Lab and field eveluation of recycled cold mix
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recycled asphalt material treatment with emulsion/foamed bitumen,

recycled asphalt material treatment with emulsion/foamed bitumen,

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Lab and field eveluation of recycled cold mix Lab and field eveluation of recycled cold mix Document Transcript

  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • _________________________________________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
  • 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
  • _________________________________________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
  • • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • • 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
  • 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
  • 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
  • • 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
  • 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
  • Figure2.8: Recycling crew in action Figure2.9: Recycled layer after pre-compactionLaboratory and Field Evaluation of Recycled Cold Mixes 32
  • 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
  • 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 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
  • • 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
  • 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
  • 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
  • Figure2.17: Initial compaction with vibratory roller Figure2.18: Final compaction with pneumatic tyred rollerLaboratory and Field Evaluation of Recycled Cold Mixes 39
  • 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
  • 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
  • Figure2.19: Recycling option used Figure 2-20: Emulsion tanker and recyclerLaboratory and Field Evaluation of Recycled Cold Mixes 42
  • 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
  • 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 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
  • 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, 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
  • Project details Length of road: 1000 m, Width of road: 8 m Aggregate: Reclaimed Asphalt Pavement (RAP) collected from various milling contracts and stockpiled at the Durban City council’s depot. Stabilising agents: 2 % Foamed bitumen (80/100 penetration grade) and 1 % cement (OPC)Equipment utilized RAP sizing plant: Hartl PC 1270 I (Impact crusher) Mixing Plant: Wirtgen KMA 200 Paving unit: Vögele Super 1800 Compactors: HAMM HD O70V double smooth drum with one Vibratory and one Oscillation drum; and HAMM GRW 18 (pneumatic tyred roller)Technical information Design Life: 20 years Structural capacity: 4,8 million ESALs (80 kN = 8 ton) Mix properties: Indirect Tensile Strength (150 dia. briquette) > 150 KPa Retained strength > 90 % Unconfined Compressive Strength > 1500 KPa Compaction: > 100 % of modified AASHTO density (1984 kg/m³) Laboratory and Field Evaluation of Recycled Cold Mixes 48
  • Construction MethodA Hartl Power crusher PC 1270 impact crusher, was used to break down the oversized particleswithin the RAP so that 100 % of the RAP could be utilized. This crushed material was then loadedinto the hopper of the Wirtgen KMA 200 by means of a Payloader. The KMA 200 cold mixingplant was used to add the binding agents, being 2 % foamed bitumen, 1 % cement. In addition1,5% to 2,0% water was added to achieve 90 % of the optimum moisture content. The cold mixedmaterial exiting out of the KMA 200 is loaded directly onto tip trucks and transported toNewlands West drive, approximately 8 km away from the mixing plant area. The cold processedmaterial was then placed with a Vögele 1800 road paver. The TV screed on the paver equippedwith Tampers and Vibration achieved a very high degree of compaction. The layer thicknessdirectly behind the paving screed was 150 mm. To achieve the specified compaction (greater than100 % of modified Proctor density) the rollers merely had to compact the material to a thicknessof 125 mm. The compaction was achieved with a HAMM HD 70 Oscillation tandem roller and aHAMM GRW 18 pneumatic tyred roller. During final compaction a light spray of water wasapplied. This resulted in a tight knit surface, which was resistant to the wear and tear of the traffic.The foamed bitumen bound layer was trafficked immediately after final compaction wascompleted. Before the second half was paved, the transverse tie-in joint was cut by means of agrader. An alternative method of creating this tie-in joint would be by means of a W 350 millingmachine. The longitudinal joint was moistened by means of a water hosepipe and a water tanker. Itis the nature of the foamed bitumen material to be workable, even after many hours or even weeksafter mixing. Therefore the main advantages of using this cold treated material are that the layercan be trafficking directly after compaction has been completed and because the entire process is acold process the cold joints merely need to be moistened to achieve good bonding. If thetransverse day joints and longitudinal construction joints are constructed as described, they are assound as the rest of the pavement. This is due to the nature of the foamed bitumen treated material,i.e. bitumen rich mortar binding together the entire granular matrix, and the fact that particleinterlock is achieved. The finished cold recycled base course lay open without a wearing coursebetween 6 and 9 days, depending on the section. After this period a tack coat, using a stable 60bitumen emulsion, was applied before a 4 cm Asphalt wearing course was paved. Laboratory and Field Evaluation of Recycled Cold Mixes 49
  • Figure2-25: The Hartl Powercrusher PC 1270 I Impact crusher being used to crush the RAP material.Figure2-26: The Wirtgen KMA 200 cold mixing plant utilized to dose and mix the binding agents and water with the RAP. Laboratory and Field Evaluation of Recycled Cold Mixes 50
  • Figure 2-27: Vögele 1800 paving the foamed bitumen treated base material directly onto the road as an overlay .Figure 2-28: Compaction done with HAMM HD O70V double drum Oscillation / Vibration roller and HAMM GRW 18 pneumatic tyred roller. Laboratory and Field Evaluation of Recycled Cold Mixes 51
  • Figure2-29: The road surface being moistened with water during final compaction and just before traffic is allowed onto the base course. Figure2-30: The longitudinal joint being moistened before paving of the second road-width. Laboratory and Field Evaluation of Recycled Cold Mixes 52
  • Figure 2-31: Paving of the second road width and traffic on the freshly compacted material. This layer was kept moist for the first couple of hours for curing purposes. Figure2-32: The finished cold recycled base course after being trafficked for several days. Laboratory and Field Evaluation of Recycled Cold Mixes 53
  • Figure2-33: The Tack coat applied by a hand sprayer on one half of the base course. Figure2-34: Paving and compaction of the 4 cm asphalt wearing course. Laboratory and Field Evaluation of Recycled Cold Mixes 54
  • _________________________________________CHAPTER 33. LABORATORY AND FIELD STUDY3.1 RAP and Mineral Aggregate EvaluationRepresentative sample of pulverized and air dried Reclaimed Asphalt Product (RAP) and Crusherstone dust were collected from stock pile and then sieved through a set of sieves for gradation. Thedetails of sieve analysis are presented in tables 3.1 and 3.2. Bitumen content and moisture contentof air dried RAP found to be 5.2% and 0.12% respectively. Moisture content and specific gravityof air dried Stone Dust found to be 0.40% and 2.68 respectively. Mineral fillers used in the presentstudy are hydrated lime of specific gravity 2.53, Ordinary Portland cement of 53-grade and Fly-ash of specific gravity 2.12 (P-75µ=100%).Table3. 7: Sieve analysis of pulverized and air-dried RAPsieve size, 37.5 26.5 19 13.2 9.5 6.7 4.75 2.36 1.18 0.6 0.425 0.3 0.075 pan mmcumulative 100.0 99.2 95.0 74.7 52.1 39.1 29.1 16.6 7.5 5.3 3.4 2.0 0.2 0.0% passingTable3. 8: Sieve analysis of Stone Dust sieve size, mm 6.7 4.75 2.36 1.18 0.6 0.425 0.3 0.075 pan cumulative % passing 100.00 93.40 72.00 50.60 43.60 35.80 26.20 9.00 0.003.2 Foamed Bitumen CharacterizationThe Study of foamed bitumen and its characterization wais carried out using Wirtgen Foambitumen Laboratory plant, WLB-10 (Figure 3.1). The Foamability and the variation of foamcharacteristics viz. expansion ratio and half life time were observed at different air pressures,temperatures and Bitumen water contents. Dip stick and stop watch were used to find foamvolume and half life. The height of foamed bitumen immediately after complete spray and aftercomplete foam collapse was found to determine the Expansion ratio. The discharging capacity ofbitumen pump found to be 125 grams/second and the injection time of foam adopted was5seconds. The bitumen used was of 80/100 penetration grade. The graphs (figures 3.2, 3.3 and 3.3)were plotted to determine the optimum foam producing air pressure, bitumen temperature, andbitumen water content.Study of Air pressure Influence on expansion ratio and half time of Foamed bitumen:The Bitumen water, 3% (i.e. Bitumen water discharge, 10.8 l/h) and Bitumen temperature, 165 0cwere kept constant and the air pressure was varied from 3 to 6 bars at an interval of 1 bar to study Laboratory and Field Evaluation of Recycled Cold Mixes 55
