Emulsion and Cement
Variation of Dry ITS w ith emulsion and lime
050
100150200250300350400450500550
2.5 3.0 3.5 4.0 4.5 5.0 5.5Binder content, %
ITS,
KPa
0% Filler
1% Lime
2% Lime
3% Lime
Variation of Soaked ITS w ith emulsion and lime
050
100150200250
300350400450500550
2.5 3.0 3.5 4.0 4.5 5.0 5.5Binder content, %
ITS,
KPa
0% filler
1% Lime
2% Lime
3% Lime
Graph4.9 :( a, b) Variation of ITS with Bitumen Emulsion and lime
Laboratory and Field Evaluation of Recycled Cold Mixes 89
4.3 Field and Laboratory Core Comparison Comparison of Field cores and Lab cores were made with same binder i.e. foamed bitumen 3.5%
and different fillers of 1.5% (Viz. Cement, Lime and Fly-ash). The MR and ITS of field cores
were higher than the laboratory cast cores but the bulk density of the field cores were less when
compared with laboratory cast cores. MR and ITS of Laboratory Cores with fly-ash were poor
when compared with filler as lime or cement.
Resilient Modulus variation in different cores
2861
21731876
1405
0
500
1000
1500
2000
2500
3000
3500R
esili
ent m
odul
us, M
Pa
Field core Lab core with CementLab core with Lime Lab core with Flyash
Dry ITS Variation in different cores
300
256 243
160
0
50
100
150
200
250
300
350
ITS
, kPa
Field core Lab core with cementLab core with Lime Lab core with Flyash
Variation of bulk density in different cores
2.0902.125 2.109 2.109
2.0002.0202.0402.0602.0802.1002.1202.1402.1602.1802.2002.220
Bulk
den
sity
, g/c
c
Field core lab core with Cement
lab core with Lime lab core with Flyash Graph4.10 :( a, b, c) Variation of Resilient Modulus, Bulk density and ITS in different cores
Laboratory and Field Evaluation of Recycled Cold Mixes 90
4.4 Dynamic Creep Test Results Analysis Laboratory cores prepared with foamed bitumen and cement were very strong against dynamic
axial loading in comparison with any other cores, even field cores. Field cores have shown very
poor resistance in comparison with laboratory cores. Accumulated axial strain was nominal in case
of foamed bitumen treated cores in comparison with emulsion treated cores. The cores treated with
emulsion & lime and emulsion & fly ash have failed before completion of total number of loading
cycles. Laboratory cores with emulsion and cement have shown better resistance in comparison
with other emulsion treated cores.
At 3.5%Foamed bitumen and 1.5% filler
0
0.05
0.1
0.15
0.2
0.25
0 1000 2000 3000 4000
Number of cycles
Acu
mul
ated
axi
al s
trai
n, %
cement
lime
fly-ash
field core
At 5.25% Emulsion(3.5% Binder) and 1.5% filler
0
0.5
1
1.5
2
2.5
3
3.5
0 1000 2000 3000 4000Number of cycles
Acc
umul
ated
axi
al s
trai
n, %
cement
lime
fly-ash
Graph4.11 :( a, b, c) Variation of Accumulated axial strain with Number of cycles
Laboratory and Field Evaluation of Recycled Cold Mixes 91
At 3.5% binder and 1.5% cement
0
0.1
0.2
0.3
0.4
0.5
0.6
0 1000 2000 3000 4000
Number of cycles
Acc
umul
ated
axi
al s
trai
n, %
foamed botumen
Emulsion
At 3.5% binder and 1.5% Lime
0
0.5
1
1.5
2
2.5
3
0 1000 2000 3000 4000
Number of cycles
Acc
ulm
ulat
ed a
xial
str
ain,
% Emulsion
Foamed bitumen
At 3.5% binder and 1.5% flyash
0
0.5
1
1.5
2
2.5
3
3.5
0 1000 2000 3000 4000Number of cycles
Acc
umul
ated
sxi
al s
trai
n, %
Emulsion
Foamed bitumen
Graph4.12 :( a, b) Variation of Accumulated axial strain with Number of cycles
Laboratory and Field Evaluation of Recycled Cold Mixes 92
________________________________________CHAPTER – 5
5. CONCLUSIONS The following conclusions are drawn based on the studies performed on emulsion treated and
foamed bitumen treated RAP in laboratory and Field.
