Dissertation report on     “LABORATORY AND FIELD EVALUATION OF            RECYCLED COLD MIXES”               Submitted in ...
CERTIFICATEThis is to certify that the Dissertation report entitled “LABORATORY ANDFIELD EVALUATION OF RECYCLED COLD MIXES...
ACKNOLEDGEMENTSI would like to express my sincere gratitude to Dr. P.K. Nanda, Director, Central Road ResearchInstitute, N...
My Hearty Gratefulness and thanks to Dr. Pawan Saluja, Shri. Gajender Kumar, Shri ManojShukla, Dr. Sangitha and CRRI-Flexi...
ABSTRACTIn the dense populated cities like Delhi, where environmental pollution and Land fill problems areof prime concern...
CONTENTS S.NO.               TITLE                                                                                        ...
2.16.4 Saudi Arabia – A desert road for heavy traffic ............................................................. 45   2...
LIST OF FIGURESFigure 2.1: Example of fluid considerations for a bitumen emulsion stabilised material       10Figure 2.2: ...
Figure 2.27: Vogele 1800 paving the foamed bitumen treated base material directly onto theroad as an overlay              ...
Figure3.18: Specimen setup of dynamic creep testing                                         71Figure3.19: Benkelman Beam r...
Table3.17: Deflection data (RHS, towards Karnataka cold Storage Pvt. ltd)              76Table4.1: Maximum bulk density va...
_________________________________________CHAPTER 11. INTRODUCTION1.1 GeneralIn the dense populated cities like Delhi, wher...
1.2 Objectives   •   To study the suitability of cementitious and bituminous agents (Emulsion and Foamed       bitumen) fo...
_________________________________________CHAPTER 22. LITERATURE REVIEW2.1 Why Milling?Milling is the process of cutting aw...
•   Major energy savings, including those related to avoiding processing of additional virgin        material and the pote...
removal or “milling” is completed with a self propelled rotary drum cold planing machine. TheReclaimed Asphalt Pavement (R...
2.5 Advantages of Cold RecyclingCold recycling and full depth reclamation of asphalt pavements provide many environmental ...
2.6 Bitumen EmulsionBitumen emulsions, used in road construction and maintenance, may be defined as a homogeneousmixture o...
2.7 Bitumen Emulsion ClassificationBitumen emulsions are classified into three categories: anionic, cationic and nonionic....
2.8 Recycling With Bitumen EmulsionWhen recycling with bitumen emulsion the following points are important and need to bea...
than that of water. Both the bitumen and water components of an emulsion act as a lubricant inassisting compaction, so bot...
situ moisture contents are best addressed by pre-pulverising the existing pavement therebyexposing the material and allowi...
2.9 Foamed BitumenIn order to mix bitumen with road-building aggregates, you first need to considerably reduce theviscosit...
on contact with the hot bitumen, is turned into vapour which is trapped in thousands of tinybitumen bubbles. In the foam s...
Figure 2-3: Bitumen Foam characterization2.11 Factors influencing foam propertiesThe expansion ratio and half-life of foam...
Bitumen source: Some bitumens foam better than others due to their composition. For example,the foaming properties of bitu...
lower limits be recognized. Normally accepted minimum values for expansion ratio and half-lifefor stabilising material at ...
Figure 2-4: Foamed bitumen dispersion and binding in the treated mix2.13 Material suitability for foamed bitumen treatment...
Figure 2-5: Material gradation envelopsSimple laboratory gradation tests carried out on representative samples taken from ...
P = percentage by mass passing a sieve of size d (mm)       D = maximum aggregate size (mm)       F = percentage filler co...
Table2. 12: Foamed bitumen dispersion (ability to mix)Consistency of bitumen supplyWhen coupling a new tanker to the recyc...
Application of active fillerAs described above, it is standard practice to add a small amount of cement or other suchcemen...
filler Poorly graded clean sand                          2.5 to 5%        filler Silty sand                               ...
Studies have shown that foamed asphalt mixes do not develop their full strength after compactionuntil a large percentage o...
minimize the loss in stability under soaked moisture conditions. The major functions of foamedbitumen treatment are to red...
Bitumen stabilised material is normally evaluated using the Indirect Tensile Strength (ITS) inpreference to Marshall testi...
2.15 The benefits of foamed bitumen stabilisationThe following advantages of foamed asphalt are well documented:   •   The...
•   A weak granular base overlies a reasonably strong subgrade.•   A granular base too thin to consider using cementitious...
Table2.15: Comparison between different types of bitumen applicationsFactor                  Bitumen Emulsion       Foamed...
2.16 Case studies       Experience in India:2.16.1 Emulsion Cold Recycling Rehabilitation Project-HyderabadProject locatio...
•   The laid recycled layer was compacted with a 15tonne vibratory roller. Initially high    amplitude and low frequency m...
Figure2.6: A view of recycling process progress in HyderabadFigure2.7: Aggregate Spread over the layer to be recycled to c...
Figure2.8: Recycling crew in action        Figure2.9: Recycled layer after pre-compactionLaboratory and Field Evaluation o...
Figure2.10: Compacting the recycled layerFigure2.11: Tack coat application over the recycled and compacted layer   Laborat...
Figure2.12: Finished surface of the recycled layerLaboratory and Field Evaluation of Recycled Cold Mixes      34
2.16.2 Foam bitumen cold recycling rehabilitation project-BangaloreExisting Pavement              Kumbalgodu is an Industr...
•   The compaction process was started with vibratory roller and is finished with pneumatic    tyred roller to achieve spe...
Figure2.13: Loader used to load the materials in to the mobile plant     Figure2.14: Cement and hot bitumen supplied to th...
Figure2.15: Recycled material being discharged in to the dumperFigure2.16: Recycled foamix being dumped in to the paver ho...
Figure2.17: Initial compaction with vibratory roller   Figure2.18: Final compaction with pneumatic tyred rollerLaboratory ...
Experience in abroad:2.16.3 Emulsion Cold Recycling Rehabilitation Project. Citizen Court, Toronto,June 2003Existing Pavem...
Recycling Sequence of OperationPass No 1:2.5m wide, from centre line out. The total width of the pavement was 10.4m wide, ...
Figure2.19: Recycling option used          Figure 2-20: Emulsion tanker and recyclerLaboratory and Field Evaluation of Rec...
Figure 2-21: Pre-compacted surface after 1st pass         Figure 2-22: Cold milling from kerb outwardsLaboratory and Field...
Figure 2-23: Pre-compacted surface after 2nd passLaboratory and Field Evaluation of Recycled Cold Mixes     44
2.16.4 Saudi Arabia – A desert road for heavy trafficThe dual-lane Shaybah Access Road, with a total length of more than 3...
Figure 2-24: Recycling of Shaybah Access roadLaboratory and Field Evaluation of Recycled Cold Mixes   46
2.16.5 In-Plant recycling using milled asphalt bound with foamed bitumenResponsible partiesClient: Durban Municipality, Ro...
