July 2009 Research Report: UCPRC-RR Authors: Eung-Jin Jeon, John Harvey, and Bruce Steven PREPARED FOR: PREPARED BY:

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1 July 29 Research Report: UCPRC-RR Comprehensive Performance Evaluation of In-Place Recycled Hot Mix Asphalt as Unbound Granular Material Authors: Eung-Jin Jeon, John Harvey, and Bruce Steven Partnered Pavement Research Center (PPRC) Strategic Plan Element No : Pulverization Deep In-Situ Recycling (DISR) using Recycled AC as Unbound Base: Field and Laboratory Testing. PREPARED FOR: California Department of Transportation Division of Research and Innovation Office of Materials and Infrastructure PREPARED BY: University of California Pavement Research Center Berkeley and Davis

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3 DOCUMENT RETRIEVAL PAGE Research Report: UCPRC-RR Title: Comprehensive Performance Evaluation of In-Place Recycled Hot Mix Asphalt as Unbound Granular Material Authors: Eung-Jin Jeon, John Harvey, and Bruce Steven Prepared for: Caltrans Client Reference No./Contract No.: SPE 2.4.2/ FHWA No.: Status: Stage 2 review draft Report Date: July 29 Work Submitted: July 17, 29 Version: 1 Abstract: This report presents a comprehensive field and laboratory investigation regarding the properties and expected performance of in-place full-depth recycling of flexible pavement as pulverized aggregate base (PAB). Materials sampling, field measurements and preliminary field observations of field performance were taken at four Caltrans pilot projects in District 2. Testing was performed on the PAB and virgin aggregate base materials. Extensive laboratory testing was performed including indicator tests, and triaxial resilient modulus and repeated load testing for permanent deformation. The laboratory testing evaluated the effects of materials source, gradation, density, compaction water content, saturation and modification with cement and lime. Gravel factors were calculated for use in the Caltrans R-value design method using mechanistic-empirical analysis. Incremental-recursive mechanistic-empirical simulations were performed comparing aggregate base with PAB. Overall the results indicate superior performance of PAB compared to Class 2 aggregate base. However, one of the four field projects showed premature fatigue cracking. It is not known if the fatigue cracking is primarily related to the hot-mix asphalt (HMA) surface layer or the pulverized base. Keywords: Recycling, pulverization, asphalt pavement, stiffness, rutting, pulverized aggregate base, mechanisticempirical, repeated load triaxial testing Proposals for implementation: Continue use of current gradation specification. Use provisional gravel factors recommended in this report. Increase required compaction from 95 percent to 1 percent relative density, if additional construction cost warranted by improved performance. Further investigate interactions of lime stabilization with PAB materials with different aggregate source types. Continue performance monitoring of projects included in this report. Related documents: Bejarano, M. (21). Evaluation of Recycled Asphalt Concrete Materials as Aggregate Base. Technical Memorandum prepared for the California Department of Transportation, District 2 Materials Branch. Pavement Research Center, Institute of Transportation Studies, University of California, Berkeley. UCPRC-TM-21-4 Steven, B., Jeon, E. J. and Harvey, J. (27) Initial Recommendation of a Gravel Factor for Pulverized Asphalt Concrete Used as an Unbound Base. Technical memorandum prepared for the California Department of Transportation (Caltrans) by the University of California Pavement Research Center, Berkeley and Davis. (UCPRC-TM-26-13) Steven, B., Lane, L. and Harvey, J. (28) Life-cycle Cost Analysis for Pulverized Hot Mix Asphalt Used as an Unbound Base. Technical memorandum prepared for the California Department of Transportation (Caltrans) by the University of California Pavement Research Center, Berkeley and Davis. (UCPRC-TM-28-9) Li, H., P. Fu, and J. Harvey. (29). Recommendation of Provisional Gravel Factors for Pulverized Asphalt Concrete Modified with Lime or Portland Cement for Use as Base. Technical memorandum prepared for the California Department of Transportation (Caltrans) by the University of California Pavement Research Center, Berkeley and Davis. (UCPRC-TM-29-2) Signatures: E.J. Jeon First Author J. T. Harvey Technical Review D. Spinner Editor J. T. Harvey Principal Investigator T. Joseph Holland Caltrans Contract Manager UCPRC-RR i