In comparison with bitumen emulsion, foamed bitumen treated RAP has shown better
bulk density, indirect tensile strength, resilient modulus and dynamic creep stiffness
with same aggregate and gradation
Loss of strength on soaking is very less with foamed bitumen and lime/cement treated
material, in most of the cases the tensile strength ratio ranges from 70 to 100% and it
is 155% in case of field cores
Emulsion treated RAP with cement has shown higher soaked ITS than dry ITS
In view of bulk density, indirect tensile strength, resilient modulus and dynamic creep
stiffness, out of three fillers used in the present study cement has shown best results in
combination with foamed bitumen and the optimum cement content ranges from 1 to
2% by weight aggregates. At higher cement contents improvement in properties are not
much significant
Lime has shown almost similar densities, ITS and MR values to compare with cement
treated materials at higher lime contents
Fly-ash in combination with foamed bitumen of 5% has shown a minimum MR of
1500 MPa and minimum dry ITS of 200 kPa. In combination with cement and foamed
bitumen the fly-ash could be a use full material to treat the existing materials
Loss of ITS on soaking in fly-ash and foamed bitumen treated RAP was considerable
i.e. tensile strength ration ranges from 25 to 50%
Cores cut from the foamed bitumen treated pavement have shown higher ITS and MR
values in comparison with laboratory cast cores
Dynamic creep stiffness of Cores from the field was very less in comparison with
laboratory cast cores but they were comparable to HMA cores
Benkelman beam deflection study on foamed bitumen treated pavement shows that it
was structurally sound with an average characteristic rebound deflection of 1.17mm
and no functional failure was observed
Laboratory and Field Evaluation of Recycled Cold Mixes 93
________________________________________CHAPTER – 6
6. APPENDICES
Appendix 1: Material Sampling and blending 1.1 Field sampling
Bulk samples are obtained during field investigations and test pit excavations. Each layer in the
upper pavement (± 300 mm) must be sampled separately and at least 150 kg of material is
recovered from each layer that is likely to be included in any mix design procedure.
1.2 Preparation of samples for mix design procedure
1.2.1 Standard soil tests
Determine the grading (ASTM D 422) and plasticity index (ASTM D 4318) of the material
sampled from each individual layer.
1.2.2 Sample blending
Where necessary, blend the materials sampled from the different layers to obtain a combined
sample representing the material from the full recycling depth. The in-situ density of the various
components must be considered when blending materials, as illustrated in the boxed example
below. Repeat the tests described in 1.2.1 above to determine the grading and plasticity index of
the blended sample.
1.2.3 Representative proportioning
Separate the material in the representative sample into the following four fractions:
i. Retained on the 19.0 mm sieve;
ii. Passing the 19.0 mm sieve, but retained the 13.2 mm sieve;
iii. Passing the 13.2 mm sieve, but retained on the 4.75 mm sieve; and
iv. Passing the 4.75 mm sieve.
Laboratory and Field Evaluation of Recycled Cold Mixes 94
Reconstitute representative samples in accordance with the grading 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:
If there is insufficient material (i.e. passing the 19.0 mm sieve but retained on the 13.2 mm sieve)
for substituting that retained on the 19 mm sieve, then lightly crush the material retained on the
19.0 mm sieve to provide more of this fraction.
1.2.4 Sample quantities
The guidelines shown in Table 7.1 should be used for the quantity of material required for the
respective tests:
Table 7.1
Test Sample quantity required
Modified proctor, AASHTO T180 5 x 7 kg
Indirect Tensile Strength (150mm Dia) 20 kg per stabiliser content
Unconfined Compressive Strength (150mm Dia) 20 kg per stabiliser content
Bituminous Stabilization Design (Marshall briquettes) Minimum 10 kg per stabiliser content
Moisture contents Approximately 1kg
1.2.5 Hygroscopic 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 105 ºC and 110 ºC 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.
Laboratory and Field Evaluation of Recycled Cold Mixes 95
Appendix 2: Mix Design Procedure for Bitumen Stabilised Materials
2.1 Active filler requirements Bitumen stabilisation is normally carried out in combination with a small amount of active filler
(cement or hydrated lime). 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% Cement Add 1% Lime Pre-treat with 2% Lime
Pretreatment requires that the lime and water be added at least 4 hours prior to the addition of the
bitumen emulsion or 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.