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Lab and field eveluation of recycled cold mix
Upcoming SlideShare
Loading in...5
×

Lab and field eveluation of recycled cold mix

3,266

Published on

recycled asphalt material treatment with emulsion/foamed bitumen,

Published in: Education, Technology, Business
1 Comment
0 Likes
Statistics
Notes
  • Be the first to like this

No Downloads
Views
Total Views
3,266
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
860
Comments
1
Likes
0
Embeds 0
No embeds

No notes for slide

Lab and field eveluation of recycled cold mix

  1. 1. 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 SHRI ARUN GAUR Head, Lecturer Flexible Pavements Division, Department of Civil Engineering CRRI-New Delhi MNIT-Jaipur DEPARTMENT OF CIVIL ENGINEERING MALAVIYA NATIONAL INSTITUTE OF TECHNOLOGY (DEEMED UNIVERSITY) JAIPUR (RAJASTHAN)-302017 Laboratory and Field Evaluation of Recycled Cold Mixes I
  2. 2. CERTIFICATEThis is to certify that the Dissertation report entitled “LABORATORY ANDFIELD EVALUATION OF RECYCLED COLD MIXES” being submitted byMr. G. NARENDRA GOUD (College ID -046126) to the Department of civilengineering, Malaviya National Institute of Technology-Jaipur, in partial fulfillmentfor the award of Master of Technology in Transportation Engineering is a bona fidework carried out by him under our guidance and supervision.The contents of this dissertation, in full or in parts, have not been submitted to anyother institute or university for the award of any degree or diploma.Place: New DelhiDate: / 6/ 2006 (Dr. SUNIL BOSE) (Shri ARUN GAUR) Head, Lecturer Flexible Pavements Division, Department of Civil Engineering CRRI-New Delhi MNIT-Jaipur Laboratory and Field Evaluation of Recycled Cold Mixes II
  3. 3. ACKNOLEDGEMENTSI would like to express my sincere gratitude to Dr. P.K. Nanda, Director, Central Road ResearchInstitute, New Delhi for permitting me to carryout my dissertation work in Flexible PavementsDivision, CRRI.It is most pleasant to express hearty gratitude to my external guide Dr Sunil Bose, Head flexiblepavements division-CRRI, who has given me the opportunity and under whose supervision I wasable to do my dissertation work. Words can not do much justice to the guidance and help given byhim.I sincerely express my deep gratitude to my internal guide Shri. Arun Gaur, Lecturer, Departmentof 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 PrivateLimited, for providing me all the facilities in carrying out the study. I am grateful to all theemployees of Wirtgen India Private Limited-Bangalore whoever helped me during my associationwith 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 theirproject site Bidadi-Bangalore. Laboratory and Field Evaluation of Recycled Cold Mixes III
  4. 4. My Hearty Gratefulness and thanks to Dr. Pawan Saluja, Shri. Gajender Kumar, Shri ManojShukla, 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 NationalInstitute 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, BangaloreUniversity who has accepted immediately to conduct BBD study on the test track.My special thanks to Shri. Pawan Kalla, Lecturer Department of Civil Engineering, MalaviyaNational Institute of Technology, Jaipur and Shri. Sridhar Raju, Scientist, CRRI. whoencouraged 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 givenrequired 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 ofmy dissertation work. (G. Narendra Goud) Laboratory and Field Evaluation of Recycled Cold Mixes IV
  5. 5. ABSTRACTIn the dense populated cities like Delhi, where environmental pollution and Land fill problems areof prime concerns in the recent years. In rapid developing countries like India, where conservationand optimum utilization of the road building materials specially petroleum and mineral productsare an important issue. There is an immediate attention requirement towards the development andimplementation of Ecofriendly and cost effective pavement construction technologies. Throughapplication of these technologies the efficient use of existing and waste materials can be madewith out creating problems to the environment and at the same time meeting the qualityrequirements of the pavements.Advances in technology and techniques in the in recent years have made cold recycling anincreasingly popular and cost-effective pavement construction and maintenance technique. In thepresent study an effort is made to study the laboratory and field behaviour of recycled cold mixeswith binders as an emulsion and foamed bitumen. The Marshall specimens were cast usingemulsion and foamed bitumen in combination with different types of fillers such as cement, limeand fly-ash. The specimens were tested for density, Indirect Tensile Strength, Resilient modulusand dynamic creep. Benkelman Beam deflection study was carried out on the pavementconstructed with recycled foamed bituminous mix after a period of three months from constructionand field cores were cut from the pavement and were investigated in the Laboratory. It was foundthat the pavement constructed with foamed bitumen treated RAP was structurally sound and corescut from that pavement have shown higher ITS and MR values when compared with Laboratorycast cores but they shown less creep stiffness and densities. In comparison with emulsion treatedRAP, foamed bitumen treated RAP shown higher density, ITS, MR and creep stiffness with sameaggregate and gradation. Laboratory and Field Evaluation of Recycled Cold Mixes V
  6. 6. CONTENTS S.NO. TITLE Pg NO1. INTRODUCTION...................................................................................................................... 1 1.1 General ................................................................................................................................. 1 1.2 Objectives............................................................................................................................. 2 1.3 Scope of Work ..................................................................................................................... 2 1.4 Methodology Adopted ......................................................................................................... 22. 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 VI
  7. 7. 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 .......................... 473. 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................................................................................ 764. 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............................................................................... 905. CONCLUSIONS AND RECOMMENDATIONS ...................................................................... 926. APPENDICES .......................................................................................................................... 93 Appendix 1: Material Sampling and blending ......................................................................... 93 Appendix 2: Mix Design Procedure for Bitumen Stabilised Materials ................................... 95 Appendix 3: Strength Test Procedures................................................................................... 1057. REFERENCES....................................................................................................................... 108 Laboratory and Field Evaluation of Recycled Cold Mixes VII
  8. 8. LIST OF FIGURESFigure 2.1: Example of fluid considerations for a bitumen emulsion stabilised material 10Figure 2.2: Schematic diagram of foamed bitumen production 12Figure 2.3: Bitumen Foam characterization 14Figure 2.4: Foamed bitumen dispersion and binding in the treated mix 17Figure 2.5: Material gradation envelops 18Figure 2.6: A view of recycling process progress in Hyderabad 31Figure 2.7: Aggregate Spread over the layer to be recycled to correct the Gradation 31Figure 2.8: Recycling crew in action 32Figure 2.9: Recycled layer after pre compaction 32Figure 2.10: Compacting the recycled layer 33Figure 2.11: Tack coat application over the recycled and compacted layer 33Figure 2.12: Finished surface of the recycled layer 34Figure 2.13: Loader used to load the materials in to the mobile plant 37Figure 2.14: Cement and hot bitumen supplied to the plant 37Figure 2.15: Recycled material being discharged in to the dumper 38Figure 2.16: Recycled foamix being dumped in to the paver hopper 38Figure 2.17: Initial compaction with vibrator roller 39Figure 2.18: Final compaction with pneumatic tyred roller 39Figure 2.19: Recycling option used 42Figure 2.20: Emulsion tanker and recycler 42Figure 2.21: Pre-compacted surface after 1st pass 43Figure 2.22: Cold milling from kerb outwards 44Figure 2.23: Pre-compacted surface after 2nd pass 45Figure 2.24: Recycling of Shaybah Access road 46Figure2.25: The Hartl Powercrusher PC 1270 I Impact crusher being used to crush the RAPmaterial 50Figure2.26: The Wirtgen KMA 200 cold mixing plant utilized to dose and mix the bindingagents and water with the RAP 50 Laboratory and Field Evaluation of Recycled Cold Mixes VIII