4 DISCLAIMER The contents of this report reflect the views of the authors who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the State of California or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. ACKNOWLEDGMENTS The University of California Pavement Research Center would like to acknowledge the support and advice provided by: Lerose Lane, District Materials Engineer for District 2, who initiated the project, and was the chief technical liason for most of its duration. The Caltrans Materials, Maintenance and Construction staff in District 2 for help with field section traffic closures, sampling and advice. Robert Hogan, of HQ Division of Pavement Management who provided technical review and ideas for incorporation of the results into Caltrans practice. This report was prepared under the technical direction of Terrie Bressette and William Farnbach for the Caltrans Pavement Standards Team (PST), under the chairmanship of Phil Stolarski, Tom Hoover, Peter Vacura, and Larry Rouen. The technical representative for the Division of Research and Innovation was T. Joseph Holland. The contract manager was Michael Samadian and later Joe Holland, assisted by Alfredo Rodriguez. The authors would like to thank all those involved for support and advice on this project. PROJECT OBJECTIVES The work presented in this technical memorandum was carried out as part of a forensic investigation project, Item in the Partnered Pavement Research Center (PPRC) Strategic Plan. The principal objective of the project is to evaluate a rehabilitation strategy that consists of in-situ recycling of existing failed hot mix asphalt and a portion of the aggregate base and placement and compaction on the road as a new granular layer, followed by a hot-mix asphalt overlay. The objective of this report is to present research results regarding the results of monitoring of four projects previously built by Caltrans, the mechanistic properties of this material, the effects of construction variability and treatment with lime or cement on those properties, and the results of simulation of the performance of this material using the mechanistic-empirical analysis program CalME. ii UCPRC-RR-28-15

5 EXECUTIVE SUMMARY Background and Objectives Pulverization is a three-step process that consists of in-place, full-depth recycling of flexible pavements, placement and compaction on the road as a new granular layer, and overlay with hot-mix asphalt (HMA). The recycling step includes reuse of the existing failed hot-mix asphalt and a portion of the aggregate base. Typical depths for pulverization projects range from 15 to 2 mm, although they can exceed 3 mm. At least 25 mm of the existing base is pulverized to ensure complete pulverization of the existing HMA layer, to cool the teeth of the recycling machine, and to add fines to the resulting material. The pulverized HMA is between 6 and 85 percent by mass of the pulverized aggregate base (PAB). The most suitable sites for use of pulverization have pavements with high extents of severe distress and that require a large number of digouts, pavements with large deflections due to a weak underlying base layer, and pavements that need significant corrections in profile or cross slope. Pulverization eliminates reflective cracking that occurs when overlays are placed on HMA layers with extensive cracking. The advantages of pulverization include the elimination of reflective cracking of existing cracked pavement layers through the new HMA surface, reduced use of virgin aggregate by lessening HMA thickness and/or extending its life, and reduced construction traffic delay. The work presented in this report was carried out as part of a forensic investigation project conducted as part of Strategic Plan Element of the Partnered Pavement Research Center (PPRC), titled Pulverization Deep In-Situ Recycling (DISR) using Recycled AC as Unbound Base: Field and Laboratory Testing. The goal of the project is to evaluate the pulverization rehabilitation strategy. Preliminary testing for the project was performed for Caltrans District 2 beginning in 21. A formal work plan was developed by the University of California Pavement Research Center (UCPRC) and District 2 in 25, and approved by the Pavement Standards Team (PST) and the Caltrans Division of Research and Innovation. The project had these principal objectives: 1. Perform a literature survey to determine the state-of-the-practice for this strategy outside of California. 2. Perform field testing and materials sampling on three to five pilot projects to be conducted in District 2. UCPRC-RR iii

6 3. Perform laboratory testing on the original and pulverized materials, on other Caltrans granular materials with currently accepted gravel factors, and on pulverized materials modified with lime and cement. 4. Perform field pavement condition surveys for several years after the completion of construction (dependent on continued funding) by the PPRC and longer term monitoring by Caltrans. 5. Carry out a mechanistic-empirical analysis to estimate the performance of pavements rehabilitated using the pulverization strategy and compare those results with mechanistically estimated performance and empirical performance data for new pavement structures and overlay strategies (to the extent possible, dependent on the availability of data). 6. Recommend gravel factor(s) for the pulverization strategy based on the results of Objectives 1 to 3 and Develop estimates of life-cycle cost based on cost data from the pilot projects and the results of the other objectives of this project, and compare with life-cycle cost of current rehabilitation strategies. This research report presents the results from completion of Objectives 1 through 5, along with a brief summary of Objective 6. Separate technical memoranda present the results of Objectives 6 and 7. The objectives of this project are completed with the delivery of this report. Work Performed Four pilot projects in northeastern California were used to evaluate the pulverized material and this rehabilitation strategy. Typical Class 2 aggregate base (AB) was also tested on some of those projects, and several other Class 2 AB materials were tested in the laboratory. Throughout this report, comparisons of the test results for the PAB and AB materials are presented, as are the expected performance of flexible pavement structures constructed with these types of materials. The characteristics and performance of the pulverized material were evaluated by comprehensive laboratory and field testing and analyses using those results. Field tests were used to track the long-term performance of the pavement structure, and included evaluation of field resilient response using dynamic cone penetrometer (DCP) and falling weight deflectometer (FWD) test results as well as visual condition surveys to monitor field permanent deformation responses and distresses. Triaxial testing including static shear tests, resilient modulus tests, and extensive repeated loading tests (RLT) was used to investigate resilient and permanent deformation characteristics. Additionally, laboratory index testing, iv UCPRC-RR-28-15