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. Additional tests without active filler and/or with crusher dust are carried out
during the mix design process. The results of these tests allow a decision to be made as the
whether the addition of an active filler or crusher dust is warranted.
Laboratory and Field Evaluation of Recycled Cold Mixes 96
2. 2 Determination of Optimum Fluid Content (OFC) and Maximum Dry
Density (MDD) for the treated material
Note: For foamed bitumen stabilisation, the OFC and MDD can be assumed to be the same as the
OMC and MDD determined for representative samples of the untreated material.
The OFC for bitumen emulsion treated material is the percentage by mass of bitumen emulsion
plus additional moisture required to achieve the maximum dry density in the treated material. As
described below, the OFC is determined by adding a constant percentage of bitumen emulsion
whilst varying the amount of water added.
STEP 1
Measure out the bitumen emulsion as a percentage by mass of the air-dried material for each of
five prepared samples. The percentage of bitumen emulsion added is normally between 2 and 3%
residual bitumen (e.g. for 3% residual bitumen, add 5% of a 60 % bitumen emulsion).
STEP 2
The bitumen emulsion and water is added to the material and mixed until uniform immediately
prior to compacting the specimens.
STEP 3
Determine the OFC and MDD for the stabilised material in accordance with the modified
moisture-density relationship test procedure (AASHTO T-180).
Laboratory and Field Evaluation of Recycled Cold Mixes 97
2. 3 Preparation of bitumen stabilised material
2. 3.1 Preparation of materials for bitumen emulsion stabilization
STEP 1
Place the required quantity of sample into a suitable mixing container (10 kg for the manufacture
of 100 mm diameter briquettes, or 20 kg for the manufacture of 150 mm diameter briquettes).
STEP 2
Determine the dry mass of the sample using equation
Msample = Mair-dry / (1 + (Wair-dry / 100))
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 percentage of active filler (lime or cement) using equation
Mcement = (Cadd / 100) x Msample
Where: Mcement = mass of lime or cement to be added [g]
Cadd = percentage of lime or cement required [% by mass]
Msample = dry mass of the sample [g]
STEP 4
Determine the required percentage (by mass) of bitumen emulsion using equation
Memul = (RBreqd / PBE) x Msample
Where: Memul = mass of bitumen emulsion to be added [g]
RBreqd = percentage of residual bitumen required [% by mass]
PBE = percentage of bitumen in emulsion [% by mass]
Msample = dry mass of the sample [g]
STEP 5
Determine the amount of water to be added for optimum compaction purposes using equation
Mwater = {((WOFC – Wair-dry) / 100) x Msample} – Memul
Where: WOFC = optimum fluid content [% by mass]
Wair-dry = moisture content of air-dried sample [% by mass]
Mwater = mass of water to be added [g]
Laboratory and Field Evaluation of Recycled Cold Mixes 98
Memul = mass of bitumen emulsion to be added [g]
Msample = dry mass of the sample [g]
STEP 6
Mix the material, active filler, bitumen emulsion and water together until uniform. Immediately
manufacture briquette specimens following the relevant procedure for either 100 mm or 150 mm
diameter briquettes.
STEP 7
Samples are taken during the compaction process to determine the moulding moisture content.
2.3.2 Preparation of materials for foamed bitumen stabilization
2.3.2.1 Determination of the foaming properties of the bitumen
The foaming properties of each bitumen type are characterized 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 a particular source
of bitumen. This is achieved at three different bitumen temperatures as follows:
STEP 1
Heat the bitumen in the kettle of the Wirtgen WLB 10 laboratory unit with the pump circulating
the bitumen through the system until the required temperature is achieved (normally starting with
160 °C). Maintain the required temperature for at least 5 minutes prior to commencing with
testing.
STEP 2
Calibrate the discharge rate of the bitumen and set the timer on the Wirtgen WLB 10 to discharge
500 g of bitumen.
STEP 3
Set the water flow-meter to achieve the required water injection rate (normally starting with 2% by
mass of the bitumen).
STEP 4
Laboratory and Field Evaluation of Recycled Cold Mixes 99
Discharge foamed bitumen into a preheated (± 75 °C) steel drum for a calculated spray time for
500 g of bitumen. Immediately after the foam discharge stops, start a stopwatch.
STEP 5
Using the dipstick supplied with the Wirtgen WLB 10 (which is calibrated for a steel drum of 275
mm in diameter and 500 g of bitumen) measure the maximum height the foamed bitumen achieves
in the drum. This is recorded as the maximum volume.