  • the influence of air pressure. The bitumen water pressure was kept 1 bar more than the air pressureas given in WLB-10 operation manual. Basic height of bitumen of 625 g per unit area of containerwas found to be 1.2 cms after complete collapse of the foam. The graph plotted keeping airpressure on X-axis and expansion ratio and half life were kept on Y-axis. From this study andlooking in to the figure 3.2 optimum Air pressure was decided as (3.85+4.8)/2 =4.325 bars,fallowing the Minimum acceptable Bitumen foam parameters Expansion ratio 8 times and Half-life time 6 seconds.Study of Bitumen temperature Influence on expansion ratio and half time of Foamed bitumenThe Bitumen water, 3% (i.e. Bitumen water discharge, 10.8 l/h), Air pressure, 4.3 bars andBitumen water pressure, 5.3 bars were kept constant and Bitumen temperature was varied from150 to 180 o C at an interval of 10 0C to study the variation of expansion ratio and half life time.The graph plotted keeping Bitumen temperature on X-axis and expansion ratio and half life werekept on Y-axis. From this study and looking in to the figure 3.3 optimum bitumen temperature wasdecided as (154+156)/2 = 155 0CStudy of Bitumen water content Influence on expansion ratio and half life time of Foamed bitumenThe Air pressure, 4.3 bars, Bitumen water pressure, 5.3 bars and Bitumen temperature, 155 0Cwere kept constant and Bitumen water content was varied from 8 to 15 liters per hour to study thevariation of expansion ratio and half life time. The graph plotted keeping Bitumen water contenton X-axis and expansion ratio and half life were kept on Y-axis. From this study and looking in tothe figure 3.4 optimum bitumen water content was decided as (2.7+3.8)/2=3.25 % of bitumen.After studying the bitumen foam behaviour at different air pressures, temperatures and bitumenwater contents it is concluded to take optimum air pressure, temperature and bitumen watercontents as 4.3 bars, 155 to 160 0C and 12 l/h (i.e. 3.3% of bitumen) respectively to produceacceptable bitumen foam and were fallowed while producing foamix. Laboratory and Field Evaluation of Recycled Cold Mixes 56
  • Figure3. 5: WLB 10- Wirtgen foamed bitumen lab kitTable3. 9: Air pressure Influence on expansion ratio and half time of Foamed bitumen 1st measurement 2nd measurement 3rd measurement average value Air Maximum Maximum Maximumpressure, foam Half foam Half foam Half Expansion Half bars height, in life, s height, in life, s height, in life, s ratio life, s cm cm cm 3 8 8 10 7 9 8 7.50 7.67 4 9 7 9.5 8 8.5 8 7.50 7.67 5 11 5.5 13 5.5 11.5 5 9.86 5.33 6 12.5 4 13 4.5 12.5 5 10.56 4.50 12 9 11 8 10 7 Half life, seconds Expansion ratio 9 6 8 5 7 4 6 3 5 2 exp ratio 4 1 half life in seconds 3 0 2.5 3 3.5 4 4.5 5 5.5 6 6.5 Air pressure, bar Figure3. 6: Air pressure Influence on expansion ratio and half time of Foamed bitumen Laboratory and Field Evaluation of Recycled Cold Mixes 57
  • Table3. 10: Bitumen temperature Influence on expansion ratio and half time of Foamed bitumen 1st measurement 2nd measurement 3rd measurement average value Bitumen Maximum Maximum Maximumtemparature,0C foam foam foam Half life, s Half life, s Half life, s Expansion ratio Half life, s height, in height, in height, in cm cm cm 150 8 8 8.5 6 10 7.5 7.36 7.17 160 10 4 11 5.5 11 6 8.89 5.17 170 11 4.25 13 4.5 11.5 4.25 9.86 4.33 180 12.5 3.5 13 3.5 12 3 10.42 3.33 12 9 11 8 10 7 Half life, seconds Expansion ratio 9 6 8 5 7 4 6 3 5 2 exp ratio 4 1 half life in seconds 3 0 145 150 155 160 165 170 175 180 185 Tem perature, 0C Figure3. 7: Bitumen temperature Influence on expansion ratio and half time of Foamed bitumenTable3. 11: Study of Bitumen water content Influence on expansion ratio and half life time ofFoamed bitumen 1st measurement 2nd measurement 3rd measurement average valueBitumen Flow- Water Maximum Maximum Maximum through, Half Half Halfcontent, foam foam foam Expansion Half l/h life, life, life, % height, in height, in height, in ratio life, s s s s cm cm cm 2.22 8 7 10 9.5 9.5 10.5 9 7.50 9.50 2.50 9 8.5 8 11.5 8 9.5 8 8.19 8.00 3.33 12 10 7 12 7 10.5 7 9.03 7.00 3.89 14 11 6 12.5 5.5 11 7.5 9.58 6.33 4.17 15 13.5 5 14 5 13.5 5 11.39 5.00 Laboratory and Field Evaluation of Recycled Cold Mixes 58
  • 12 9 11 8 Half life, seconds Expansion ratio 10 7 9 6 8 5 7 4 6 3 5 exp ratio 2 4 half life 1 3 0 2.0 2.5 3.0 3.5 4.0 4.5 Bitumen water content, % Figure3. 8: Bitumen water content Influence on expansion ratio and half life time of Foamed bitumen3.3 Emulsion TestingTable3. 12: Tests on Emulsion Emulsion Property Observed value Specified value Residue on evaporation, Minimum % 66.5% 60% Viscosity, saybolt furol viscometer At 250C, seconds 48 30-150 Storage stability after 24 hours, Maximum 1.8% 2% Charge positive positive Miscibility with water No coagulation No coagulationTests on residue: Penetration @250C, 100g, 5 seconds 85 60-120 Ductility @270C, cm, minimum 68 503.4 Mineral Aggregate ProportionsBased on pulverized RAP and stone dust gradation their proportions were fixed to meet thegradation requirement for Foamed bitumen treatment. Four different options of aggregateproportions were chosen with different quantity of filler (table 3.7). And the same aggregateproportions were fallowed for Emulsion treatment also. The details of aggregate proportions andthe gradation charts are given in Tables 3.8, 3.9, 3.10 and 3.11 and Figures 3.5, 3.6, 3.7 and 3.7respectively. Laboratory and Field Evaluation of Recycled Cold Mixes 59
  • Table3. 7: Different options of aggregate proportions RAP Stone Dust FillerOption: 1 54.00% 46.00% 0.00%Option: 2 53.46% 45.55% 0.99%Option: 3 52.94% 45.10% 1.96%Option: 4 52.40% 45.70% 2.90%Table3. 8: Option1 Material proportions sieve size, Cumulative % passing Trials percentages combined specified limits mm RAP SD RAP SD filler grading upper lower 37.5 100 100 54.00 46.00 0.00 100.00 100.00 100.00 26.5 99.24 100.00 53.59 46.00 0.00 99.59 100.00 85.37 19 95.02 100.00 51.31 46.00 0.00 97.31 100.00 73.33 13.2 74.72 100.00 40.35 46.00 0.00 86.35 86.81 62.07 9.5 52.12 100.00 28.14 46.00 0.00 74.14 76.63 53.37 6.7 39.17 100.00 21.15 46.00 0.00 67.15 67.34 45.44 4.75 29.10 93.40 15.71 42.96 0.00 58.68 59.52 38.75 2.36 16.66 72.00 9.00 33.12 0.00 42.12 46.89 27.97 1.18 7.58 50.60 4.09 23.28 0.00 27.37 37.75 20.16 0.6 5.32 43.60 2.87 20.06 0.00 22.93 31.20 14.56 0.425 3.46 35.80 1.87 16.47 0.00 18.34 28.55 12.30 0.3 2.03 26.20 1.09 12.05 0.00 13.15 26.26 10.35 0.075 0.25 9.00 0.14 4.14 0.00 4.28 20.00 5.00Table3.9: Option2 Material proportions sieve Cumulative % specified Trials percentages combined size, passing limits grading mm RAP SD RAP SD filler upper lower 37.5 100 100 53.47 45.55 0.99 100.00 100 100 26.5 99.24 100.00 53.06 45.55 0.99 99.59 100 85 19 95.02 100.00 50.80 45.55 0.99 97.34 100 73 13.2 74.72 100.00 39.95 45.55 0.99 86.48 87 62 9.5 52.12 100.00 27.86 45.55 0.99 74.40 77 53 6.7 39.17 100.00 20.94 45.55 0.99 67.48 67 45 4.75 29.10 93.40 15.56 42.54 0.99 59.09 60 39 2.36 16.66 72.00 8.91 32.79 0.99 42.69 47 28 1.18 7.58 50.60 4.05 23.05 0.99 28.09 38 20 0.6 5.32 43.60 2.84 19.86 0.99 23.69 31 15 0.425 3.46 35.80 1.85 16.31 0.99 19.15 29 12 0.3 2.03 26.20 1.08 11.93 0.99 14.01 26 10 0.075 0.25 9.00 0.14 4.10 0.99 5.22 20 5 Laboratory and Field Evaluation of Recycled Cold Mixes 60
  • Table3.10: Option3 Material proportions Cumulative % specified Trials percentagessieve size, mm passing combined grading limits RAP SD RAP SD filler upper lower 37.5 100 100 52.94 45.10 1.96 100.00 100 100 26.5 99.24 100.00 52.54 45.10 1.96 99.60 100 85 19 95.02 100.00 50.31 45.10 1.96 97.36 100 73 13.2 74.72 100.00 39.56 45.10 1.96 86.61 87 62 9.5 52.12 100.00 27.59 45.10 1.96 74.65 77 53 6.7 39.17 100.00 20.74 45.10 1.96 67.80 67 45 4.75 29.10 93.40 15.40 42.12 1.96 59.49 60 39 2.36 16.66 72.00 8.82 32.47 1.96 43.25 47 28 1.18 7.58 50.60 4.01 22.82 1.96 28.79 38 20 0.6 5.32 43.60 2.81 19.66 1.96 24.44 31 15 0.425 3.46 35.80 1.83 16.15 1.96 19.94 29 12 0.3 2.03 26.20 1.07 11.82 1.96 14.85 26 10 0.075 0.25 9.00 0.13 4.06 1.96 6.15 20 5Table3.11: Option4 Material proportions Cumulative % specified sieve size, passing Trials percentages combined limits mm RAP SD RAP SD filler grading upper lower 37.5 100 100 52.40 44.70 2.90 100.00 100 100 26.5 99.24 100.00 52.00 44.70 2.90 99.60 100 85 19 95.02 100.00 49.79 44.70 2.90 97.39 100 73 13.2 74.72 100.00 39.15 44.70 2.90 86.75 87 62 9.5 52.12 100.00 27.31 44.70 2.90 74.91 77 53 6.7 39.17 100.00 20.53 44.70 2.90 68.13 67 45 4.75 29.10 93.40 15.25 41.75 2.90 59.90 60 39 2.36 16.66 72.00 8.73 32.18 2.90 43.81 47 28 1.18 7.58 50.60 3.97 22.62 2.90 29.49 38 20 0.6 5.32 43.60 2.79 19.49 2.90 25.18 31 15 0.425 3.46 35.80 1.81 16.00 2.90 20.72 29 12 0.3 2.03 26.20 1.06 11.71 2.90 15.67 26 10 0.075 0.25 9.00 0.13 4.02 2.90 7.06 20 5 Laboratory and Field Evaluation of Recycled Cold Mixes 61
  • upper limit 0 10 lower limit combined Percent passing RAP 80 SD 40 60 20 0 0.01 0.1 1 10 100 sieve size, mm (log scale) Figure3. 5: option1 gradation curves 0 lowerlimit10 upperlimit combined achievedPercentage passing 0 8 RAP stone dust 4 20 0 0 6 0.01 0.1sieve size, mm (log scale) 10 1 100 0 Figure3. 6: option2 gradation curves Laboratory and Field Evaluation of Recycled Cold Mixes 62
  • lowerlimit 010 upperlimit combined achievedPercentage passing 0 RAP 4 20 0 0 6 8 stone dust 0.01 0.1 1 10 100 0 sieve size, mm (log scale) Figure3. 7: option3 gradation curves lowerlimit 0 10 upperlimit combined achievedPercentage passing 80 RAP stone dust 40 60 20 0.01 0.1 1 10 100 0 sieve size, mm (log scale) Figure3. 8: option4 gradation curves Laboratory and Field Evaluation of Recycled Cold Mixes 63
  • 3.5 OMC Determination for Foamed Bitumen TreatmentThe pulverized and air dried RAP is separated in to three different fractions fallowing theprocedure described in Appendix A (i.e. P-19mm & R-13.2mm, P-13.2mm & R4.75mm and P-4.75). The proportioned (Option 1) and un-treated material was used to find Optimum MoistureContent with modified Proctor compaction effort for foamed bitumen treatment. The OptimumMoisture Content found to be 8.75% with a Maximum Dry Density of 2.09 g/cc. The mixingmoisture content of proportioned material was decided based on optimum moisture content (i.e.OMC=8.75%) and air dried field sample moisture content to prepare foamix. Figure3. 9: samples of separated RAP and stone dust 2.10 2.08 Dry density, g/cc 2.06 2.04 2.02 2.00 1.98 2.0 3.5 5.0 6.5 8.0 9.5 11.0 Moisture content, % Figure3. 10: OMC determination Laboratory and Field Evaluation of Recycled Cold Mixes 64