7 including sieve analyses, Atterberg limit tests, compaction tests, permeability tests, and aggregate shape tests, were performed to evaluate the basic properties of the pulverized material and construction quality in the field. Preliminary gravel factors for use with PAB were calculated based on mechanistic analysis of the effects of the stiffnesses of pulverized aggregate base when used without modification, and when modified with lime or cement, when compared with Class 2 aggregate base made with virgin aggregate. A recursiveincremental damage rutting model in the mechanistic-empirical flexible pavement analysis software CalME was used to predict permanent deformation of the pulverized base layer over the long term and to compare it with that of typical virgin aggregate base material. Conclusions The basic index test results showed that the pulverized material generally has lower density and higher permeability values than a typical virgin aggregate base material. The particle shape test results indicated that the particle shape of the pulverized material is more favorable to stiff resilient response than is typical aggregate base material. It was also found that the static shear strength of the pulverized material was comparable to that of the virgin aggregate material. The effects of gradation on the resilient and permanent deformation response were investigated using three representative gradations from two projects. The test results indicated that the resilient moduli of the pulverized material are similar at different gradations. However, permanent deformation of the PAB varied with changes in gradation for the ranges of gradation found on two field projects. Nevertheless, this variation did not appear to significantly reduce the performance of the pulverized material when compared with typical granular material. The effects of compaction moisture content on the performance of the pulverized material were evaluated and compared with that of typical base material. The effect of compaction moisture content on both the resilient modulus and permanent deformation resistance was significant. Dry-of-optimum compaction moisture content was the best condition for both the resilient modulus and permanent deformation resistance when tested in the as-compacted condition. The effect of saturation was evaluated on specimens of PAB and AB compacted at optimum moisture content. The resilient moduli of the one PAB evaluated after saturation were still greater than those of the UCPRC-RR v

8 one AB measured before saturation. The rutting resistance of that saturated PAB was compared to that of the saturated AB using multistage RLT permanent deformation tests which showed that for lower stresses and low numbers of repetitions their performance was similar, although the saturated PAB had superior performance at higher stress states and greater repetitions. Most base failures are related to high moisture content from poor drainage or cracked surface layers allowing water to enter the base. From these results, it could be concluded that the pulverized material performs better than typical aggregate base materials when the base layer is saturated. The effects of relative compaction on the resilient and permanent deformation response were evaluated based on multistage RLT permanent deformation tests. Performance differences between 92 percent and 95 percent compaction relative to CT 216 were not significant. On the other hand, the samples prepared at 1 percent relative compaction showed noticeable improvement on both the resilient modulus and permanent deformation resistance. Based on the field FWD testing and comprehensive multistage RLT permanent deformation test results, it can be concluded that the pulverized material is stiffer than typical aggregate base material. Multistage RLT permanent deformation test results showed that the pulverized material was not always superior to the virgin aggregate material in terms of permanent deformation resistance. In particular, permanent deformation resistance of the pulverized material at low stress levels was worse than that of the typical aggregate base material in California. However, PAB had better expected long-term performance at higher stress levels based on laboratory test data. Based on the condition survey results from the four pilot projects in District 2, rutting does not appear to be a problem on any of the four projects after three to eight years of service, with maximum rut depths on the order of 6 mm (1/4 in.). The oldest project, at Alturas, is just beginning to show fatigue cracking in the wheelpaths after eight years in service. On the other hand, the Poison Lake project is showing extensive fatigue cracking in the wheelpaths after only five years of service. The fatigue properties and compaction of the HMA at Poison Lake relative to that of the other projects is not known. The other two projects at Beckwourth and Cayton Creek have no fatigue cracking after six and three years of service, respectively. Extensive longitudinal cracking, which appears to be related to the construction process rather than traffic loading only, is present on two of the projects. All of these projects were 1-year designs using the Caltrans R-value design method. vi UCPRC-RR-28-15