STEP 6
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 7
Repeat the above procedure three times or until similar readings are achieved.
STEP 8
Repeat steps 3 to 7 for a range of at least three water injection rates. Typically, values of 2%, 3%
and 4% by mass of bitumen are used.
STEP 9
Plot a graph of the expansion ratio versus half-life at the different water injection rates on the same
set of axes (see the example in Figure 7.1). The optimum water addition is chosen as an average of
the two water contents required to meet these minimum criteria.
Repeat Step 1 to 9 for two other bitumen temperatures (normally 170 °C and 180 °C).
Laboratory and Field Evaluation of Recycled Cold Mixes 100
Figure 7.1 Determination of optimum foaming water content
The temperature and optimum water addition that produces the best foam is then used in the mix
design procedure described below.
Note: The minimum foaming properties that are acceptable for effective stabilisation are:
Expansion ratio: 8 times
Half-life: 6 seconds
If these minimum requirements cannot be met, the bitumen should be rejected as unsuitable for
foaming.
2. 3.2.2 Sample preparation for foamed bitumen treatment
STEP1
Place the required quantity of sample into a suitable mixing container (10 kg for the manufacture
of 100 mm diameter briquettes, or 20 kg for the manufacture of 150 mm diameter briquettes).
STEP2
Determine the dry mass of the sample using equation
Msample = Mair-dry / (1 + (Wair-dry / 100))
Laboratory and Field Evaluation of Recycled Cold Mixes 101
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]
STEP3
Determine the required percentage of active filler (lime or cement) using equation
Mcement = (Cadd / 100) x Msample
Where: Mcement = mass of lime or cement to be added [g]
Cadd = percentage of lime or cement required [% by mass]
Msample = dry mass of the sample [g]
STEP4
Determine the percentage of water to be added for optimum mixing moisture content as calculated
using equation A. The amount of water to be added to the sample is determined using equation B.
Wadd = 1 + (0.5 WOMC – Wair-dry) ---------------- [Equation A]
Mwater = (Wadd / 100) x (Msample + Mcement) ------- [Equation B]
Where: Wadd = water to be added to sample [% by mass]
WOMC = optimum moisture content [% by mass]
Wair-dry = water in air-dried sample [% by mass]
Mwater = mass of water to be added [g]
Msample = dry mass of the sample [g]
Mcement = mass of lime or cement to be added [g]
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 at 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 foamed bitumen to be added using equation:
Mbitumen = (Badd / 100) x (Msample + Mcement) Where: Mbitumen= mass of foamed bitumen to be added [g]
Laboratory and Field Evaluation of Recycled Cold Mixes 102
Badd = foamed bitumen content [% by mass]
Msample = dry mass of the sample [g]
Mcement = mass of lime or cement to be added [g]
STEP 7
Determine the timer setting on the Wirtgen WLB 10 using equation:
T = factor x (Mbitumen + Qbitumen) Where: T = time to be set on WLB 10 timer [s]
Mbitumen= mass of foamed bitumen to be added [g]
Qbitumen= bitumen flow rate for the WLB 10 [g/s]
factor = compensation for bitumen losses on the mixing equipment.
Experience has shown that a factor of 1.1 is applicable where a Hobart mixer is used and 1.0 when
using a pug mill-type 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 10 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 amount of water required to bring the sample to the optimum moisture content
using equation.
Mplus = (WOMC – Wsample) / 100 x (Msample + Mcement) Where: Mplus = mass of water to be added [g]
WOMC = optimum moisture content [% by mass]
Wsample = moisture content of prepared sample [% by mass]
Msample = dry mass of the sample [g]
Mcement = mass of lime or cement to be added [g]
STEP 11
Add the additional water and mix until uniform.
STEP 12
Laboratory and Field Evaluation of Recycled Cold Mixes 103
Transfer the foamed bitumen treated material into a container and immediately seal the container
to retain moisture. To minimize moisture loss from the prepared sample, manufacture briquette
specimens as soon as possible following the relevant procedure for either 100 mm or 150 mm
diameter briquettes.
Repeat the above steps for at least four different foamed bitumen contents.
2.3.4 Manufacture of 100 mm diameter briquette specimens
2.3.4.1 Compaction (Marshall Method)
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 1150 g 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. Care must be taken to
ensure the continuous free fall of the hammer.