  9. 9. Figure 2.27: Vogele 1800 paving the foamed bitumen treated base material directly onto theroad as an overlay 51Figure 2.28: Compaction done with HAMM HD O70V double drum Oscillation /Vibration roller and HAMM GRW 18 pneumatic tyred roller 51Figure2.29: The road surface being moistened with water during final compaction andjust before traffic is allowed onto the base course 52Figure2.30: The longitudinal joint being moistened before paving of the second road-width52Figure 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 53Figure2.32: The finished cold recycled base course after being trafficked for several days 53Figure2.33: The Tack coat applied by a hand sprayer on one half of the base course 54Figure2.34: Paving and compaction of the 4 cm asphalt wearing course 55Figure3.1: WLB 10- Wirtgen foamed bitumen lab kit 57Figure3.2: Air pressure Influence on expansion ratio and half time of Foamed bitumen 58Figure3.3: Bitumen temperature Influence on expansion ratio and half time of Foamedbitumen 58Figure3.4: Bitumen water content Influence on expansion ratio and half life time of Foamedbitumen 59Figure3.5: option1 gradation curves 62Figure3.6: option2 gradation curves 62Figure3.7: option3 gradation curves 63Figure3. 8: option4 gradation curves 63Figure3.9: samples of separated RAP and stone dust 64Figure3.10: OMC determination 64Figure3.11: OFC determination 65Figure3.12: Mineral aggregates used in the study 66Figure3.13: WLB10 laboratory plant used to produce foamed bitumen 66Figure3.14: Pug-mill type mixer used to prepare foamix 67Figure3.15: Hobart mixer used to prepare emulsion mixture 69Figure3.16: Indirect Tensile Strength Testing Schematic diagram 70Figure3.17: Specimen setup of Indirect Tension Test for Resilient Modulus 71 Laboratory and Field Evaluation of Recycled Cold Mixes IX
  10. 10. Figure3.18: Specimen setup of dynamic creep testing 71Figure3.19: Benkelman Beam rebound deflection variation with distance 76Figure 7.1 Determination of optimum foaming water content 100 LIST OF TABLESTable2. 1: The major uses of bitumen emulsion 07Table2. 2: Bitumen emulsion classification and their recommended application.(IS 8887-2004) 08Table2. 3: Foamed bitumen dispersion (ability to mix) 20Table2. 4: Typical foamed bitumen contents relative to key aggregate fractions 21Table2. 5: Tentative binder and additional treatment requirements 22Table2.6: Comparison between different types of bitumen applications 28Table3. 1: Sieve analysis of pulverized and air-dried RAP 55Table3. 2: Sieve analysis of Stone Dust 55Table3. 3: Air pressure Influence on expansion ratio and half time of Foamed bitumen 57Table3. 4: Bitumen temperature Influence on expansion ratio and half time of Foamedbitumen 58Table3. 5: Study of Bitumen water content Influence on expansion ratio and half life timeof Foamed bitumen 58Table3. 6: Tests on Emulsion 59Table3. 7: Different options of aggregate proportions 60Table3. 8: Option1 Material proportions 60Table3.9: Option2 Material proportions 60Table3.10: Option3 Material proportions 61Table3.11: Option4 Material proportions 61Table 3.12: Material calculations for foamix preparation 68Table 3.13 Foamed bitumen Specimen test results 72Table 3.14 Bitumen Emulsion Specimen test results 74Table3.15: Dynamic Creep Test results 75Table3.16: Deflection data (LHS, towards Karnataka cold Storage Pvt. ltd) 76 Laboratory and Field Evaluation of Recycled Cold Mixes X
  11. 11. Table3.17: Deflection data (RHS, towards Karnataka cold Storage Pvt. ltd) 76Table4.1: Maximum bulk density values from the Graphs 4.1(a, b, c) 77Table 4.2: Maximum Resilient modulus (MR) values from the Graphs 4.2(a, b) 80Table4.3: Maximum Resilient modulus (MR) values from the Graphs 4.3 (a, b) 81Table4.4: Maximum Resilient modulus (MR) values from the Graphs 5.6(a, b) 82Table 4.5: Maximum Dry Indirect Tensile Strength (ITS) values from the Graphs 4.5 (a, b, c) 83Table 4.6: Maximum soaked Indirect Tensile Strength (ITS) values 83Table4. 7: Maximum bulk density values From the Graphs 4.6 (a, b) 85Table4. 8: Maximum Resilient Modulus values from the Graphs 4.7 (a, b) 86Table 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 GRAPHSGraph4. 1:( a, b, c) Variation of bulk density with foamed bitumen and filler 78Graph4.2 :( a, b) Variation of Resilient Modulus with foamed bitumen and Cement 80Graph4.3 :( a, b) Variation of Resilient Modulus with foamed bitumen and Lime 81Graph4.4 :( a, b) Variation of Resilient Modulus with foamed bitumen and Fly-ash 82Graph4.5: (a, b, c) Variation of dry ITS with foamed bitumen 84Graph4.6 :( a ,b) Variation of bulk density with Bitumen Emulsion 85Graph4.7 :( a, b) Variation of Resilient Modulus with Bitumen Emulsion 86Graph4.8: (a, b) Variation of ITS with Bitumen Emulsion and Cement 88Graph4.9 :( a, b) Variation of ITS with Bitumen Emulsion and lime 88Graph4.10 :( a, b, c) Variation of Resilient Modulus, Bulk density and ITS indifferent cores 89Graph4.12 :( a, b, c) Variation of Accumulated axial strain with Number of cycles 90Graph4.11 :( a, b) Variation of Accumulated axial strain with Number of cycles 91 Laboratory and Field Evaluation of Recycled Cold Mixes XI
  12. 12. _________________________________________CHAPTER 11. INTRODUCTION1.1 GeneralIn the dense populated cities like Delhi, where environmental pollution and Land fill problems areof prime concerns in the recent years. In rapid developing countries like India, where conservationand optimum utilization of the road building materials specially petroleum and mineral productsand energy are an important issues. The rehabilitation and up gradation of existing badlydistressed Pavements due to rapidly growing heavy vehicular traffic are attracting theconcentration. There is an immediate attention requirement towards the development andimplementation of Ecofriendly pavement construction technologies. Through application of thesetechnologies the efficient use of existing and waste materials can be made with out creatingproblems to the environment and at the same time meeting the quality requirements of thepavements.Advances in technology and techniques in the in recent years have made cold recycling anincreasingly popular and cost-effective pavement construction and maintenance technique. It hasbeen proved in abroad that cold recycling with emulsion or foamed bitumen is one of the bestalternatives to be considered as a rehabilitation option. Cold recycling technology can be an optionwhich 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 coldmixes with binders as an emulsion and foamed bitumen. The Marshall specimens were cast usingemulsion and foamed bitumen in combination with different types of fillers such as cement, limeand fly-ash. The specimens were tested for density, Indirect Tensile Strength, Resilient modulusand dynamic creep. Benkelman Beam deflection study was carried out on the pavementconstructed with recycled foamed bituminous mix after a period of three months from constructionand field cores were cut from the pavement and were investigated in the Laboratory. Laboratory and Field Evaluation of Recycled Cold Mixes 1
  13. 13. 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 mix1.3 Scope of WorkIn the present study stabilizing agents viz. cementitious and bituminous was investigated for itsuse with Recycled Asphalt Pavement (RAP) material. The effect of different stabilizing agents andtheir dosage on density, indirect tensile strength (ITS) and other performance parameters ofstabilized 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 2
  14. 14. _________________________________________CHAPTER 22. LITERATURE REVIEW2.1 Why Milling?Milling is the process of cutting away material by feeding a work piece past a rotating multipletooth cutter. It can be carried out when the pavement condition is in COLD or HOT. Cold millingis considered to be more economical, ecofriendly in nature and can be done to pavement fulldepth.Earlier roads were designed for less traffic and lighter vehicle weights than found today. Manyroads are being distorted and failing prematurely as a result. Reestablishing a uniform surface isessential if these roads are to be properly repaired. Milling provides a uniform surface for theplacement of new pavement. If rutted roads are overlaid as it is, insufficient material is placed inthe rutted area, producing low density in the areas of the ruts. By milling to a flat surface, recycledmaterial is created, the ruts are eliminated, and the new pavement will have a uniform densityacross the entire lane. Milling can reestablish the proper road grade and slope and eliminate highspots and ruts. Many times, milling can reduce or even eliminate reflective cracking. Betterleveling 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 inlayingon highway work are Shoulders do not have to be raised, Guard rails do not have to be raisedbecause the road elevation remains the same. Milling also provides utility accesses (i.e. draingullies, man holes, etc) to remain same. Bridge clearances remain the same, so clearance signs donot have to be changed.2.2 Why Recycling?Recycling:-The reuse, usually after some processing, of a material that has already served its firstintended purpose.The reasons for, and advantages from, Recycled Asphalt (RA) being put back in to pavements canbe 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 3