  • 3.6 OFC Determination for Emulsion TreatmentThe Optimum Fluid Content (OFC) was determined based on maximum Indirect Tensile Strength(ITS) and maximum bulk density of Marshall Specimen prepared with 1.5% hydrated lime,proportioned material (option1), 4% binder (6.02% Emulsion) and at varied percentages of watercontent. The ITS and Bulk density of the Marshall Specimen were determined after a curingperiod of 72 hours at 40 0C temperature and the testing was conducted at ambient temperature.The graph (figure 3.11) was plotted keeping total fluid content on X-axis and Bulk density andITS on Y-axis to determine the OFC of the Emulsion treated material. From the graph OptimumFluid Content was decided (10.5+10.75)/2 = 10.625%.Note: Total fluid content includes field moisture content, emulsion and additional water. 2.085 340 2.080 320 2.075 300 Bulk density, g/cc 2.070 280 2.065 260 ITS. KPa 2.060 240 2.055 220 2.050 200 2.045 180 Bulk density 2.040 160 ITS 2.035 140 9.0 9.5 10.0 10.5 11.0 11.5 12.0 Total fluid content, % Figure3. 11: OFC determination Laboratory and Field Evaluation of Recycled Cold Mixes 65
  • 3.7 Recycled Cold Mix Preparation with Foamed BitumenThe graded material and different fillers (Cement, Hydrated lime and Fly-ash) in different percentages wasmixed using pug-mill type mixer since the quantity of mix was 10 kg. Initially dry mixing of proportionedmaterial was carried out for 10 to 15 seconds then additional water was added and then in to that mixfoamed bitumen was sprayed using WLB-10 fallowing the procedure described in Appendix A.2, aftersetting the calculated and determined parameters (table 3.12) on the laboratory plant. Figure3. 12: Mineral aggregates used in the study Figure3. 13: WLB10 laboratory plant used to produce foamed bitumen Laboratory and Field Evaluation of Recycled Cold Mixes 66
  • Figure3. 14: Pug-mill type mixer used to prepare foamixLaboratory and Field Evaluation of Recycled Cold Mixes 67
  • Table 3.12: Material calculations for foamix preparation Air dried moisture content of proportioned mix (RAP+SD), MC air dry= 0.25 % Bitumen flow rate = 125 g/s OMC=8.75 % PUG MILL mixer time factor=1.0 sample with 0 % filler (Mf=0) Percent foam bitumen (Pfb) 2 3 4 5 Bulk mass of sample, g (M) 10000 10000 10000 10000 Dry Mass of sample (Md) Md= M (1+MC air dry/100) 9975.06 9975.06 9975.06 9975.06 % Water to be added, (Pw) Pw=1+(0.5xOMC-MC airdry) 5.13 5.13 5.13 5.13 Mass of water, g (Mw) Mw=Pw x (Md+Mf)/100 511.22 511.22 511.22 511.22 Mass of bitumen, g (Mb) Mb=Pfb x( Md+Mf)/100 199.50 299.25 399.00 498.75 Time to be set on WLB 10, s (T) T=1.0 xMb/125 1.60 2.39 3.19 3.99 sample with 1 % filler (mass of filler, Mf = 100 g ) Percent foam bitumen (Pfb) 2 3 4 5 Bulk mass of sample, g (M) 10000 10000 10000 10000 Dry Mass of sample,g (Md) Md= M (1+MC air dry/100) 9975.06 9975.06 9975.06 9975.06 % Water to be added, (Pw) Pw=1+(0.5xOMC-MC airdry) 5.13 5.13 5.13 5.13 Mass of water, g (Mw) Mw=Pw x (Md+Mf)/100 516.35 516.35 516.35 516.35 Mass of bitumen, g (Mb) Mb=Pfb x( Md+Mf)/100 201.50 302.25 403.00 503.75 Time to be set on WLB 10, s (T) T=1.0 xMb/125 1.61 2.42 3.22 4.03 sample with 2 % filler (mass of filler, Mf = 200 g ) Percent foam bitumen (Pfb) 2 3 4 5 Bulk mass of sample, g (M) 10000 10000 10000 10000 Dry Mass of sample,g (Md) Md= M (1+MC air dry/100) 9975.06 9975.06 9975.06 9975.06 % Water to be added, (Pw) Pw=1+(0.5xOMC-MC airdry) 5.13 5.13 5.13 5.13 Mass of water, g (Mw) Mw=Pw x (Md+Mf)/100 521.47 521.47 521.47 521.47 Mass of bitumen, g (Mb) Mb=Pfb x( Md+Mf)/100 203.50 305.25 407.00 508.75 Time to be set on WLB 10, s (T) T=1.0 xMb/125 1.63 2.44 3.26 4.07 sample with 3 % filler (mass of filler, Mf = 300 g ) Percent foam bitumen (Pfb) 2 3 4 5 Bulk mass of sample, g (M) 10000 10000 10000 10000 Dry Mass of sample,g (Md) Md= M (1+MC air dry/100) 9975.06 9975.06 9975.06 9975.06 % Water to be added, (Pw) Pw=1+(0.5xOMC-MC airdry) 5.13 5.13 5.13 5.13 Mass of water, g (Mw) Mw=Pw x (Md+Mf)/100 526.60 526.60 526.60 526.60 Mass of bitumen, g (Mb) Mb=Pfb x( Md+Mf)/100 205.50 308.25 411.00 513.75 Time to be set on WLB 10, s (T) T=1.0 xMb/125 1.64 2.47 3.29 4.11 Laboratory and Field Evaluation of Recycled Cold Mixes 68
  • 3.8 Recycled Cold Mix Preparation with EmulsionThe graded material and different fillers (Cement, Hydrated lime and Fly-ash) in differentpercentages that were used in foamix preparation, the same combination of materials used exceptthe binder bitumen emulsion instead of foamed bitumen. Hobart mixer was used to prepare themixture since the material quantity was 1150 grams only. Three different percentages of bitumenemulsions were tried, after mixing in the mixer a delay of 30 minutes elapsed to simulate fieldcondition and to ensure starting of emulsion breaking process before starting compaction.Marshall Specimen was cast with the mixture, the number of blows applied were 75 on each side. Figure 3.15: Hobart mixer used to prepare emulsion mixture Laboratory and Field Evaluation of Recycled Cold Mixes 69
  • 3.9 Foamed bitumen and Bitumen Emulsion treated RAP Specimen testingThe Marshall specimen prepared with formulated material have been tested for Bulk Density,Resilient modulus (MR) and Indirect Tensile Strength (ITS) after a curing period of 24 hours atroom temperature in mold and 72 hours at 40 0C after taken out of mold. And testing was carriedout at room temperature only. Duplicate samples were tested for soaked Indirect Tensile Strengthafter a soaking period of 24 hours in water bath at ambient temperature. Indirect Tension Test forResilient Modulus was carried out at a repetitive load 100 N, frequency 0.1 Hertz and at atemperature of 25 0C. The test results of bulk density, indirect tensile strength and Indirect Tensiontest for Resilient Modulus are presented in tables 3.13 and 3.14 with different binders.Field cores cut from the Foamed bitumen treated recycled pavement layer were tested for BulkDensity, Resilient modulus (MR), Indirect Tensile Strength (soaked and un-soaked) and dynamiccreep resistance. Some Laboratory cast specimens were also tested for dynamic creep resistancesince the uniaxial unconfined creep test is effective in identifying the sensitivity of asphaltmixtures to permanent deformation or rutting. Dynamic creep test was conducted underunconfined conditions at a temperature of 40 0C. The Specimens were placed in the temperaturecontrol cabinet for a minimum period of two hours for conditioning the specimen to achieve testtemperature before testing. The contact stress of 3 kPa was applied for 0.1 second and rest periodof 0.9 second at a frequency of 1 Hz. The load was applied for a maximum of 3600 cycles. Thedetails specimens and dynamic creep test results are presented in table 3.15. Figure3.16: Indirect Tensile Strength Testing Schematic diagram Laboratory and Field Evaluation of Recycled Cold Mixes 70
  • Figure3.17: Specimen setup of Indirect Tension Test for Resilient Modulus Figure3.18: Specimen setup of dynamic creep testing Laboratory and Field Evaluation of Recycled Cold Mixes 71
  • Table 3.13 Foamed bitumen Specimen test results Bulk Average Resilient ITS, kPaMold Filler Filler, Foamed Mean Resilient TSR, Density, Bulk Modulus, ID type % Bitumen, % Modulus, MPa % g/cc Density, g/cc MPa Dry Soaked 0/2/1 2.107 1211 316.74 2 2.085 1318 58 0/2/2 2.063 1425 183.41 0/3/1 2.114 2090 353.89 3 2.148 1445 73 0/3/2 2.182 800 259.87 0% 0/4/1 2.134 1845 372.66 4 2.133 1687 87 0/4/2 2.132 1528 322.41 0/5/1 2.129 2544 402.01 5 2.130 2155 79 0/5/2 2.131 1765 318.311c/2/1 Cement 2.340 2519 329.83 2 2.152 2018 891c/2/2 Cement 1.964 1517 292.941c/3/1 Cement 2.188 2585 390.23 3 2.158 2417 1041c/3/2 Cement 2.127 2250 405.37 1%1c/4/1 Cement 2.126 2132 437.23 4 2.125 2247 891c/4/2 Cement 2.125 2362 387.041c/5/1 Cement 2.148 2335 450.46 5 2.111 2399 761c/5/2 Cement 2.074 2464 343.442c/2/1 Cement 2.144 2094 435.79 2 2.142 2169 702c/2/2 Cement 2.140 2244 305.232c/3/1 Cement 2.161 2188 448.34 3 2.150 2195 902c/3/2 Cement 2.139 2201 403.76 2%2c/4/1 Cement 2.152 2278 519.35 4 2.153 2282 722c/4/2 Cement 2.155 2286 376.002c/5/1 Cement 2.126 2300 359.33 5 2.101 2277 842c/5/2 Cement 2.077 2253 301.163c/2/1 Cement 2.163 1957 484.19 2 2.141 1993 903c/2/2 Cement 2.120 2028 433.833c/3/1 Cement 2.117 2494 494.21 3 2.119 2148 863c/3/2 Cement 2.121 1802 426.57 3%3c/4/1 Cement 2.114 2058 512.92 4 2.116 2173 793c/4/2 Cement 2.118 2287 402.823c/5/1 Cement 2.110 2258 500.38 5 2.102 2324 763c/5/2 Cement 2.095 2390 382.341L/2/1 Lime 2.105 1458 319.45 2 2.084 1938 771L/2/2 Lime 2.064 2417 246.991L/3/1 Lime 2.076 2410 324.26 3 2.074 2198 741L/3/2 Lime 2.072 1986 239.23 1%1L/4/1 Lime 2.073 2026 350.48 4 2.071 2112 851L/4/2 Lime 2.068 2197 299.391L/5/1 Lime 2.052 2178 271.54 5 2.028 2074 951L/5/2 Lime 2.004 1970 257.832L/2/1 Lime 2% 2.134 2162 289.15 2 2.112 1804 962L/2/2 Lime 2.091 1446 278.042L/3/1 Lime 2.078 1664 312.80 3 2.087 1995 862L/3/2 Lime 2.097 2326 267.68 Laboratory and Field Evaluation of Recycled Cold Mixes 72
  • 2L/4/1 Lime 2.083 2469 316.85 4 2.065 2009 972L/4/2 Lime 2.047 1549 306.382L/5/1 Lime 2.018 2617 294.92 5 2.022 2403 892L/5/2 Lime 2.026 2189 262.453L/2/1 Lime 2.134 2504 304.66 2 2.130 1989 813L/2/2 Lime 2.126 1474 245.293L/3/1 Lime 2.101 1902 344.37 3 2.109 1992 883L/3/2 Lime 2.118 2081 302.73 3%3L/4/1 Lime 2.091 2502 354.63 4 2.080 2374 913L/4/2 Lime 2.070 2245 321.173L/5/1 Lime 2.066 3026 374.33 5 2.063 2414 923L/5/2 Lime 2.060 1802 345.651F/2/1 Fly-ash 2.070 1073 144.56 2 2.084 1153 251F/2/2 Fly-ash 2.097 1233 36.761F/3/1 Fly-ash 2.070 1271 187.75 3 2.071 1358 261F/3/2 Fly-ash 2.073 1445 49.46 1%1F/4/1 Fly-ash 2.034 1331 192.45 4 2.057 1398 321F/4/2 Fly-ash 2.081 1464 61.061F/5/1 Fly-ash 2.032 2312 182.64 5 2.024 17671F/5/2 Fly-ash 2.015 12222F/2/1 Fly-ash 1286 2 2.126 13152F/2/2 Fly-ash 2.126 13442F/3/1 Fly-ash 2.126 1409 187.88 3 2.118 1670 332F/3/2 Fly-ash 2.109 1931 61.57 2%2F/4/1 Fly-ash 2.110 1556 208.35 4 2.101 1833 332F/4/2 Fly-ash 2.092 2110 68.532F/5/1 Fly-ash 2.080 2143 166.07 5 2.080 21432F/5/2 Fly-ash3F/2/1 Fly-ash 2.086 979 197.16 2 2.092 929 323F/2/2 Fly-ash 2.097 879 62.333F/3/1 Fly-ash 2.042 1034 203.38 3 2.097 1205 353F/3/2 Fly-ash 2.151 1375 70.58 3%3F/4/1 Fly-ash 2.090 1687 211.73 4 2.095 1318 483F/4/2 Fly-ash 2.100 948 101.973F/5/1 Fly-ash 2.070 1638 221.03 5 2.051 1651 423F/5/2 Fly-ash 2.031 1663 91.74 Field cores 1 Cement 1.5% 3.5% 2.110 3350 525.8072 2 Cement 1.5% 3.5% 2.090 2374 403.3839 2.090 2861 155 3 Cement 1.5% 3.5% 2.108 3416 342.1538 4 Cement 1.5% 3.5% 2.035 2302 258.0461 Lab Cores2c/3.5/1 Cement 1.5% 3.5% 2.118 3133 2452c/3.5/2 Cement 1.5% 3.5% 2.168 2.125 1974 2173 259 962c/3.5/3 Cement 1.5% 3.5% 2.089 1411 2522L/3.5/1 Lime 1.5% 3.5% 2.130 3149 2012L/3.5/2 Lime 1.5% 3.5% 2.135 2.109 1508 1876 218 902L/3.5/3 Lime 1.5% 3.5% 2.063 971 285 Laboratory and Field Evaluation of Recycled Cold Mixes 73