STEP 4
Remove the mould and collar from the pedestal, invert the briquette (turn over). Replace it 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.
2.3.4.2 Curing procedure
Place the briquettes on a smooth flat tray and cure in a forced-draft oven for 72 hours at 40 °C. Remove
from oven after 72 hours and allow cooling to ambient temperature.
.2.3.5 Determination of optimum bitumen content for bitumen stabilised materials
Laboratory and Field Evaluation of Recycled Cold Mixes 104
The 100 mm diameter briquettes are tested for indirect tensile strength under dry and soaked conditions.
The results of the dry and soaked ITS tests are plotted against the respective bitumen content that
was added. The added bitumen content that best meets the desired properties is regarded as the
optimum bitumen content.
2.3.6. Compaction (modified AASHTO T-180 method)
STEP 1
Prepare and treat 24 kg of sample at the optimum bitumen content.
STEP 2
Where required, add sufficient moisture to bring sample to optimum compaction moisture content
and mix until uniform. Immediately after mixing, place material in an airtight container.
STEP 3
Take ±1 kg representative samples after compaction of the first and third briquette and dry to a
constant mass. Determine the moulding moisture using equation
Wmould = (Mmoist – Mdry) / Mdry x 100
Where: Wmould = moulding moisture content [% by mass]
Mmoist = mass of moist material [g]
Mdry = mass of dry material [g]
STEP 4
Compact at least 4 briquettes using a 150 mm diameter split-mould, applying modified AASHTO
(T-180) compaction effort (5 layers approximately 25 mm thick, 55 blows per layer using a 4.536
kg hammer with a 457 mm drop).
STEP 5
Carefully trim excess material from briquettes, as specified in the AASHTO T-180 test method.
STEP 6
Carefully remove briquette from the spilt-mould and place on a smooth flat tray. Allow to stand at
ambient temperature for 24 hours or until the moisture content has reduced to at least 50 % of
OMC.
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.
Laboratory and Field Evaluation of Recycled Cold Mixes 105
Appendix 3: Strength Test Procedures
3.1 Determination of Indirect Tensile Strength (ITS)
The ITS test is used to test the briquettes under different moisture conditions including dry, soaked
and equilibrium moisture content. 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/minute 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 load 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). This moisture content is used to determine the dry
density of the briquette.
STEP 5
Calculate the ITS for each briquette to the nearest 1 kPa using equation
ITS = (2 x P) / (∏ x h x d) x 10000
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 repeat steps 1 to 5.
The “Tensile Strength Retained (TSR)” is the relationship between the soaked and un-soaked ITS
Laboratory and Field Evaluation of Recycled Cold Mixes 106
for a specific batch of briquette specimens, expressed as a percentage using equation
TSR = Soaked ITS / Un-soaked ITS x 100
Laboratory and Field Evaluation of Recycled Cold Mixes 107
3.2 Indirect Tension Test for Resilient Modulus of Bituminous mixtures :( ASTM D 4123-82) Summery of test method
• The repeated load indirect tension test for determining resilient modulus of bituminous
mixtures is conducted by applying compressive loads with a haversine or other suitable
wave form. The load is applied vertically in the vertical diametrical plane of a cylindrical
specimen of asphalt concrete. The resulting horizontal deformation of the specimen is
measured and with an assumed Poisson’s ratio, is used to calculate a resilient modulus. A
resilient Poisson’s ratio can also be calculated using the measured recoverable vertical and
horizontal deformations.
• Interpretation of the deformation data as resulted in two resilient modulus values being
used. The instantaneous resilient modulus is calculated using the recoverable deformation
that occurs instantaneously during the unloading portion of one cycle. The total resilient
modulus is calculated using the total recoverable deformation which includes both
instantaneous recoverable and the time dependent continuing recoverable deformation
during the unloading and rest-period portion of one cycle.
Significance and use:
• The values of resilient modulus can be used to evaluate the relative quality of materials as
well as to generate input for pavement design or pavement evaluation and analysis. The
test can be used to study effects of temperature, loading rate, rest periods etc. since the
procedure is non-destructive, tests can be repeated on a specimen to evaluate conditioning
as with temperature or moisture. This test method is not intended for use in specifications.