  15. 15. • 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 RecyclingPavement may be recycled in-place or in-plant depending on various factors such as availability ofequipment, existing material quality and requirement of the quality control over the treatedmaterial.An in-situ or in-place recycling process involves a train of machines planing out, and thenimmediately processing, the material and relaying it without removing it from site. In-siturecycling is usually preferred because it is less costly (with the elimination of costs associated thestockpiling, handling, maintaining an inventory and long distance hauling of the reclaimedmaterial) 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 (oftenfar 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 asphaltpavement recycling: i. Cold planing ii. Hot recycling iii. Hot in-place recycling iv. Cold recycling and v. Full-Depth ReclamationCold planing:- The asphalt pavement is removed to a specified depth and the surface is restored toa desired grade cross slope and free of humps, ruts and other imperfections. The pavement Laboratory and Field Evaluation of Recycled Cold Mixes 4
  16. 16. removal or “milling” is completed with a self propelled rotary drum cold planing machine. TheReclaimed Asphalt Pavement (RAP) is transferred to trucks after removal and stockpiled for hot orcold recycling.Hot recycling:-RAP is combined with new aggregate and asphalt cement and/or recycling agent toproduce Hot Mix Asphalt (HMA). Although batch type hot mix plants are used, drum plantstypically are used to produce the recycled mix. Most of the RAP is produced by cold planing butalso can be produced from pavement removal and crushing. The mix placement and compactingequipment and procedures are those typical of HMA construction.Hot In-place Recycling (HIPR): The HIPR is defined as a process to correct asphalt pavementsurface distress by softening the existing surface with heat, mechanically removing the pavementsurface, mixing the reclaimed asphalt with a recycling agent, possibly adding virgin asphalt and/oraggregate, 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 asphaltpavement typically is processes to a depth of from 50 to 100mm. the pavement is pulverized andthe reclaimed material is mixed with an Emulsion or foamed bitumen, spread and compacted toproduce a base course. Cold recycled base courses require a new asphalt surfaceFull Depth Reclamation (FDR):- With FDR, all of the pavement section, and in some cases apredetermined amount of underlying material are mixed with asphalt emulsion or Foamed bitumento produce a stabilized base course. Base problems can be corrected with this construction. FDRconsists of six basic steps: pulverization, stabilizing agent and/or emulsion or Foamed bitumenincorporation, spreading, compacting, shaping and placement of new asphalt surface. [2]2.4 Candidates for RecyclingA candidate for recycling is usually an old asphalt pavement, from HMA to an aggregate basewith surface treatment. Candidate pavement will have severe cracking and disintegration, such aspot holes. Frequently the poor condition is due to the pavement being too thin or weak for thetraffic and so it is being over stressed. Poor drainage can also accelerate the rate and amount ofpavement deterioration. All types of asphalt pavements can be recycled: low, medium and hightraffic volume highways, urban streets, airport taxi ways, runways and aprons, and parking lots.[2] Laboratory and Field Evaluation of Recycled Cold Mixes 5
  17. 17. 2.5 Advantages of Cold RecyclingCold recycling and full depth reclamation of asphalt pavements provide many environmental andother 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 6
  18. 18. 2.6 Bitumen EmulsionBitumen emulsions, used in road construction and maintenance, may be defined as a homogeneousmixture of minute Bitumen droplets suspended in a continuous water phase. These types ofemulsions are usually termed oil-in-water (o/w) emulsions. Emulsions typically contain asphaltcement, 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 mechanicaldevice, such as a colloid mill. The colloid mill breaks down molten asphalt into minute droplets inthe presence of water and a chemical, surface-active emulsifier. The emulsifier imparts itsproperties to the dispersed asphalt arid is most influential in maintaining stable asphalt dropletsuspension.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 emulsionSurface treatments Asphalt recycling Other applicationsFog sealing, Sand sealing, Cold in-place, Full depth, Hot Stabilization, MaintenanceSlurry sealing, Micro- in-place, Central plant patching, Tack coats, Primesurfacing, Cape sealing coats, Dust palliatives, Crack filling, Protective coatings Laboratory and Field Evaluation of Recycled Cold Mixes 7
  19. 19. 2.7 Bitumen Emulsion ClassificationBitumen emulsions are classified into three categories: anionic, cationic and nonionic. In practicethe 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 termsonly and mean rapid setting, medium setting, slow setting and quick setting. The tendency tocoalesce is closely related to the speed with which an emulsion will become un-stable and breakafter contacting the surface of aggregate. An RS emulsion has little or no ability to mix with anaggregate, an MS emulsion is expected to mix with coarse but not fine aggregate, and SS and QSemulsions are designed to mix with fine aggregate, with the QS expected to break more quicklythan the SS.Emulsions are further identified by a series of numbers and letters related to viscosity of theemulsions and hardness of the base bitumen. The letter “C” in front of the emulsion type denotescationic. 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, anMS-2 is more viscous than an MS-1. The “h” that fallows certain grades simply means that harderbase 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 permitsa thicker bitumen film on the aggregate particles and prevents drain off of bitumen from theaggregate. 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 Recommended application type RS-1 Tack coat applications. RS-2 Surface dressing work. Plant or road mixes with coarse aggregates minimum 80%, all of which is retained MS on 2.36mm IS Sieve, and also for surface dressing and penetration macadam. SS-1 Fog seal, Crack sealing and Prime coat applications. Plant or road mixes with graded and fine aggregates such as Cold mixes MSS, SS-2 SDBC and slurry seal. Laboratory and Field Evaluation of Recycled Cold Mixes 8
  20. 20. 2.8 Recycling With Bitumen EmulsionWhen recycling with bitumen emulsion the following points are important and need to beaddressed:Mix designAs with any form of stabilisation, a proper mix design procedure should be followed to determinethe correct application rate required to meet the strength criteria. Each material requires its ownapplication rate of bitumen emulsion to achieve optimum or desired strength.FormulationDifferent emulsifiers and additives are used in varying proportions to “tailor” an emulsion for aspecific application. In addition to determining the amount of residual bitumen suspended inwater, such tailoring is aimed at controlling the conditions under which the bitumen breaks. Sincethe 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 isto be recycled. Details of any active filler to be added in conjunction with the bitumen emulsionmust also be supplied to allow the correct formulation to be developed and tested.HandlingBitumen emulsions are susceptible to temperature and pressure. The conditions that will promotethe 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 manufacturermust know the conditions prevailing on site to allow the correct formulation, including the detailsof all pumps that will be used for transferring the emulsion between tankers and for supplying thespray bar on the recycler. Blending of anionic and cationic emulsions results in an instantaneousbreak and blockage of pumps and pipes with viscous bitumen, for example. This can be preventedby labeling and storing emulsions carefully and ensuring that distribution systems are clear ofresidue from previous use.Total fluid content conceptWhen working with bitumen emulsions, “Total Fluid Content” is used in place of MoistureContent in defining the moisture/density relationship. Maximum density is achieved at theOptimum Total Fluid Content (OTFC), which is the combined mass of moisture and bitumenemulsion in the mix. Before breaking, bitumen emulsion is a fluid with a viscosity slightly higher Laboratory and Field Evaluation of Recycled Cold Mixes 9