  • 2F/3.5/1 Fly-ash 1.5% 3.5% 2.075 1371 1092F/3.5/2 Fly-ash 1.5% 3.5% 2.127 2.109 1605 1405 166 682F/3.5/3 Fly-ash 1.5% 3.5% 2.124 1240 154Table 3.14 Bitumen Emulsion Specimen test results Average Bulk Average Resilient ITS, kPaSpecimen Filler Emulsion Binder Resilient TSR, Filler Density, Bulk Modulus, ID type % % Modulus, % g/cc Density, g/cc MPa MPa Dry Soaked 0/3/1 4.51 3 2.037 1089 241.72 2.028 970 54 0/3/2 4.51 3 2.017 851 130.15 0/4/1 6.02 4 2.043 718 278.91 0% 2.041 928 91 0/4/2 6.02 4 2.039 1137 252.88 0/5/1 7.52 5 2.051 1089 241.72 2.044 1019 92 0/5/2 7.52 5 2.037 949 223.13 1c/3/1 4.51 3 2.127 1184 200.81 2.123 997 109 1c/3/2 4.51 3 2.118 809 219.41 1c/4/1 6.02 4 2.087 973 219.41 1% 2.090 1011 103 1c/4/2 6.02 4 2.092 1048 226.84 1c/5/1 7.52 5 2.080 1319 185.94 2.073 1395 114 1c/5/2 7.52 5 2.065 1471 211.97 2c/3/1 4.51 3 2.117 1075 178.50 2.111 1044 121 2c/3/2 4.51 3 2.105 1012 215.69 CEMENT 2c/4/1 6.02 4 2.084 1376 167.34 2% 2.094 1197 124 2c/4/2 6.02 4 2.102 1017 208.25 2c/5/1 7.52 5 2.091 1271 167.34 2.089 1344 111 2c/5/2 7.52 5 2.086 1416 185.94 3c/3/1 4.51 3 2.107 1288 148.75 2.111 1338 108 3c/3/2 4.51 3 2.115 1387 159.91 3c/4/1 6.02 4 2.109 1238 197.09 3% 2.092 1376 109 3c/4/2 6.02 4 2.075 1513 215.69 3c/5/1 7.52 5 2.068 1748 204.53 2.073 1331 105 3c/5/2 7.52 5 2.078 914 215.69 1L/3/1 4.51 3 2.049 1448 167.34 2.050 1402 84 1L/3/2 4.51 3 2.049 1355 141.31 1L/4/1 6.02 4 2.060 1254 182.22 1% 2.059 1300 98 1L/4/2 6.02 4 2.058 1346 178.50 1L/5/1 7.52 5 2.096 1816 238.00 2.092 1645 81 1L/5/2 7.52 5 2.087 1474 193.37 2L/3/1 4.51 3 2.030 1475 185.94 LIME 2.038 1268 72 2L/3/2 4.51 3 2.045 1062 133.87 2L/4/1 6.02 4 2.054 1551 159.91 2% 2.049 1862 91 2L/4/2 6.02 4 2.042 2174 145.03 2L/5/1 7.52 5 2.062 2270 152.47 2.067 2183 88 2L/5/2 7.52 5 2.071 2095 133.87 3L/3/1 3% 4.51 3 2.045 1017 163.62 2.026 1734 93 3L/3/2 4.51 3 2.007 2451 152.47 3L/4/1 6.02 4 2.031 2.036 2270 2007 215.69 90 Laboratory and Field Evaluation of Recycled Cold Mixes 74
  • 3L/4/2 6.02 4 2.040 1743 193.37 3L/5/1 7.52 5 2.047 3012 174.78 2.060 2680 91 3L/5/2 7.52 5 2.072 2348 159.91 2c/3.5/1 2.111 2360 226.84 2.107268 2201 116 2c/3.5/2 2.103 2041 264.03 2L/3.5/1 2.105 1409 211.97 2% 5.26 3.5 2.095507 1492 107 2L/3.5/2 2.085 1574 226.84 2F/3.5/1 2.075 763.5 122.72 2.080262 858 127 2F/3.5/2 2.084 952.5 156.19Table3.15: Dynamic Creep Test results Creep Total accumulatedS.NO Mold description stiffness, axial strain at 1 hour Remarks MPa of loading, % 1.5% Cement, 3.5% Foamed No failure 1 464.7 0.015 bitumen 1.5% Lime, 3.5% Foamed bitumen 103.124 No failure 2 0.066 1.5% Fly-ash , 3.5% Foamed 32.897 No failure 3 0.207 bitumen 1.5% Cement, 5.26% Bitumen 0.585 No failure 4 11.565 Emulsion (3.5% Binder) 1.5% Lime, 5.26% Bitumen 2.492 Specimen 5 2.7 failed at Emulsion (3.5% Binder) 1252nd cycle 1.5% Fly-ash, 5.26% Bitumen 3.117 Specimen 6 2.2 failed at Emulsion (3.5% Binder) 1054th cycle Field core of 1.5% cement, 3.5% No failure 7 30.5 0.222 Foamed bitumen Laboratory and Field Evaluation of Recycled Cold Mixes 75
  • 3.10 Benkelman Beam Deflection testingBenkelman beam deflection study has been carried out on the pavement constructed withRecycled mix of Foamed bitumen after three months of construction i.e. in the month of March2006. The interval of deflection measurement points is selected as 30 meters and initial point ismarked at a distance of 10 meters from the zero Chainage of the Road (i.e. NH-17 Junction). The 0pavement temperature observed was 37 C, The PI value and moisture content of subgrade soilfound to be 14% and 17% respectively. The temperature correction factor and moisture correctionfactor applied are -0.02 and 1.1 respectively. The average characteristic rebound deflection of thepavement found to be 1.17mm. This road can serve to a 2 million standard axles without provisionof any overlay.Table3.16: Deflection data (LHS, towards Karnataka cold Storage Pvt. ltd)Chainage, km & m 00+010 00+040 00+070 00+100 00+130 00+160 00+190 00+220 00+250 00+280 00+310Distance, m 10 40 70 100 130 160 190 220 250 280 310Corrected Rebound 0.89 0.66 1.18 0.37 0.62 0.65 0.31 0.62 0.37 1.03 1.31Deflection, mmTable3.17: Deflection data (RHS, towards Karnataka cold Storage Pvt. ltd)Chainage, km & m 00+010 00+040 00+070 00+100 00+130 00+160 00+190 00+220 00+250 00+280 00+310Distance, m 10 40 70 100 130 160 190 220 250 280 310Corrected Rebound 1.2 0.99 1.01 1.16 0.33 0.62 1.06 1.32 1.23 1.14 0.57Deflection, mm 1.50 BBD study Rebound Deflection, 1.20 0.90 mm 0.60 0.30 RHS LHS 0.00 0 30 60 90 120 150 180 210 240 270 300 330 Distance, m Figure3.19: Benkelman Beam rebound deflection variation with distance Laboratory and Field Evaluation of Recycled Cold Mixes 76
  • _________________________________________CHAPTER - 44. RESULTS AND ANALYSIS4.1 Results of Foamed Bitumen Treated RAP Marshall SpecimensBulk density:The graphs are plotted to see the variation in bulk density with active filler and foamed bitumen.The bulk density of the Marshall specimens was increased and then decreased as the foamedbitumen content increases when there was no active filler. As the cement content increases therewas no significant increase in bulk density where as the binder increase causes a decrease in bulkdensity. Maximum bulk density observed from graph 4.1a, was 2.16 g/cc at 3% foamed bitumenand 1.1% cement.When lime used as filler, increased bulk density was observed at increased lime content where asincrease in foamed bitumen decreased the bulk density. Maximum bulk density observed fromgraph 4.1b, was 2.145 g/cc at 0% filler and 3% foamed bitumen and 2.13 g/cc at 3% lime and 2%foamed bitumen.Addition of fly-ash to the mix caused decrease in bulk density.Table4.1: Maximum bulk density values from the Graphs 4.1(a, b, c) Foamed bitumen, % Cement content, % Maximum bulk density, g/cc 2 1.25 2.155 3 1.1 2.160 4 2 2.155 5 0 2.130 Foamed bitumen, % Lime content, % Maximum bulk density, g/cc 2 3 2.130 3 0 2.145 4 0 2.120 5 0 2.130 Foamed bitumen, % Fly-ash content, % Maximum bulk density, g/cc 2 1.75 2.125 3 0 2.150 4 0 2.120 5 0 2.130 Laboratory and Field Evaluation of Recycled Cold Mixes 77
  • Variation of Bulk density with Cement 2.220 2.200 2.180 Bulk density, g/cc 2.160 2.140 2.120 2.100 2.080 2% Binder 2.060 3% Binder 2.040 4% Binder 2.020 5% Binder 2.000 0% 1% 2% 3% 4% Cement content, % 2.220 Variation of Bulk density with Lime 2% Binder 2.200 3% Binder 2.180 Bulk density, g/cc 2.160 4% Binder 2.140 5% Binder 2.120 2.100 2.080 2.060 2.040 2.020 2.000 0% 1% 2% 3% 4% Lime content, % Variation of Bulk density with Fly ash 2.220 2% Binder 2.200 3% Binder 2.180 4% Binder Bulk density, g/cc 2.160 5% Binder 2.140 2.120 2.100 2.080 2.060 2.040 2.020 2.000 0% 1% 2% 3% 4% Fly ash content, %Graph4. 2:( a, b, c) Variation of bulk density with foamed bitumen and filler Laboratory and Field Evaluation of Recycled Cold Mixes 78
  • Resilient modulus (MR):The values of Resilient modulus were plotted in graphs and then linear trend lines were drawn toobserve the variation in MR with foamed bitumen and active filler. It was observed from thegraphs 4.2 a, b that the increase in foamed bitumen and increase in cement increased the MR but athigher cement contents and at higher foamed bitumen contents increase in MR was not muchsignificant. The optimum cement content ranges from 1 to 2% and optimum foamed bitumencontent ranges from 3 to 4%. The maximum MR values observed from the graphs 4.2a and b was2372 MPa at 1% cement and 5% foamed bitumen and 2350 MPa at 3% cement and 3% foamedbitumen. Similar trend was observed when the active filler used was lime with a difference ofsignificant increase in MR at higher contents of lime and foamed bitumen. The maximum MRvalues observed from the graphs 4.3a and b was 2400 MPa at 3% lime and 5% foamed bitumenand 2375 MPa at 3% lime and 4% foamed bitumen. When fly-ash used as filler the variationobserved was not much but at higher foamed bitumen contents there was an increase in MR. theMaximum MR value observed from the graph 4.4 a and b was 2125 MPa at 2% fly ash and 5%foamed bitumen. Laboratory and Field Evaluation of Recycled Cold Mixes 79
  • Table 4.2: Maximum Resilient modulus (MR) values from the Graphs 4.2(a, b) Cement content, % Foamed bitumen, % Maximum Resilient modulus, MPa 0 5 2100 1 5 2372 2 5 2270 3 5 2250 Foamed bitumen, % Cement content, % Maximum Resilient modulus, MPa 2 3 2150 3 3 2350 4 3 2350 5 3 2350 Variation of MR w ith Foam ed Bitum en and Cem ent 3500 3250 3000 Resilient modulus, MPa 2750 2500 2250 2000 1750 1500 0% Filler 1250 1% Cement 1000 2% Cement 750 3% Cement 500 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Foam ed bitum en, % Variation of MR w ith Cem ent 3500 3000 Resilient modulus, MPa 2500 2000 1500 2% Foam bitumen 3% Foam bitumen 1000 4% Foam bitumen 5% Foam bitumen 500 0% 1% 2% 3% 4% Cem ent content, % Graph4.2 :( a, b) Variation of Resilient Modulus with foamed bitumen and Cement Laboratory and Field Evaluation of Recycled Cold Mixes 80
  • Table4.3: Maximum Resilient modulus (MR) values from the Graphs 4.3 (a, b) Lime content, % Foamed bitumen, % Maximum Resilient modulus, MPa 0 5 2100 1 5 2150 2 5 2300 3 5 2400 Foamed bitumen, % Lime content, % Maximum Resilient modulus, MPa 2 3 2000 3 3 2125 4 3 2375 5 3 2400 Variation of MR w ith Foam ed bitum en and Lim e 3500 3250 3000 Resilient modulus, MPa 2750 2500 2250 2000 1750 1500 0% Filler 1250 1% Lime 1000 2% Lime 750 3% Lime 500 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Foam ed bitum en, % Variation of MR with Lime 3500 3000 Resilient modulus, MPa 2500 2000 1500 2% Foamed betumen 3% Foamed bitumen 1000 4% Foamed bitumen 5% Foamed bitumen 500 0% 1% 2% 3% 4% Lim e content, % Graph4.3 :( a, b) Variation of Resilient Modulus with foamed bitumen and Lime Laboratory and Field Evaluation of Recycled Cold Mixes 81
  • Table4.4: Maximum Resilient modulus (MR) values from the Graphs 5.6(a, b) Fly-ash content, % Foamed bitumen, % Maximum Resilient modulus, MPa 0 5 2100 1 5 1700 2 5 2125 3 5 1650 Foamed bitumen, % Fly-ash content, % Maximum Resilient modulus, MPa 2 0 1350 3 0 1500 4 0 1700 5 0 2100 Variation of MR w ith Foam ed bitum en and fly-ash 3500 0% Filler 3250 3000 1% Flyash Resilient modulus, MPa 2750 2% Flyash 2500 3% Flyash 2250 2000 1750 1500 1250 1000 750 500 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Foam ed bitum en, % Variation of MR with Flyash 3500 2% Foamed bitumen 3000 3% Foamed bitumen Resilient modulus, MPa 4% Foamed bitumen 2500 5% Foamed bitumen 2000 1500 1000 500 0% 1% 2% 3% 4% Flyash content, % Graph4.4 :( a, b) Variation of Resilient Modulus with foamed bitumen and Fly-ash Laboratory and Field Evaluation of Recycled Cold Mixes 82