Laboratory and Field Evaluation of Recycled Cold Mixes 108
_________________________________________CHAPTER - 7
7. REFERENCES Websites
1. www.asphalt.csir.co.za
2. www.arra.org
3. www.infra.com
4. www.wirtgen.com
Reports and papers
1. Wirtgen cold recycling manual-2004
2. Wirtgen job reports
3. Dr. Bose.S, Dr. Sangita, M.P. singh & Girish Sharma “Use of cold mix recycling for
rehabilitation of flexible pavements"
4. CAPSA'99 - Muthen et al: Foamed Asphalt Mixes Mix Design Procedure
5. Ramanujam, J.M. & Fernando, D.P. 1997. Foam Bitumen Trial at Gladfield-Cunningham
Highway. In: Proceedings of the Southern Region Symposium, Australia, 1997.
6. A Basic asphalt emulsion manual “Manual Series No.19” third edition
7. TRL Report TRL645 “Feasibility of recycling thin surfacing back in to thin surfacing
systems”
8. CAPSA'99 - Jenkins et al: Characterisation Of Foamed Bitumen
9. CAPSA'99 - Engelbrecht: Manufacturing Foam Bitumen In A Standard Drum Mixing
Asphalt Plant
10. Capsa'99 - Lewis: Cold In Place Recycling: A Relevant Process For Road Rehabilitation
And Upgrading
11. Acott, S.M. & Myburgh, P.A. 1983. Design and performance study of sand bases treated
with foamed asphalt. In: Low-volume roads: third international conference. Washington,
DC: (Transportation Research Record; 898), pp 290-296.
12. Acott, S.M.1979. Sand stabilisation using foamed bitumen. In: 3rd Conference on Asphalt
Pavements for Southern Africa, 3rd, 1979, Durban, pp.155-172.
Laboratory and Field Evaluation of Recycled Cold Mixes 109
13. Akeroyd, F.M.L. & Hicks, B.J. 1988. Foamed Bitumen Road Recycling. Highways,
Volume 56, Number 1933, pp 42, 43, 45.
14. Akeroyd, F.M.M. 1989. Advances in foamed bitumen technology. In: Fifth conference on
asphalt pavements for Southern Africa; CAPSA 89, held in Swaziland, 5-9 June 1989,
Section 8, pp 1-4
15. Bissada, A.F. 1987. Structural response of foamed-asphalt-sand mixtures in hot
environments. In: Asphalt materials and mixtures. Washington, DC: Transportation
Research Board. (Transportation Research Record, 1115), pp 134-149.
16. Bowering, R.H. & Martin, C.L. 1976. Foamed bitumen production and application of
mixtures, evaluation and performance of pavements. in: Proceedings of the Association of
Asphalt Paving Technologists, Vol. 45, pp. 453-477.
17. Bowering, R.H. 1970. Properties and behaviour of foamed bitumen mixtures for road
building. In: Proceedings of the 5th Australian Road Research Board Conference, held in
Canberra, Australia, 1970, pp. 38-57.
18. Bowering, R.H. & Martin, C.L. 1976. Performance of newly constructed full depth foamed
bitumen pavements. In: Proceedings of the 8th Australian Road Research Board
Conference, held in Perth, Australia, 1976.
19. Brennen, M., Tia, M., Altschaeffl, A.G. & Wood, L.E. 1983. Laboratory investigation of
the use of foamed asphalt for recycled bituminous pavements. In: Asphalt materials,
mixtures, construction, moisture effects and sulfur. Washington, DC: Transportation
Research Board. (Transportation Research Record; 911), pp 80-87.
20. Castedo-Franco, L.H., Beaudoin, C.C., Wood, E.L. & Altschaeffl, A.G. 1984. Durability
characteristics of foamed asphalt mixtures. In: Proceedings of the 29th Annual Canadian
Technical Asphalt Association Conference, held in Montreal, Canada, 1984.
21. Collings, D. 1997. Through foaming it's possible to mix hot asphalt with cold, damp
aggregate. Asphalt Contractor, June 1997 (Article based on the presentation at the 1997
ARRA annual meeting, San Antonio, TX).
22. Joubert, G., Poolman, S. & Strauss, P.J. 1989. Foam bitumen stabilised sand as an
alternative to gravel bases for low volume roads. In: 5th Conference on Asphalt Pavements
for South Africa (CAPSA 89), Proceedings held in Swaziland, 5-9 June, 1989, Section 8,
pp21-5.