  21. 21. than that of water. Both the bitumen and water components of an emulsion act as a lubricant inassisting 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 materialThe example in Figure 2-1 shows the in-situ field moisture content as 2.5 % with 3.5 % bitumenemulsion 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 theOTFC, or additional compactive effort applied to achieve maximum density. If the total fluidcontent of the material approaches saturation level (as indicated by the zero air voids line), thenhydraulic pressures will develop under the roller causing the material to heave. When suchconditions arise it is impossible to compact the material. Where the in-situ field moisture contentis high (i.e. approaching the OTFC), the addition of bitumen emulsion can increase the total fluidcontent beyond the saturation point. This situation cannot be addressed by reducing the amount ofbitumen emulsion added without compromising the quality of the stabilised product. Thetemptation to add cement to the mix in order to “absorb the surplus moisture” should not beconsidered since such a practice introduces rigidity and changes the nature of the product. High in- Laboratory and Field Evaluation of Recycled Cold Mixes 10
  22. 22. situ moisture contents are best addressed by pre-pulverising the existing pavement therebyexposing the material and allowing it to dry sufficiently before stabilising.Processing timeNo specific time limit is placed on working with bitumen emulsions other than the requirement ofcompleting all processing, compacting and finishing before the emulsion breaks. When emulsionbreaks, 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 athin film of cold, viscous bitumen, making it more difficult to compact. Compaction shouldtherefore be completed before or during the emulsion breaking process.DensityThe compaction should always aim to achieve the maximum density possible under the conditionsprevailing on site (the so-called “refusal density”). A minimum density is usually specified as apercentage of the modified AASHTO density, normally between 98 and 102% for bitumenstabilised bases.Quality controlBriquettes (for strength testing) are normally manufactured from samples taken immediatelybehind the recycler. These briquettes must be made before the emulsion breaks, thereby obtainingspecimens that reflect the compacted material on the road. Often the only way that this can beachieved 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.CuringIn order to gain strength, an emulsion mix must dispel excess water, or cure. Although somematerials stabilised with bitumen emulsion may achieve their full strength within a short period oftime (one month), curing can take longer than a year with other materials. The length of thisperiod is affected by field moisture content, emulsion/aggregate interaction, local climate(temperature, precipitation and humidity) and voids in the mix. Cement addition has a significantimpact on the rate of gain of strength. This is particularly useful where traffic is to beaccommodated on a recycled layer shortly after treatment, Research, however, has shown thatadding more than 2% by mass negatively affects the fatigue properties of the stabilised layer. Forthis reason the application rate of cement is usually limited to preferably 1.5% maximum but anabsolute maximum of 2%. Laboratory and Field Evaluation of Recycled Cold Mixes 11
  23. 23. 2.9 Foamed BitumenIn order to mix bitumen with road-building aggregates, you first need to considerably reduce theviscosity of the cold hard binder. Traditionally, this was done by heating the bitumen and mixingit with heated aggregates to produce hot mix asphalt. Other methods of reducing the bitumenviscosity include dissolving the bitumen in solvents and emulsification. Prof. Csanyi came upwith the idea of introducing moisture into a stream of hot bitumen, which effects a spontaneousfoaming of the bitumen (similar to spilling water into hot oil). The potential of foamed bitumen foruse as a binder was first realised in 1956 by Dr. Ladis H. Csanyi, at the Engineering ExperimentStation in Iowa State University. Since then, foamed asphalt technology has been usedsuccessfully in many countries, with corresponding evolution of the original bitumen foamingprocess as experience was gained in its use. The original process consisted of injecting steam intohot bitumen. The steam foaming system was very convenient for asphalt plants where steam wasreadily available but it proved to be impractical for in situ foaming operations, because of the needfor special equipment such as steam boilers. In 1968, Mobil Oil Australia, which had acquired thepatent rights for Csanyi’s invention, modified the original process by adding cold water rather thansteam into the hot bitumen. The bitumen foaming process thus became much more practical andeconomical for general use.[4] Figure 2-2 schematic diagram of foamed bitumen productionThe foamed bitumen, or expanded bitumen, is produced by a process in which pressurized waterand compressed air is injected into the hot bitumen (155-180 0c), resulting in spontaneousfoaming. The physical properties of the bitumen are temporarily altered when the injected water, Laboratory and Field Evaluation of Recycled Cold Mixes 12
  24. 24. on contact with the hot bitumen, is turned into vapour which is trapped in thousands of tinybitumen bubbles. In the foam state the bitumen has a very large surface area and extremely lowviscosity making it ideal for mixing with aggregates however the foam dissipates in less than aminute 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 distinctdifference between foamed asphalt mixes and conventional asphalt stabilised mixes is the way inwhich the bitumen is dispersed through the aggregate. In the later case the bitumen tends to coatall particles whilst in the foamed mixes the larger particles are not fully coated. The foamedbitumen 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 BitumenFoamed 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 13
  25. 25. Figure 2-3: Bitumen Foam characterization2.11 Factors influencing foam propertiesThe expansion ratio and half-life of foamed bitumen is influenced by:Water addition: Increasing the amount of water injected into the bitumen effectively increases thevolume of foam produced by a 1500 times multiplier. Thus, increasing the amount of waterincreases 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 surroundingbitumen, making it less stable and resulting in a reduction in half-life. Hence, the expansion ratioand 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 forfoaming, although harder bitumens that meet the minimum foaming requirements (explainedbelow) have been successfully used in the past. For practical reasons, harder bitumens aregenerally avoided as they produce poorer quality foam, leading to poorer dispersion. Laboratory and Field Evaluation of Recycled Cold Mixes 14
  26. 26. 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 biggerthe size of bubble that will form when the water changes state in the foaming process. Since thisprocess draws heat energy from the bitumen, the temperature before foaming needs to exceed 160ºC to achieve a satisfactory product.Bitumen and water pressure: Bitumen and water are injected into the expansion chamber throughsmall diameter openings. Increasing the pressure in the supply lines causes the flow through theseopenings to disperse (atomize). The smaller the individual particles, the larger the contact areaavailable, thereby improving the uniformity of the foam;Additives: There are numerous proprietary products on the market that will affect the foamingproperties of bitumen, both negatively (anti-foaming agents) and positively (foamants). Foamantsare usually only required where bitumen has been treated with an anti-foaming agent (normallyduring refining process). Most foamants are added to the bitumen prior to heating to applicationtemperatures and tend to be heat-sensitive; implying that their effect is short lived. To reap thebenefits 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 toimproving the foaming properties of stubborn bitumen. (Cutting back the bitumen with diesel oilhas proved successful in reducing the viscosity of the bitumen sufficiently to achieve acceptablefoam. However, this is not recommended unless carried out by the bitumen supplier.)Acceptable foaming characteristicsThe bitumen intended to be used for foaming should be tested in the laboratory to determine thefoaming characteristics. The objective of this exercise is to find that combination of water additionand bitumen temperature at which the optimal foam (highest Expansion Ratio and Half-Life) isachieved. As described above, every bitumen is different and even different batches of bitumenfrom the same source will vary. However, by following the simple laboratory procedure, the waterapplication and bitumen temperature is determined for each bitumen and these are then used onsite for full-scale foamed bitumen stabilisation. There are no upper limits to foamingcharacteristics 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 15