  • Indirect tensile strength (ITS):The ITS values were increased and then decreased with increase in foamed bitumen. The additionof cement increased the ITS values significantly. The maximum ITS observed was 510 kPa at 3%cement and 4% foamed bitumen. When the crusher stone dust was replaced with lime it wasobserved that the decrease in ITS initially and then at higher lime content slight increase. Themaximum ITS observed was 375 kPa at 3% lime and 5% foamed bitumen. Addition of fly ashcaused to decrease the ITS drastically. The specimens with cement and lime were observed to bevery less susceptible to moisture as it was observed from soaked ITS of the specimen.Table 4.5: Maximum Dry Indirect Tensile Strength (ITS) values from the Graphs 4.5 (a, b, c) Cement content, % Foamed bitumen, % Maximum Dry Indirect Tensile Strength, kPa 0 5.00 400 1 5.00 450 2 3.25 490 3 4.00 510 Lime content, % Foamed bitumen, % 1 3.25 350 2 3.50 325 3 5.00 375 Fly-ash content, % Foamed bitumen, % 1 4.00 200 2 3.75 210 3 5.00 225Table 4.6: Maximum soaked Indirect Tensile Strength (ITS) values Cement content, % Foamed bitumen, % Maximum Soaked Indirect Tensile Strength, kPa 0 4.50 325 1 3.75 400 2 3.50 400 3 2.00 430 Lime content, % Foamed bitumen, % 1 4.0 275 2 3.5 290 3 5.0 340 Fly-ash content, % Foamed bitumen, % 1 5 75 2 5 75 3 5 100 Laboratory and Field Evaluation of Recycled Cold Mixes 83
  • Variation of Dry ITS with Foamed bitumen and cement 550 500 450 400 Dry ITS, KPa 350 300 250 200 0% Filler 150 1% Cement 100 2% Cement 50 3% Cement 0 1.5 2 2.5 3 3.5 4 4.5 5 5.5 Foam ed bitum en, % Variation of Dry ITS with Foamed bitumen and lime 550 500 450 400 Dry ITS, KPa 350 300 250 200 0% Filler 150 1% Lime 100 2% Lime 50 3% Lime 0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Foam ed bitum en, % Variation of Dry ITS with Foamed bitumen and fly-ash 550 0% Filler 500 1% Flyash 450 400 2% Flyash 3% Flyash Dry ITS, KPa 350 300 250 200 150 100 50 0 1.5 2 2.5 3 3.5 4 4.5 5 5.5 Foam ed bitum en, % Graph4.5: (a, b, c) Variation of dry ITS with foamed bitumenLaboratory and Field Evaluation of Recycled Cold Mixes 84
  • 4.2 Results of Emulsified Bitumen Treated RAP Marshall SpecimensBulk density:The graphs are plotted to see the variation in bulk density with active filler and emulsifiedbitumen. The bulk density of the Marshall specimens was decreased with increase in emulsionbinder content. Addition of cement increased the bulk density but as the cement content increasesthere was no significant change in bulk density. Maximum bulk density observed was 2.12 g/cc at3% binder and 1% cement.When lime used as filler increased bulk density was observed to increase initially but as the limecontent increased it was decreased. Maximum bulk density observed from graph 4.6(a, b), was2.14 g/cc at 3% lime and 2% emulsion binder.Table4. 16: Maximum bulk density values From the Graphs 4.6 (a, b) Cement content, % Emulsion binder, % Maximum bulk density, g/cc 0 5 2.045 1 3 2.120 2 3 2.110 3 3 2.110 Lime content, % Emulsion binder, % Maximum bulk density, g/cc 1 5 2.095 2 5 2.065 3 2 2.14 Variation of Bulk Density w ith Cem ent and em ulsion Variation of Bulk Density w ith Lim e and em ulsion 2.200 2.200 2.180 3% Binder 3% Binder 2.180 2.160 4% Binder 4% Binder 2.160 2.140 5% Binder 5% Binder Bulk Density, g/cc Bulk Density, g/cc 2.140 2.120 2.120 2.100 2.100 2.080 2.080 2.060 2.060 2.040 2.040 2.020 2.020 2.000 2.000 1.980 1.980 0% 1% 2% 3% 4% 0% 1% 2% 3% 4% Cem ent content, % Lim e content, % Graph4.6 :( a ,b) Variation of bulk density with Bitumen Emulsion Laboratory and Field Evaluation of Recycled Cold Mixes 85
  • Resilient modulus (MR):The values of Resilient modulus were plotted in graphs and then linear trend lines were drawn toobserve the variation in MR with emulsion and active filler. It was observed from the graphs 4.7 a,b that MR was increased with both binder content and active fillers (lime and cement). Theincrease in MR was not much significant with cement but with lime at 5% binder, increase in MRwas significant. In comparison with cement lime showed much better MR values at same bindercontents. The maximum MR values observed from the graphs 4.7a and b was 2650 MPa at 3%lime and 5% emulsified binder and 1400 MPa at 3% cement and 3% emulsified binder.Table4. 17: Maximum Resilient Modulus values from the Graphs 4.7 (a, b) Cement content, % Emulsion binder, % Maximum Resilient Modulus, MPa 0 5 1000 1 5 1350 2 5 1400 3 3,4,5 1400 Lime content, % 0 5 1000 1 5 1600 2 5 2250 3 5 2650 Variation of MR with Cement and emulsion Variation of MR with Lime and emulsion 1600 3000 1400 2500 Resilient modulus, MPa Resilient modulus, MPa 1200 1000 2000 800 1500 600 1000 400 3% Binder 3% Binder 500 4% Binder 200 4% Binder 5% Binder 5% Binder 0 0 0% 1% 2% 3% 4% 0% 1% 2% 3% 4% Cem ent content, % Lim e content Graph4.7 :( a, b) Variation of Resilient Modulus with Bitumen Emulsion Laboratory and Field Evaluation of Recycled Cold Mixes 86
  • Indirect tensile strength (ITS):The ITS values were increased and then decreased with increase in emulsion. The addition ofcement decreased the ITS. The maximum dry and soaked ITS observed was 275 kPa at 0% cementand 4% binder and 250 kPa at 0% cement and 4% binder respectively. Addition of lime caused todecrease the ITS. The specimens with cement and lime were observed to be very less susceptibleto moisture as it was observed from soaked ITS of the specimen. It was observed that soaked ITSof cement treated material was slightly more than the dry ITS.Table 4. 18: Maximum Dry and Soaked Indirect Tensile Strength (ITS) values from the Graphs 4.8(a, b) and 4.9 (a, b). Cement content, % Emulsion binder, % Maximum Dry Indirect Tensile Strength, KPa 0 4 275 1 4 220 2 3 175 3 4.5 200 Cement content, % Emulsion binder, % Maximum Soaked Indirect Tensile Strength, KPa 0 4 250 1 4 225 2 3 220 3 4 220 Lime content, % Emulsion binder, % Maximum Dry Indirect Tensile Strength, kPa 1 5 240 2 3 180 3 4 220 Lime content, % Emulsion binder, % Maximum Soaked Indirect Tensile Strength, kPa 1 5 190 2 4 150 3 4 200 Laboratory and Field Evaluation of Recycled Cold Mixes 87
  • Variation of Dry ITS w ith em ulsion and cem ent Variation of Soaked ITS w ith em ulsion and cem ent 550 550 0% Filler 0% filler 500 500 1% Cement 1% cement 450 450 2% Cement 2% Cement 400 3% Cement 400 350 3% cement 350ITS, KPa ITS, KPa 300 300 250 250 200 150 200 100 150 50 100 0 50 2.5 3.0 3.5 4.0 4.5 5.0 5.5 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Binder content, % Binder content, % Graph4.8: (a, b) Variation of ITS with Bitumen Emulsion and Cement Variation of Dry ITS w ith em ulsion and lim e Variation of Soaked ITS w ith em ulsion and lim e 550 550 0% Filler 0% filler 500 500 1% Lime 1% Lime 450 450 400 2% Lime 400 2% Lime 350 3% Lime 350 3% LimeITS, KPa ITS, KPa 300 300 250 250 200 200 150 150 100 100 50 50 0 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Binder content, % Binder content, % Graph4.9 :( a, b) Variation of ITS with Bitumen Emulsion and lime Laboratory and Field Evaluation of Recycled Cold Mixes 88
  • 4.3 Field and Laboratory Core ComparisonComparison of Field cores and Lab cores were made with same binder i.e. foamed bitumen 3.5%and different fillers of 1.5% (Viz. Cement, Lime and Fly-ash). The MR and ITS of field coreswere higher than the laboratory cast cores but the bulk density of the field cores were less whencompared with laboratory cast cores. MR and ITS of Laboratory Cores with fly-ash were poorwhen compared with filler as lime or cement. Resilient Modulus variation in different cores 3500 3000 2861 Resilient modulus, MPa 2500 2173 1876 2000 1405 1500 1000 500 0 Field core Lab core with Cement Lab core with Lime Lab core with Flyash Dry ITS Variation in different cores 350 300 300 256 243 250 ITS, kPa 200 160 150 100 50 0 Field core Lab core with cement Lab core with Lime Lab core with Flyash Variation of bulk density in different cores 2.220 2.200 2.180 Bulk density, g/cc 2.160 2.140 2.125 2.120 2.109 2.109 2.100 2.090 2.080 2.060 2.040 2.020 2.000 Field core lab core with Cement lab core with Lime lab core with Flyash Graph4.10 :( a, b, c) Variation of Resilient Modulus, Bulk density and ITS in different cores Laboratory and Field Evaluation of Recycled Cold Mixes 89
  • 4.4 Dynamic Creep Test Results AnalysisLaboratory cores prepared with foamed bitumen and cement were very strong against dynamicaxial loading in comparison with any other cores, even field cores. Field cores have shown verypoor resistance in comparison with laboratory cores. Accumulated axial strain was nominal in caseof foamed bitumen treated cores in comparison with emulsion treated cores. The cores treated withemulsion & lime and emulsion & fly ash have failed before completion of total number of loadingcycles. Laboratory cores with emulsion and cement have shown better resistance in comparisonwith other emulsion treated cores. At 3.5%Foamed bitumen and 1.5% filler 0.25 cement Acumulated axial strain, % lime 0.2 fly-ash 0.15 field core 0.1 0.05 0 0 1000 2000 3000 4000 Num ber of cycles At 5.25% Emulsion(3.5% Binder) and 1.5% filler 3.5 cement 3 lime Accumulated axial strain, % fly-ash 2.5 2 1.5 1 0.5 0 0 1000 2000 3000 4000 Num ber of cycles Graph4.11 :( a, b, c) Variation of Accumulated axial strain with Number of cycles Laboratory and Field Evaluation of Recycled Cold Mixes 90
  • At 3.5% binder and 1.5% cement 0.6 0.5 Accumulated axial strain, % foamed botumen Emulsion 0.4 0.3 0.2 0.1 0 0 1000 2000 3000 4000 Num ber of cycles At 3.5% binder and 1.5% Lime 3 2.5 Acculmulated axial strain, % Emulsion 2 Foamed bitumen 1.5 1 0.5 0 0 1000 2000 3000 4000 Num ber of cycles At 3.5% binder and 1.5% flyash 3.5 3 Emulsion Accumulated sxial strain, % 2.5 Foamed bitumen 2 1.5 1 0.5 0 0 1000 2000 3000 4000 Num ber of cyclesGraph4.12 :( a, b) Variation of Accumulated axial strain with Number of cycles Laboratory and Field Evaluation of Recycled Cold Mixes 91