Laboratory and Field Evaluation of Recycled Cold Mixes 110
23. Lancaster. J., McArthur, L. & Warwick, R. 1994. VICROADS experience with foamed
bitumen stabilisation. In: 17th ARRB Conference, Proceedings held in Gold Coast,
Queensland, 15-19 August, 1994, Volume 17, Part 3, pp193-211.
24. Lee, D.Y. 1981. Treating marginal aggregates and soil with foamed asphalt. In:
Proceedings of the Association of Asphalt Paving Technologists, Vol. 50, pp 211-150.
25. Little, D.N., Button, J.W. & Epps, J.A. 1983. Structural properties of laboratory mixtures
containing foamed asphalt and marginal aggregates. In: Asphalt materials, mixtures,
construction, moisture effects, and sulfur. Washington, DC: Transportation Research
Board. (Transportation Research Record; 911), pp 104-113.
26. Maccarrone, S., Holleran, G., Leonard. D.J. & Hey, S. 1994. Pavement Recycling using
Foamed Bitumen. In: 17th ARRB Conference, Proceedings held in Gold Coast,
Queensland, 15-19 August, 1994, Volume 17, Part 3, pp 349-365.
27. Maccarrone, S., Holleran, G, & Leonard, D.J. 1993. Bitumen Stabilisation - A New
Approach To Recycling Pavements. In: AAPA Members Conference, 1993.
28. Maccarrone, S., Holleran, G. & Ky, A. 1995. Cold Asphalt Systems as an Alternative to
Hot Mix. In: 9th AAPA International Asphalt Conference.
29. Roberts, F.L., Engelbrecht, J.C. & Kennedy, T.W. 1984. Evaluation of recycled mixtures
using foamed asphalt. In: Asphalt mixtures and performance. Washington, DC:
Transportation Research Board. (Transportation Research Record; 968), pp 78-85.
30. Foamix asphalt advances by Ruckel, P.J. ... [et al]. In: Asphalt Pavement Construction:
New Materials and Techniques. Philadelphia, PA: American Society for Testing and
Materials (ASTM STP; 724), pp. 93-109.
31. Ruckel, P.J., Acott, S.M. & Bowering, R.H. 1982. Foamed-asphalt paving mixtures:
preparation of design mixes and treatment of test specimens. In: Asphalt materials,
mixtures, construction, moisture effects and sulfur. Washington, DC: Transportation
Research Board. (Transportation Research Record; 911), pp 88-95.
32. Sakr, H.A. & Manke, P.G. 1985. Innovations in Oklahoma foamix design procedures. In:
Asphalt materials, mixes, construction and quality. Washingtong, DC: Transportation
Research Board. (Transportation Research Record;1034), pp 26-34.
33. Tia, M. & Wood, L.E. 1983. Use of asphalt emulsion and foamed asphalt in cold-recycled
asphalt paving mixtures. In: Low-volume roads: third international conference.
Laboratory and Field Evaluation of Recycled Cold Mixes 111
Washington, DC: Transportation Research Board. (Transportation Research Record; 898),
pp 315-322.
34. Van Wyk, A., Yoder, E.J. & Wood, L.E. 1983. Determination of structural equivalency
factors of recycled layers by using field data. In: Low-volume roads: third international
conference. Washington, DC: Transportation Research Board. (Transportation Research
Record; 898), pp 122-132.
35. Van Wijk, A.J. 1984. Structural comparison of two cold recycled pavement layers. In:
Design, evaluation, and performance of pavements. Washington, DC: Transportation
Research Board. (Transportation Research Record; 954), pp 70-77.
36. Van Wijk, A. & Wood, L.E. 1983. Use of foamed asphalt in recycling of an asphalt
pavement. In: Asphalt materials, mixtures, construction, moisture effects and sulfur.
Washington, DC: Transportation Research Board. (Transportation Research Record; 911),
pp 96-103.
37. Van Wijk. A. & Wood, L.E. 1982. Construction of a recycled pavement using foamed
asphalt. In: Proceedings of the Twenty-seventh Annual Conference of Canadian Technical
Asphalt Association, edited by P Turcotte, held in Edmonton, Alberta, Canada, 1982.
38. CAPSA'99 - van der Walt et al: The Use Of Foamed Bitumen In Full-Depth In-Place
Recycling Of Pavement Layers Illustrating The Basic Concept Of Water Saturation In The
Foam Process