  27. 27. lower limits be recognized. Normally accepted minimum values for expansion ratio and half-lifefor 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 possiblewhen 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 materialtemperatures. During his research into foamed bitumen during the late 1990s, Prof. Jenkinsdeveloped 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 Ratioagainst Half-life, concluding that the better the foaming properties, the greater the Foam Index andthe better the stabilised product achieved. His research went on to compare the effect of FoamIndex with the temperature of the material at the time of mixing, concluding that as thetemperature of material increases, a lower Foam Index can be used to achieve effectivestabilization.[7]2.12 Dispersion of foamed bitumenUnlike hot-mix asphalt, material stabilised with foamed bitumen does not appear black. Thisresults from the coarser particles of aggregate not being coated with bitumen. When foamedbitumen comes into contact with aggregate, the bitumen bubbles burst into millions of tinybitumen droplets that seek out and adhere to the fine particles, specifically the fraction smallerthan 0.075 mm. The bitumen droplets can exchange heat only with the filler fraction and still havesufficiently low viscosity to coat the particles. The foamed mix results in a bitumen-bound fillerthat acts as a mortar between the coarse particles, as shown previously in Figure 4.1. There istherefore only a slight darkening in the color of the material after treatment. The addition ofcement, lime or other such fine cementitious material (100 % passing the 0.075 mm sieve) assiststhe bitumen to disperse, in particular where the recycled material is deficient in fines. Laboratory and Field Evaluation of Recycled Cold Mixes 16
  28. 28. Figure 2-4: Foamed bitumen dispersion and binding in the treated mix2.13 Material suitability for foamed bitumen treatmentThe 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. Itis important, however, to establish the boundaries of aggregate acceptability, as well as to identifythe optimal aggregate composition for foamed bitumen mix production. Material that is deficientin fines will not mix well with foamed bitumen. As depicted in Figure 4.11, the minimumrequirement 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 stringersvary in size according to the fines deficiency, a large deficiency will result in many large stringerswhich 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 17
  29. 29. Figure 2-5: Material gradation envelopsSimple laboratory gradation tests carried out on representative samples taken from the existingroad will indicate any potential deficiency in the fines content. This can be rectified by importing asuitable fine material and spreading on the road surface prior to recycling. Cohesive materialsshould, however, be treated with care as standard laboratory gradings will indicate a highpercentage passing the 0.075 mm sieve, whilst in the field the quality of mixing is often poor. Thisis due to the cohesive nature of the material causing the fines to bind together, thereby makingthem unavailable to disperse the foamed bitumen. Comparison of washed and unwashed gradingtests carried out in the laboratory will indicate the likelihood of this problem developing, theunwashed grading giving an indication of the available fines. Material that is deficient in fines canbe improved by the addition of cement, lime or other such material with 100 % passing the 0.075mm sieve. However, the use of cement in excess of 1.5 % by mass should be avoided due to thenegative effect on the flexibility of the stabilised layer. The envelopes provided in Figure 2.5 arebroad and can be refined by targeting a grading that provides the lowest voids in the mineralaggregate. This produces foamed bitumen mixes with the most desirable mix properties. A uniquerelationship 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 amixture. 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 18
  30. 30. 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 properdispersion of the foamed bitumen and easier compaction, thereby reducing voids and thematerial’s susceptibility to water ingress. Where necessary, therefore, consideration should begiven to blending two materials to improve the critical grading characteristics.2.14 Recycling with foamed bitumenPoints to be considered while treating with Foamed bitumenMaterial temperatureAggregate temperature is one of the primary factors influencing the successful dispersion offoamed bitumen and, consequently, the strength achieved in the new pavement layer. Asmentioned above, the Foam Index concept developed by Prof. Jenkins represents the combinedfoaming properties of bitumen (expansion ratio and half-life). His research finding showed that theFoam Index and aggregate temperature (at the time of mixing) were important factors in thedispersion achieved. Higher Foam Indices (i.e. better expansion and half-life) are necessary forachieving a satisfactory mix at lower temperatures. Although the implications of these findings aresignificant, it is important to compare laboratory conditions to those encountered in the field. Thequality of foam produced by a laboratory unit is always inferior to that produced by a largerecycler, the major reasons being higher working pressures in the field and continuity of operationallowing the system to function at higher temperatures. There is therefore a shift betweenlaboratory and field measurements and, for this reason, it is important to check the foamingproperties in the field. These measurements should then be compared with the temperature of theaggregate (not the road surface) and the results checked with the guidelines in Table. When thetemperature of the aggregate drops below 10 °C, foamed bitumen treatment should not beconsidered. Laboratory and Field Evaluation of Recycled Cold Mixes 19
  31. 31. Table2. 12: Foamed bitumen dispersion (ability to mix)Consistency of bitumen supplyWhen coupling a new tanker to the recycler, two basic checks should be conducted to ensure thatthe 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 shouldbe delayed until at least 100 liters of bitumen has passed through the spraybar whilst recycling inorder to obtain a truly representative sample.Bitumen flowBitumen delivered to site by tankers that are fitted with fire-heated flues is sometimescontaminated 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 therecycler’s system and can cause blockages. This problem is easily resolved by ensuring theeffectiveness of the filter in the delivery line. Any unusual increase in pressure will indicate thatthe filter requires cleaning, a procedure that should anyway be undertaken on a regular basis (e.g.at the end of every shift).Bitumen pressureThe quality of foam is a function of bitumen operating pressure. The higher the pressure, the morethe stream of bitumen will tend to “atomise” as it passes through the jet into the expansionchamber. This ensures that small bitumen particles will come in contact with the water thatsimilarly enters the expansion chamber in an atomised form, thereby promoting uniformity offoam. If the bitumen were to enter the expansion chamber as a stream (as it does under lowpressures) the water would impact on only one side of the stream, creating foam, but the other sidewould remain as unfoamed hot bitumen. It is therefore imperative to maintain a minimumoperating pressure above 3 bars. Laboratory and Field Evaluation of Recycled Cold Mixes 20