  • ________________________________________CHAPTER – 55. CONCLUSIONSThe following conclusions are drawn based on the studies performed on emulsion treated andfoamed bitumen treated RAP in laboratory and Field. In comparison with bitumen emulsion, foamed bitumen treated RAP has shown better bulk density, indirect tensile strength, resilient modulus and dynamic creep stiffness with same aggregate and gradation Loss of strength on soaking is very less with foamed bitumen and lime/cement treated material, in most of the cases the tensile strength ratio ranges from 70 to 100% and it is 155% in case of field cores Emulsion treated RAP with cement has shown higher soaked ITS than dry ITS In view of bulk density, indirect tensile strength, resilient modulus and dynamic creep stiffness, out of three fillers used in the present study cement has shown best results in combination with foamed bitumen and the optimum cement content ranges from 1 to 2% by weight aggregates. At higher cement contents improvement in properties are not much significant Lime has shown almost similar densities, ITS and MR values to compare with cement treated materials at higher lime contents Fly-ash in combination with foamed bitumen of 5% has shown a minimum MR of 1500 MPa and minimum dry ITS of 200 kPa. In combination with cement and foamed bitumen the fly-ash could be a use full material to treat the existing materials Loss of ITS on soaking in fly-ash and foamed bitumen treated RAP was considerable i.e. tensile strength ration ranges from 25 to 50% Cores cut from the foamed bitumen treated pavement have shown higher ITS and MR values in comparison with laboratory cast cores Dynamic creep stiffness of Cores from the field was very less in comparison with laboratory cast cores but they were comparable to HMA cores Benkelman beam deflection study on foamed bitumen treated pavement shows that it was structurally sound with an average characteristic rebound deflection of 1.17mm and no functional failure was observed Laboratory and Field Evaluation of Recycled Cold Mixes 92
  • ________________________________________CHAPTER – 66. APPENDICESAppendix 1: Material Sampling and blending1.1 Field samplingBulk samples are obtained during field investigations and test pit excavations. Each layer in theupper pavement (± 300 mm) must be sampled separately and at least 150 kg of material isrecovered from each layer that is likely to be included in any mix design procedure.1.2 Preparation of samples for mix design procedure1.2.1 Standard soil testsDetermine the grading (ASTM D 422) and plasticity index (ASTM D 4318) of the materialsampled from each individual layer.1.2.2 Sample blendingWhere necessary, blend the materials sampled from the different layers to obtain a combinedsample representing the material from the full recycling depth. The in-situ density of the variouscomponents must be considered when blending materials, as illustrated in the boxed examplebelow. Repeat the tests described in 1.2.1 above to determine the grading and plasticity index ofthe blended sample.1.2.3 Representative proportioningSeparate the material in the representative sample into the following four fractions:i. Retained on the 19.0 mm sieve;ii. Passing the 19.0 mm sieve, but retained the 13.2 mm sieve;iii. Passing the 13.2 mm sieve, but retained on the 4.75 mm sieve; andiv. Passing the 4.75 mm sieve. Laboratory and Field Evaluation of Recycled Cold Mixes 93
  • Reconstitute representative samples in accordance with the grading up to the portion passing the19.0 mm sieve. Substitute the portion retained on 19.0 mm sieve with material that passes the 19.0mm sieve, but is retained on the 13.2 mm sieve. The example in the table below explains thisprocedure:If there is insufficient material (i.e. passing the 19.0 mm sieve but retained on the 13.2 mm sieve)for substituting that retained on the 19 mm sieve, then lightly crush the material retained on the19.0 mm sieve to provide more of this fraction.1.2.4 Sample quantitiesThe guidelines shown in Table 7.1 should be used for the quantity of material required for therespective tests: Table 7.1 Test Sample quantity required Modified proctor, AASHTO T180 5 x 7 kg Indirect Tensile Strength (150mm Dia) 20 kg per stabiliser content Unconfined Compressive Strength (150mm Dia) 20 kg per stabiliser content Bituminous Stabilization Design (Marshall briquettes) Minimum 10 kg per stabiliser content Moisture contents Approximately 1kg1.2.5 Hygroscopic moisture contentTwo representative air-dried samples, each approximately 1 kg, are used to determine thehygroscopic (air dried) moisture content of the material. (Note: Larger sample size should be usedfor more coarsely graded materials.) Weigh the air-dried samples, accurate to the nearest 0.1 g,and then place them in an oven at a temperature of between 105 ºC and 110 ºC until they achieveconstant mass. The hygroscopic moisture content is the loss of mass expressed as a percentage ofthe dry mass of the sample. Laboratory and Field Evaluation of Recycled Cold Mixes 94
  • Appendix 2: Mix Design Procedure for Bitumen Stabilised Materials2.1 Active filler requirementsBitumen stabilisation is normally carried out in combination with a small amount of active filler(cement or hydrated lime). The following application rates (by mass) of hydrated lime or cementshould be used as a guide: Plasticity Index < 10 Plasticity Index: 10 - 16 Plasticity Index: >16 Add 1% Cement Add 1% Lime Pre-treat with 2% LimePretreatment requires that the lime and water be added at least 4 hours prior to the addition of thebitumen emulsion or foamed bitumen. The treated material must be placed in an air-tight containerto retain moisture. However, due to the hydration process, the moisture content should always bechecked and, if necessary, adjusted prior to adding the bitumen stabilising agent.Although the use of active fillers is recommended, in parts of the world, these agents are notreadily available. In such cases, the use of crusher dust (minus 6 mm crusher tailings) or similarmaterial can be used. Additional tests without active filler and/or with crusher dust are carried outduring the mix design process. The results of these tests allow a decision to be made as thewhether the addition of an active filler or crusher dust is warranted. Laboratory and Field Evaluation of Recycled Cold Mixes 95
  • 2. 2 Determination of Optimum Fluid Content (OFC) and Maximum DryDensity (MDD) for the treated materialNote: For foamed bitumen stabilisation, the OFC and MDD can be assumed to be the same as theOMC and MDD determined for representative samples of the untreated material.The OFC for bitumen emulsion treated material is the percentage by mass of bitumen emulsionplus additional moisture required to achieve the maximum dry density in the treated material. Asdescribed below, the OFC is determined by adding a constant percentage of bitumen emulsionwhilst varying the amount of water added.STEP 1Measure out the bitumen emulsion as a percentage by mass of the air-dried material for each offive prepared samples. The percentage of bitumen emulsion added is normally between 2 and 3%residual bitumen (e.g. for 3% residual bitumen, add 5% of a 60 % bitumen emulsion).STEP 2The bitumen emulsion and water is added to the material and mixed until uniform immediatelyprior to compacting the specimens.STEP 3Determine the OFC and MDD for the stabilised material in accordance with the modifiedmoisture-density relationship test procedure (AASHTO T-180). Laboratory and Field Evaluation of Recycled Cold Mixes 96
  • 2. 3 Preparation of bitumen stabilised material2. 3.1 Preparation of materials for bitumen emulsion stabilizationSTEP 1Place the required quantity of sample into a suitable mixing container (10 kg for the manufactureof 100 mm diameter briquettes, or 20 kg for the manufacture of 150 mm diameter briquettes).STEP 2Determine the dry mass of the sample using equation Msample = Mair-dry / (1 + (Wair-dry / 100)) Where: Msample = dry mass of the sample [g] Mair-dry = air-dried mass of the sample [g] Wair-dry = moisture content of air-dried sample [% by mass]STEP 3Determine the required percentage of active filler (lime or cement) using equation Mcement = (Cadd / 100) x Msample Where: Mcement = mass of lime or cement to be added [g] Cadd = percentage of lime or cement required [% by mass] Msample = dry mass of the sample [g]STEP 4Determine the required percentage (by mass) of bitumen emulsion using equation Memul = (RBreqd / PBE) x Msample Where: Memul = mass of bitumen emulsion to be added [g] RBreqd = percentage of residual bitumen required [% by mass] PBE = percentage of bitumen in emulsion [% by mass] Msample = dry mass of the sample [g]STEP 5Determine the amount of water to be added for optimum compaction purposes using equation Mwater = {((WOFC – Wair-dry) / 100) x Msample} – Memul Where: WOFC = optimum fluid content [% by mass] Wair-dry = moisture content of air-dried sample [% by mass] Mwater = mass of water to be added [g] Laboratory and Field Evaluation of Recycled Cold Mixes 97
  • Memul = mass of bitumen emulsion to be added [g] Msample = dry mass of the sample [g]STEP 6Mix the material, active filler, bitumen emulsion and water together until uniform. Immediatelymanufacture briquette specimens following the relevant procedure for either 100 mm or 150 mmdiameter briquettes.STEP 7Samples are taken during the compaction process to determine the moulding moisture content.2.3.2 Preparation of materials for foamed bitumen stabilization2.3.2.1 Determination of the foaming properties of the bitumenThe foaming properties of each bitumen type are characterized by:– Expansion Ratio. A measure of the viscosity of the foamed bitumen, calculated as the ratio ofthe maximum volume of the foam relative to the original volume of bitumen; and– Half-life. A measure of the stability of the foamed bitumen, calculated as the time taken inseconds for the foam to collapse to half of its maximum volume.The objective is to determine the temperature and percentage of water addition that is required toproduce the best foam properties (maximum expansion ratio and half-life) for a particular sourceof bitumen. This is achieved at three different bitumen temperatures as follows:STEP 1Heat the bitumen in the kettle of the Wirtgen WLB 10 laboratory unit with the pump circulatingthe bitumen through the system until the required temperature is achieved (normally starting with160 °C). Maintain the required temperature for at least 5 minutes prior to commencing withtesting.STEP 2Calibrate the discharge rate of the bitumen and set the timer on the Wirtgen WLB 10 to discharge500 g of bitumen.STEP 3Set the water flow-meter to achieve the required water injection rate (normally starting with 2% bymass of the bitumen).STEP 4 Laboratory and Field Evaluation of Recycled Cold Mixes 98