  32. 32. Application of active fillerAs described above, it is standard practice to add a small amount of cement or other suchcementitious stabilising agent when recycling with foamed bitumen. Care should be taken whenpre-treating with cement since the hydration process commences as soon as the dry powder comesinto contact with moisture, binding the fines and effectively reducing the 0.075 mm fraction. Thequality of the mix when foamed bitumen is subsequently added will be poor due to insufficientfines being available to disperse the bitumen particles. Cement should therefore always be addedin conjunction with the foamed bitumen. Table2. 13: Typical foamed bitumen contents relative to key aggregate fractions Percent passing Foamed bitumen content, % 4.75 mm 0.075 mm 3–5 3 5 – 7.5 3.5 < 50 (Gravel) 7.5 – 10 4 > 10 4.5 3–5 3.5 5 – 7.5 4 > 50 (Sands) 7.5 – 10 4.5 > 10 5 Table2. 14: Tentative binder and additional treatment requirements Material type Optimum range of Additional requirements binder Well graded clean gravel 2 to 2.5% Well graded marginally clayey/silty 2 to 4.5% gravel 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 21
  33. 33. 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 modificationMoisture ConditionsThe moisture content during mixing and compaction is considered by many researchers to be themost important mix design criteria for foamed asphalt mixes. Moisture is required to soften andbreakdown agglomerations in the aggregates, to aid in bitumen dispersion during mixing and forfield compaction. Insufficient water reduces the workability of the mix and results in inadequatedispersion of the binder, while too much water lengthens the curing time, reduces the strength anddensity of the compacted mix and may reduce the coating of the aggregates. The optimummoisture content (OMC) varies, depending on the mix property that is being optimized (strength,density, water absorption, swelling). However, since moisture is critical for mixing andcompaction, 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 “fluffpoint” of the aggregate, i.e. the moisture content at which the aggregates have a maximum loosebulk volume (70 % - 80 % mod AASHTO OMC) . However, the fluff point may be too low toensure adequate mixing (foam dispersion) and compaction, especially for finer materials. Theoptimum mixing moisture content occurs in the range of 65 - 85 per cent of the modifiedAASHTO OMC for the aggregates. The concept of optimum fluid content as used in granularemulsion mixes may also be relevant to foamed asphalt. This concept considers the lubricatingaction of the binder in addition to that of the moisture. Thus the actual moisture content of the mixfor optimum compaction is reduced in proportion to the amount of binder incorporated. The bestcompactive moisture condition occurs when the total fluid content (moisture + bitumen) isapproximately equal to the OMC. [4]Processing timeNo specific time limit is placed on working with foamed bitumen. Provided the moisture contentof the material is maintained close to the optimum moisture content, the working period can beextended.Curing Conditions Laboratory and Field Evaluation of Recycled Cold Mixes 22
  34. 34. Studies have shown that foamed asphalt mixes do not develop their full strength after compactionuntil a large percentage of the mixing moisture is lost. This process is termed curing. Curing is theprocess whereby the foamed asphalt gradually gains strength over time accompanied by areduction in the moisture content. A laboratory mix design procedure would need to simulate thefield curing process in order to correlate the properties of laboratory- prepared mixes with those offield mixes. Since the curing of foamed asphalt mixes in the field occurs over several months, it isimpractical to reproduce actual field curing conditions in the laboratory. An accelerated laboratorycuring procedure is required, in which the strength gain characteristics can be correlated with fieldbehaviour, especially with the early, intermediate and ultimate strengths attained. Thischaracterization is especially important and required when structural capacity analysis is based onlaboratory-measured strength values. Most of the previous investigations have adopted thelaboratory curing procedure proposed by Bowering (1970), i.e. 3 days oven curing at a temperatureof 60° C. This procedure results in the moisture content stabilizing at about 0 to 4 per cent, whichrepresents the driest state achievable in the field. In the present study the specimen are cured for 72hours at 40 0C temperature only.DensityGenerally density increases to a maximum and decreases as the binder content of a foamed asphaltmix increases. The strength of foamed asphalt mixes depends to a large extent on the density ofthe compacted mix. Compaction should always aim to achieve the maximum density possibleunder the conditions prevailing on site (the so-called “refusal density”). A minimum density isusually specified as a percentage of the modified AASHTO density, normally between 98 % and102 % for foamed bitumen stabilised bases. A density gradient is sometimes permitted byspecifying an “average” density. This means that the density at the top of the layer may be higherthan at the bottom. Where specified, it is normal also to include a maximum deviation of 2% forthe density measured in the lowest one-third thickness of the layer. Hence, if the average densityspecified is 100%, then the density at the bottom of the layer must be more then 98 %. For betterquality aggregates (e.g. CBR > 80 %) it is advisable to use an absolute density specification suchas Bulk Relative Density or Apparent Relative Density of the aggregate.Engineering PropertiesThe 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 commonmethod used in the selection of the design binder content was to optimize the Marshall stability and Laboratory and Field Evaluation of Recycled Cold Mixes 23
  35. 35. minimize the loss in stability under soaked moisture conditions. The major functions of foamedbitumen treatment are to reduce the moisture susceptibility, to increase fatigue resistance and toincrease the cohesion of the untreated aggregate to acceptable levels. The design foamed bitumencontent could also be selected as the minimum (not necessarily optimum) amount of binder whichwould result in a suitable mix.Moisture SusceptibilityThe strength characteristics of foamed asphalt mixes are highly moisture-dependent at low bindercontents. Additives such as lime or Cement reduced the moisture susceptibility of the mixes.Higher bitumen contents also reduce moisture susceptibility because higher densities areachievable, leading to lower permeabilities (lower void contents), and to increased coating of themoisture-sensitive fines with binder. The moisture susceptibility of the material is usuallydetermined in terms of the Tensile Strength Retained (TSR) by 100 mm briquettes, using belowequation.Temperature SusceptibilityFoamed asphalt mixes are not as temperature-susceptible as hot-mix asphalt, although both thetensile 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 equivalenthot-mix asphalt mixes after 21 days’ curing at ambient temperatures. In foamed asphalt, since thelarger aggregates are not coated with binder, the friction between the aggregates is maintained athigher temperatures. However the stability and viscosity of the bitumen-fines mortar will decreaseat high temperatures, thus accounting for the loss in strength.Unconfined Compressive Strength (UCS) and Tensile StrengthBowering (1970) suggested the following UCS criteria for foamed asphalt mixes used as a basecourses under thin surface treatments (seals): 0.5 MPa (4 day soaked) and 0.7 MPa (3 day cured at60° C). Bowering and Martin (1976) suggested that in practice the UCS of foamed asphaltmaterials usually lie in the range 1.8 MPa to 5.4 MPa and estimated that the tensile strengths offoamed 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 24
  36. 36. Bitumen stabilised material is normally evaluated using the Indirect Tensile Strength (ITS) inpreference 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 TensileStrengths of 100 kPa when tested in a soaked state and 200 kPa when tested dry.Stiffness - Resilient ModulusAs with all viscoelastic bituminous materials, the stiffness of foamed asphalt depends on theloading rate, stress level and temperature. Generally, stiffness has been shown to increase as thefines content increases. In many cases the resilient moduli of foamed asphalt mixes have beenshown 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, withthe added advantages of flexibility and fatigue resistance.Abrasion ResistanceFoamed asphalt mixes usually lack resistance to abrasion and ravelling and are not suitable forwearing/friction course applications.Fatigue ResistanceFatigue resistance is an important factor in determining the structural capacity of foamed asphaltpavement layers. Foamed asphalt mixes have mechanical characteristics that fall between those ofa granular structure and those of a cemented structure. Bissada (1987) considers that the fatiguecharacteristics of foamed asphalt will thus be inferior to those of hot-mix asphalt materials. Little etal (1983) provided evidence of this when he showed that certain foamed asphalt mixes exhibitedfatigue responses inferior to those of conventional hot-mix asphalt or high quality granularemulsion mixes. Laboratory and Field Evaluation of Recycled Cold Mixes 25