  • Discharge foamed bitumen into a preheated (± 75 °C) steel drum for a calculated spray time for500 g of bitumen. Immediately after the foam discharge stops, start a stopwatch.STEP 5Using the dipstick supplied with the Wirtgen WLB 10 (which is calibrated for a steel drum of 275mm in diameter and 500 g of bitumen) measure the maximum height the foamed bitumen achievesin the drum. This is recorded as the maximum volume.STEP 6Use the stopwatch to measure the time in seconds that the foam takes to dissipate to half of itsmaximum volume. This is recorded as the foamed bitumen’s half-life.STEP 7Repeat the above procedure three times or until similar readings are achieved.STEP 8Repeat steps 3 to 7 for a range of at least three water injection rates. Typically, values of 2%, 3%and 4% by mass of bitumen are used.STEP 9Plot a graph of the expansion ratio versus half-life at the different water injection rates on the sameset of axes (see the example in Figure 7.1). The optimum water addition is chosen as an average ofthe two water contents required to meet these minimum criteria.Repeat Step 1 to 9 for two other bitumen temperatures (normally 170 °C and 180 °C). Laboratory and Field Evaluation of Recycled Cold Mixes 99
  • Figure 7.1 Determination of optimum foaming water contentThe temperature and optimum water addition that produces the best foam is then used in the mixdesign procedure described below.Note: The minimum foaming properties that are acceptable for effective stabilisation are: Expansion ratio: 8 times Half-life: 6 secondsIf these minimum requirements cannot be met, the bitumen should be rejected as unsuitable forfoaming.2. 3.2.2 Sample preparation for foamed bitumen treatmentSTEP1Place the required quantity of sample into a suitable mixing container (10 kg for the manufactureof 100 mm diameter briquettes, or 20 kg for the manufacture of 150 mm diameter briquettes).STEP2Determine the dry mass of the sample using equation Msample = Mair-dry / (1 + (Wair-dry / 100)) Laboratory and Field Evaluation of Recycled Cold Mixes 100
  • Where: Msample = dry mass of the sample [g] Mair-dry = air-dried mass of the sample [g] Wair-dry = moisture content of air-dried sample [% by mass]STEP3Determine the required percentage of active filler (lime or cement) using equation Mcement = (Cadd / 100) x Msample Where: Mcement = mass of lime or cement to be added [g] Cadd = percentage of lime or cement required [% by mass] Msample = dry mass of the sample [g]STEP4Determine the percentage of water to be added for optimum mixing moisture content as calculatedusing equation A. The amount of water to be added to the sample is determined using equation B. Wadd = 1 + (0.5 WOMC – Wair-dry) ---------------- [Equation A] Mwater = (Wadd / 100) x (Msample + Mcement) ------- [Equation B] Where: Wadd = water to be added to sample [% by mass] WOMC = optimum moisture content [% by mass] Wair-dry = water in air-dried sample [% by mass] Mwater = mass of water to be added [g] Msample = dry mass of the sample [g] Mcement = mass of lime or cement to be added [g]STEP 5Mix the material, active filler and water in the mixing bowl until uniform.Note: Inspect the sample after mixing to ensure that the mixed material is not packed against thesides of the mixer. If this situation occurs, mix a new sample at a lower moisture content. Check tosee that the material mixes easily and remains in a “fluffy” state. If any dust is observed at the endof the mixing process, add small amounts of water and remix until a “fluffy” state is achieved withno dust.STEP 6Determine the foamed bitumen to be added using equation:Mbitumen = (Badd / 100) x (Msample + Mcement)Where: Mbitumen= mass of foamed bitumen to be added [g] Laboratory and Field Evaluation of Recycled Cold Mixes 101
  • Badd = foamed bitumen content [% by mass] Msample = dry mass of the sample [g] Mcement = mass of lime or cement to be added [g]STEP 7Determine the timer setting on the Wirtgen WLB 10 using equation:T = factor x (Mbitumen + Qbitumen)Where: T = time to be set on WLB 10 timer [s] Mbitumen= mass of foamed bitumen to be added [g] Qbitumen= bitumen flow rate for the WLB 10 [g/s] factor = compensation for bitumen losses on the mixing equipment.Experience has shown that a factor of 1.1 is applicable where a Hobart mixer is used and 1.0 whenusing a pug mill-type mixer.STEP 8Position the mechanical mixer adjacent to the foaming unit so that the foamed bitumen can bedischarged directly into the mixing bowl.STEP 9Start the mixer and allow it to mix for at least 10 seconds before discharging the required mass offoamed bitumen into the mixing bowl. Continue mixing for a further 30 seconds after the foamedbitumen has discharged into the mixer.STEP 10Determine the amount of water required to bring the sample to the optimum moisture contentusing equation.Mplus = (WOMC – Wsample) / 100 x (Msample + Mcement)Where: Mplus = mass of water to be added [g] WOMC = optimum moisture content [% by mass] Wsample = moisture content of prepared sample [% by mass] Msample = dry mass of the sample [g] Mcement = mass of lime or cement to be added [g]STEP 11Add the additional water and mix until uniform.STEP 12 Laboratory and Field Evaluation of Recycled Cold Mixes 102
  • Transfer the foamed bitumen treated material into a container and immediately seal the containerto retain moisture. To minimize moisture loss from the prepared sample, manufacture briquettespecimens as soon as possible following the relevant procedure for either 100 mm or 150 mmdiameter briquettes.Repeat the above steps for at least four different foamed bitumen contents.2.3.4 Manufacture of 100 mm diameter briquette specimens2.3.4.1 Compaction (Marshall Method)STEP 1Prepare the Marshall mould and hammer by cleaning the mould, collar, base-plate and face of thecompaction hammer. Note: the compaction equipment must not be heated but kept at ambienttemperature.STEP 2Weigh sufficient material to achieve a compacted height of 63.5 mm ± 1.5 mm (usually 1150 g isadequate). Poke the mixture with a spatula 15 times around the perimeter and 10 times on thesurface, leaving the surface slightly rounded.STEP 3Compact the mixture by applying 75 blows with the compaction hammer. Care must be taken toensure the continuous free fall of the hammer.STEP 4Remove the mould and collar from the pedestal, invert the briquette (turn over). Replace it andpress down firmly to ensure that it is secure on the base plate. Compact the other face of thebriquette with a further 75 blows.STEP 5After compaction, remove the mould from the base-plate and extrude the briquette by means of anextrusion jack.Note: With certain materials lacking cohesion, it may be necessary to leave the specimen in themould for 24 hours, allowing sufficient strength to develop before extracting.2.3.4.2 Curing procedurePlace the briquettes on a smooth flat tray and cure in a forced-draft oven for 72 hours at 40 °C. Removefrom oven after 72 hours and allow cooling to ambient temperature..2.3.5 Determination of optimum bitumen content for bitumen stabilised materials Laboratory and Field Evaluation of Recycled Cold Mixes 103
  • The 100 mm diameter briquettes are tested for indirect tensile strength under dry and soaked conditions.The results of the dry and soaked ITS tests are plotted against the respective bitumen content thatwas added. The added bitumen content that best meets the desired properties is regarded as theoptimum bitumen content.2.3.6. Compaction (modified AASHTO T-180 method)STEP 1Prepare and treat 24 kg of sample at the optimum bitumen content.STEP 2Where required, add sufficient moisture to bring sample to optimum compaction moisture contentand mix until uniform. Immediately after mixing, place material in an airtight container.STEP 3Take ±1 kg representative samples after compaction of the first and third briquette and dry to aconstant mass. Determine the moulding moisture using equationWmould = (Mmoist – Mdry) / Mdry x 100Where: Wmould = moulding moisture content [% by mass] Mmoist = mass of moist material [g] Mdry = mass of dry material [g]STEP 4Compact at least 4 briquettes using a 150 mm diameter split-mould, applying modified AASHTO(T-180) compaction effort (5 layers approximately 25 mm thick, 55 blows per layer using a 4.536kg hammer with a 457 mm drop).STEP 5Carefully trim excess material from briquettes, as specified in the AASHTO T-180 test method.STEP 6Carefully remove briquette from the spilt-mould and place on a smooth flat tray. Allow to stand atambient temperature for 24 hours or until the moisture content has reduced to at least 50 % ofOMC.Note: With certain materials lacking cohesion, it may be necessary to leave the specimen in themould for 24 hours, allowing sufficient strength to develop before extracting. Laboratory and Field Evaluation of Recycled Cold Mixes 104
  • Appendix 3: Strength Test Procedures3.1 Determination of Indirect Tensile Strength (ITS)The ITS test is used to test the briquettes under different moisture conditions including dry, soakedand equilibrium moisture content. The ITS is determined by measuring the ultimate load to failureof a briquette that is subjected to a constant deformation rate of 50.8 mm/minute on its diametricalaxis. The procedure is as follows:STEP 1Place the briquette onto the ITS jig. Position the sample such that the loading strips are paralleland centred on the vertical diametrical plane.STEP 2Place the load transfer plate on the top bearing strip and position the jig assembly centrally underthe loading ram of the compression testing device.STEP 3Apply the load to the briquette, without shock, at a rate of advance of 50.8 mm per minute untilthe maximum load is reached. Record the maximum load P (in kN), accurate to 0.1 kN.STEP 4Immediately after testing a briquette, break it up and take a sample of approximately 1000 g todetermine the moisture content (Wbreak). This moisture content is used to determine the drydensity of the briquette.STEP 5Calculate the ITS for each briquette to the nearest 1 kPa using equationITS = (2 x P) / (∏ x h x d) x 10000Where: ITS = indirect tensile strength [kPa] P = maximum applied load [kN] h = average height of the specimen [cm] d = diameter of the specimen [cm]STEP 6To determine the soaked ITS, place the briquettes under water at 25 °C ± 1 °C for 24 hours.Remove briquettes from water, surface dry and repeat steps 1 to 5.The “Tensile Strength Retained (TSR)” is the relationship between the soaked and un-soaked ITS Laboratory and Field Evaluation of Recycled Cold Mixes 105