  37. 37. 2.15 The benefits of foamed bitumen stabilisationThe 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 26
  38. 38. • 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 27
  39. 39. Table2.15: Comparison between different types of bitumen applicationsFactor Bitumen Emulsion Foamed Bitumen Hot Mix AsphaltAggregate types Crushed rock Crushed rock Crushed rockapplicable Natural gravel Natural gravel 0 to 50% RAP RAP, Cold mix RAP, stabilised RAP, stabilised Marginal (Sands)Bitumen Mixing 20 0C to 70 0C 160 0C to 180 0C 140 0C to 180 0CTemperature (Before foaming)Aggregate Ambient (cold) Ambient (cold) Hot onlytemperature during (140 0C to 200 0C)mixingMoisture content 90% of OMC minus Below OMC Dryduring mixing 50% of emulsion (e.g 65% to 95% of content OMC)Type of coating of Partial coating of Coating of fine Coating of allaggregate coarse particles and particles only with aggregate particles cohesion of mix with “spot welding” of mix with controlled film bitumen / fines mortar from the bitumen / thickness fines mortarConstruction and Ambient Ambient 140 0C to 160 0CcompactiontemperatureRate of initial strength Slow Medium FastgainModification of Yes Unsuitable YesbinderImportant parameters Emulsion type Half life Penetrationof binder Residual bitumen Expansion ratio Softening point Breaking time Viscosity Curing Laboratory and Field Evaluation of Recycled Cold Mixes 28
  40. 40. 2.16 Case studies Experience in India:2.16.1 Emulsion Cold Recycling Rehabilitation Project-HyderabadProject 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 operationRoad details Width of the road: 14m Length of the road: 400m Depth of the recycled layer: 120mmMaterial 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 29
  41. 41. • 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 30
  42. 42. Figure2.6: A view of recycling process progress in HyderabadFigure2.7: Aggregate Spread over the layer to be recycled to correct the Gradation Laboratory and Field Evaluation of Recycled Cold Mixes 31
  43. 43. Figure2.8: Recycling crew in action Figure2.9: Recycled layer after pre-compactionLaboratory and Field Evaluation of Recycled Cold Mixes 32
  44. 44. Figure2.10: Compacting the recycled layerFigure2.11: Tack coat application over the recycled and compacted layer Laboratory and Field Evaluation of Recycled Cold Mixes 33
  45. 45. Figure2.12: Finished surface of the recycled layerLaboratory and Field Evaluation of Recycled Cold Mixes 34
  46. 46. 2.16.2 Foam bitumen cold recycling rehabilitation project-BangaloreExisting 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 RecyclingProject 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: 100mmMaterial 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 mixConstruction: • 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 35
  47. 47. • 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 36
  48. 48. Figure2.13: Loader used to load the materials in to the mobile plant Figure2.14: Cement and hot bitumen supplied to the plantLaboratory and Field Evaluation of Recycled Cold Mixes 37
  49. 49. Figure2.15: Recycled material being discharged in to the dumperFigure2.16: Recycled foamix being dumped in to the paver hopperLaboratory and Field Evaluation of Recycled Cold Mixes 38
  50. 50. Figure2.17: Initial compaction with vibratory roller Figure2.18: Final compaction with pneumatic tyred rollerLaboratory and Field Evaluation of Recycled Cold Mixes 39
  51. 51. Experience in abroad:2.16.3 Emulsion Cold Recycling Rehabilitation Project. Citizen Court, Toronto,June 2003Existing 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 operationDesign Mix: Depth of cutting 80 mm Grindings 98.40% Emulsion 1.60% Water Added 2.90% and Finish Course 40 mm Asphalt concreteRecycling 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 40
  52. 52. Recycling Sequence of OperationPass No 1:2.5m wide, from centre line out. The total width of the pavement was 10.4m wide, 5.2m halfwidth. 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 80mmdepth 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 withemulsion. Total recycled width after 2 passes 5.2mScreed 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 2200CRcutter width plus the pre milled section. The left hand screed width is set to 1.25m width, to matchhalf the 2200CR cutter width. Right hand screed section set to pave up to kerb edge. Total screedwidth 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 41
  53. 53. Figure2.19: Recycling option used Figure 2-20: Emulsion tanker and recyclerLaboratory and Field Evaluation of Recycled Cold Mixes 42
  54. 54. Figure 2-21: Pre-compacted surface after 1st pass Figure 2-22: Cold milling from kerb outwardsLaboratory and Field Evaluation of Recycled Cold Mixes 43
  55. 55. Figure 2-23: Pre-compacted surface after 2nd passLaboratory and Field Evaluation of Recycled Cold Mixes 44
  56. 56. 2.16.4 Saudi Arabia – A desert road for heavy trafficThe dual-lane Shaybah Access Road, with a total length of more than 380 km, leads from theBatha main route to the Saudi Aramco Shaybah area in the Rub Al Khali desert. The constructionof a reliable traffic route was imperative for the development of an oil field with affiliatedrefinery, and for the heavy-duty traffic to be expected in connection with the transport ofcomponents for the processing plant weighing up to 200 t. Originally built from Marl as anunbound gravel road only, the total length of the Shaybah Access Road was therefore recycledwithin 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 inoperation on site. With the addition of 5% foamed bitumen and 2% cement slurry, a daily averageof approximately 35,000 m2 of existing pavement could be scarified and recycled with the bindingagents down to a depth of 20 cm. In order to optimise the workability and compaction propertiesof 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 vibratingrollers and pneumatic tired rollers were employed to profile and compact the treated material. Inorder to ensure an optimum work pattern and to achieve the highest possible quality, two recyclingtrains worked staggered behind one another, thus ensuring good adhesion between the individualmachine passes and an optimum profiling of the complete lane. This also enabled the heavy-dutytraffic 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 recycledbase layer. In an inspection report, road construction experts praised the good suitability of foamedbitumen as a stabilising agent even under these extreme climatic conditions, as well as its higheconomic efficiency. The original plans involving conventional construction methods withimported crushed aggregate and hot mix asphalt had been rejected as these would have met neitherthe economical nor the time frame of this project. Figure 2-24 shows one of the three Wirtgenrecycling trains consisting of a WR 2500 and a Slurry Mixer WM 400 during the economicalrehabilitation of the Shaybah Access Road, In operation 24 hours a day despite extreme climaticconditions. Laboratory and Field Evaluation of Recycled Cold Mixes 45
  57. 57. Figure 2-24: Recycling of Shaybah Access roadLaboratory and Field Evaluation of Recycled Cold Mixes 46
  58. 58. 2.16.5 In-Plant recycling using milled asphalt bound with foamed bitumenResponsible partiesClient: Durban Municipality, Roads Department - City Engineers UnitContractor: Milling TechniksDesign Engineers: Siyenza Engineers / Loudon InternationalEquipment suppliers: Wirtgen South Africa with Wirtgen GmbH (Germany)IntroductionThe Newlands West Drive, which serves as a mayor bus route and arterial to a large residentialarea, showed signs of distress in the form of cracking of the existing asphalt layers. Therehabilitation design called for an overlay on to the existing road of 125 mm thick foamed bitumenstabilised RAP and 40 mm asphalt surfacing. The alternative conventional rehabilitation methodwith the same structural capacity would have been to overlay the existing road with an 100 mmasphalt binder layer and a 40 mm asphalt surfacing. Due to the increasing volume of stockpiledRAP at the municipal depots and the relatively low stabilising agent contents required, thealternative using the in-plant recycling method showed a significant saving for the client. Thisproject coincided with the 22nd PIARC World Road Congress. Thanks to the future orientatedthinking of the Durban Municipality, an agreement was reached together with Milling Techniksand Wirtgen South Africa to showcase the in-plant recycling and foamed bitumen technology tothe international road construction industry attending the congress during the week of 20 . 24October 2003. Laboratory and Field Evaluation of Recycled Cold Mixes 47

×