  • for a specific batch of briquette specimens, expressed as a percentage using equationTSR = Soaked ITS / Un-soaked ITS x 100 Laboratory and Field Evaluation of Recycled Cold Mixes 106
  • 3.2 Indirect Tension Test for Resilient Modulus of Bituminous mixtures :(ASTM D 4123-82)Summery of test method • The repeated load indirect tension test for determining resilient modulus of bituminous mixtures is conducted by applying compressive loads with a haversine or other suitable wave form. The load is applied vertically in the vertical diametrical plane of a cylindrical specimen of asphalt concrete. The resulting horizontal deformation of the specimen is measured and with an assumed Poisson’s ratio, is used to calculate a resilient modulus. A resilient Poisson’s ratio can also be calculated using the measured recoverable vertical and horizontal deformations. • Interpretation of the deformation data as resulted in two resilient modulus values being used. The instantaneous resilient modulus is calculated using the recoverable deformation that occurs instantaneously during the unloading portion of one cycle. The total resilient modulus is calculated using the total recoverable deformation which includes both instantaneous recoverable and the time dependent continuing recoverable deformation during the unloading and rest-period portion of one cycle.Significance and use: • The values of resilient modulus can be used to evaluate the relative quality of materials as well as to generate input for pavement design or pavement evaluation and analysis. The test can be used to study effects of temperature, loading rate, rest periods etc. since the procedure is non-destructive, tests can be repeated on a specimen to evaluate conditioning as with temperature or moisture. This test method is not intended for use in specifications. Laboratory and Field Evaluation of Recycled Cold Mixes 107
  • _________________________________________CHAPTER - 77. REFERENCESWebsites 1. www.asphalt.csir.co.za 2. www.arra.org 3. www.infra.com 4. www.wirtgen.comReports and papers 1. Wirtgen cold recycling manual-2004 2. Wirtgen job reports 3. Dr. Bose.S, Dr. Sangita, M.P. singh & Girish Sharma “Use of cold mix recycling for rehabilitation of flexible pavements" 4. CAPSA99 - Muthen et al: Foamed Asphalt Mixes Mix Design Procedure 5. Ramanujam, J.M. & Fernando, D.P. 1997. Foam Bitumen Trial at Gladfield-Cunningham Highway. In: Proceedings of the Southern Region Symposium, Australia, 1997. 6. A Basic asphalt emulsion manual “Manual Series No.19” third edition 7. TRL Report TRL645 “Feasibility of recycling thin surfacing back in to thin surfacing systems” 8. CAPSA99 - Jenkins et al: Characterisation Of Foamed Bitumen 9. CAPSA99 - Engelbrecht: Manufacturing Foam Bitumen In A Standard Drum Mixing Asphalt Plant 10. Capsa99 - Lewis: Cold In Place Recycling: A Relevant Process For Road Rehabilitation And Upgrading 11. Acott, S.M. & Myburgh, P.A. 1983. Design and performance study of sand bases treated with foamed asphalt. In: Low-volume roads: third international conference. Washington, DC: (Transportation Research Record; 898), pp 290-296. 12. Acott, S.M.1979. Sand stabilisation using foamed bitumen. In: 3rd Conference on Asphalt Pavements for Southern Africa, 3rd, 1979, Durban, pp.155-172. Laboratory and Field Evaluation of Recycled Cold Mixes 108
  • 13. Akeroyd, F.M.L. & Hicks, B.J. 1988. Foamed Bitumen Road Recycling. Highways, Volume 56, Number 1933, pp 42, 43, 45.14. Akeroyd, F.M.M. 1989. Advances in foamed bitumen technology. In: Fifth conference on asphalt pavements for Southern Africa; CAPSA 89, held in Swaziland, 5-9 June 1989, Section 8, pp 1-415. Bissada, A.F. 1987. Structural response of foamed-asphalt-sand mixtures in hot environments. In: Asphalt materials and mixtures. Washington, DC: Transportation Research Board. (Transportation Research Record, 1115), pp 134-149.16. Bowering, R.H. & Martin, C.L. 1976. Foamed bitumen production and application of mixtures, evaluation and performance of pavements. in: Proceedings of the Association of Asphalt Paving Technologists, Vol. 45, pp. 453-477.17. Bowering, R.H. 1970. Properties and behaviour of foamed bitumen mixtures for road building. In: Proceedings of the 5th Australian Road Research Board Conference, held in Canberra, Australia, 1970, pp. 38-57.18. Bowering, R.H. & Martin, C.L. 1976. Performance of newly constructed full depth foamed bitumen pavements. In: Proceedings of the 8th Australian Road Research Board Conference, held in Perth, Australia, 1976.19. Brennen, M., Tia, M., Altschaeffl, A.G. & Wood, L.E. 1983. Laboratory investigation of the use of foamed asphalt for recycled bituminous pavements. In: Asphalt materials, mixtures, construction, moisture effects and sulfur. Washington, DC: Transportation Research Board. (Transportation Research Record; 911), pp 80-87.20. Castedo-Franco, L.H., Beaudoin, C.C., Wood, E.L. & Altschaeffl, A.G. 1984. Durability characteristics of foamed asphalt mixtures. In: Proceedings of the 29th Annual Canadian Technical Asphalt Association Conference, held in Montreal, Canada, 1984.21. Collings, D. 1997. Through foaming its possible to mix hot asphalt with cold, damp aggregate. Asphalt Contractor, June 1997 (Article based on the presentation at the 1997 ARRA annual meeting, San Antonio, TX).22. Joubert, G., Poolman, S. & Strauss, P.J. 1989. Foam bitumen stabilised sand as an alternative to gravel bases for low volume roads. In: 5th Conference on Asphalt Pavements for South Africa (CAPSA 89), Proceedings held in Swaziland, 5-9 June, 1989, Section 8, pp21-5. Laboratory and Field Evaluation of Recycled Cold Mixes 109
  • 23. Lancaster. J., McArthur, L. & Warwick, R. 1994. VICROADS experience with foamed bitumen stabilisation. In: 17th ARRB Conference, Proceedings held in Gold Coast, Queensland, 15-19 August, 1994, Volume 17, Part 3, pp193-211.24. Lee, D.Y. 1981. Treating marginal aggregates and soil with foamed asphalt. In: Proceedings of the Association of Asphalt Paving Technologists, Vol. 50, pp 211-150.25. Little, D.N., Button, J.W. & Epps, J.A. 1983. Structural properties of laboratory mixtures containing foamed asphalt and marginal aggregates. In: Asphalt materials, mixtures, construction, moisture effects, and sulfur. Washington, DC: Transportation Research Board. (Transportation Research Record; 911), pp 104-113.26. Maccarrone, S., Holleran, G., Leonard. D.J. & Hey, S. 1994. Pavement Recycling using Foamed Bitumen. In: 17th ARRB Conference, Proceedings held in Gold Coast, Queensland, 15-19 August, 1994, Volume 17, Part 3, pp 349-365.27. Maccarrone, S., Holleran, G, & Leonard, D.J. 1993. Bitumen Stabilisation - A New Approach To Recycling Pavements. In: AAPA Members Conference, 1993.28. Maccarrone, S., Holleran, G. & Ky, A. 1995. Cold Asphalt Systems as an Alternative to Hot Mix. In: 9th AAPA International Asphalt Conference.29. Roberts, F.L., Engelbrecht, J.C. & Kennedy, T.W. 1984. Evaluation of recycled mixtures using foamed asphalt. In: Asphalt mixtures and performance. Washington, DC: Transportation Research Board. (Transportation Research Record; 968), pp 78-85.30. Foamix asphalt advances by Ruckel, P.J. ... [et al]. In: Asphalt Pavement Construction: New Materials and Techniques. Philadelphia, PA: American Society for Testing and Materials (ASTM STP; 724), pp. 93-109.31. Ruckel, P.J., Acott, S.M. & Bowering, R.H. 1982. Foamed-asphalt paving mixtures: preparation of design mixes and treatment of test specimens. In: Asphalt materials, mixtures, construction, moisture effects and sulfur. Washington, DC: Transportation Research Board. (Transportation Research Record; 911), pp 88-95.32. Sakr, H.A. & Manke, P.G. 1985. Innovations in Oklahoma foamix design procedures. In: Asphalt materials, mixes, construction and quality. Washingtong, DC: Transportation Research Board. (Transportation Research Record;1034), pp 26-34.33. Tia, M. & Wood, L.E. 1983. Use of asphalt emulsion and foamed asphalt in cold-recycled asphalt paving mixtures. In: Low-volume roads: third international conference. Laboratory and Field Evaluation of Recycled Cold Mixes 110
  • Washington, DC: Transportation Research Board. (Transportation Research Record; 898), pp 315-322.34. Van Wyk, A., Yoder, E.J. & Wood, L.E. 1983. Determination of structural equivalency factors of recycled layers by using field data. In: Low-volume roads: third international conference. Washington, DC: Transportation Research Board. (Transportation Research Record; 898), pp 122-132.35. Van Wijk, A.J. 1984. Structural comparison of two cold recycled pavement layers. In: Design, evaluation, and performance of pavements. Washington, DC: Transportation Research Board. (Transportation Research Record; 954), pp 70-77.36. Van Wijk, A. & Wood, L.E. 1983. Use of foamed asphalt in recycling of an asphalt pavement. In: Asphalt materials, mixtures, construction, moisture effects and sulfur. Washington, DC: Transportation Research Board. (Transportation Research Record; 911), pp 96-103.37. Van Wijk. A. & Wood, L.E. 1982. Construction of a recycled pavement using foamed asphalt. In: Proceedings of the Twenty-seventh Annual Conference of Canadian Technical Asphalt Association, edited by P Turcotte, held in Edmonton, Alberta, Canada, 1982.38. CAPSA99 - van der Walt et al: The Use Of Foamed Bitumen In Full-Depth In-Place Recycling Of Pavement Layers Illustrating The Basic Concept Of Water Saturation In The Foam Process Laboratory and Field Evaluation of Recycled Cold Mixes 111