9 Lime and cement modification were only evaluated for one source of PAB, which chemically would be expected to provide good results with lime compared to other sources of PAB because of the nature of the parent rock of the aggregate in the PAB. One percent cement and three percent lime (one or the other, not both in the same mix) added to modify the properties of the PAB showed that the resilient moduli and permanent deformation resistance of the samples that were modified by either lime or cement were greater than the unmodified materials, as expected. Higher levels of cement and lime content should generally be avoided to limit the shrinkage cracking that occurs when the material becomes stabilized (cemented), and decisions regarding modification should always consider the trade-offs between higher cost and better performance. Each PAB material must be tested with proposed modifiers to ensure that a sufficiently high ph is achieved so that the modification will remain chemically stable. Cement can improve the properties of most PAB materials, while lime will be expected to have different effects based in large part on the geologic origin of the PAB source material. The results from this limited testing were used with mechanistic-empirical analysis to produce these preliminary recommended gravel factors: For unmodified PAB: 1.15; For PAB modified with 1 percent cement: up to 1.2 and dependent on obtaining stiffnesses similar to those found in this study; and For PAB modified with 3 percent lime: up to 1.3 and dependent on obtaining stiffnesses similar to those found in this study. These provisional gravel factors are only valid when the PAB material includes at least 6 percent recycled HMA and the remaining material in the PAB is granular base that has not been contaminated with fines from the subgrade. The recursive incremental damage model proposed by Ullidtz was utilized to predict permanent deformation in the pulverized base layer. Model parameters were calibrated using the laboratory multistage RLT permanent deformation test results. Permanent deformation in the pulverized base layer was predicted using different traffic levels and climate zones. The simulations indicated that the PAB will likely have slightly more rutting than virgin Class 2 AB under low stress levels and light traffic, but PAB will have less rutting than virgin Class 2 AB under high stress levels and heavy traffic. In all of the simulations, the predicted rutting was far below the rutting failure criterion (12.5 mm [.5 in.] rut depth). Overall, the pulverized material (PAB) is generally stiffer than typical Class 2 aggregate base material when constructed, and the PAB remains stiffer than as-compacted virgin aggregate base even after the UCPRC-RR vii

10 PAB has been saturated, likely due to better particle shapes than those found in typical aggregate base material. PAB has less rutting resistance at low stress levels than typical granular base material used in California but greater rutting resistance at higher stress levels. Together, these results and simulations indicate that the PAB will provide better rutting resistance than a conventional aggregate base under heavy truck traffic and will provide longer fatigue lives for the HMA surface layer. Overall, the performance benefits of this rehabilitation strategy make it a viable option for flexible pavement rehabilitation. However, further investigation of the early cracking on the Poison Lake project is warranted to determine if the cracking is related to the pulverization strategy or due to another cause. Recommendations for Implementation Since the effect of different gradations on performance is not significant, the current specification for gradation does not appear to need modification. The effects of compaction moisture content and saturation on both resilient and permanent deformation response were found to be significant. During compaction, the moisture content of the pulverized material should range from dry-of-optimum to optimum in order to have matric suction to improve the resilient modulus and permanent deformation resistance. Compaction with wet-of-optimum moisture content is not recommended due to lower resilient modulus and greater permanent deformation. To prevent water damage over the life of the pavement, drainage design is important. Although the performance difference between the 92 percent and the 95 percent relative compaction (RC) samples was not significant, the performance difference between 1 percent RC and 95 percent RC was noticeable, with better compaction always leading to better performance. It was also found that the permanent deformation of the pulverized material is greater at low stress levels. To prevent permanent deformation due to the postcompaction at low stress levels, better compaction is needed. Therefore, the current specification for the compaction, which is a minimum of 95 percent relative compaction in the field, should be increased to increase stiffness and reduce rutting. The greater stiffness of PAB with compaction at 1 percent RC will likely increase its gravel factor and reduce the required HMA thickness placed over PAB. Life-cycle cost analysis (LCCA) is recommended to determine if the likely increase in construction costs is greater or less than cost savings from improved performance or thinner HMA layer resulting from this recommended change in compaction. viii UCPRC-RR-28-15

11 It is recommended for all projects, except those with extremely low truck traffic, that a laboratory investigation be undertaken using PAB material from the project to evaluate the potential effects on stiffness and permanent deformation resistance that use of lime or cement and better compaction (more than 95 percent relative compaction) might cause in counteracting the traffic. The results of the laboratory investigation should be combined with mechanistic-empirical analysis to determine expected improvements in performance; these expected improvements in performance should then be used to determine the cost-effectiveness of treatment and compaction levels using life-cycle cost analysis (LCCA). Recommendations for Further Research Monitoring of the field sections identified in this report should continue, with the results used to provide a field calibration to the CalME parameters for PAB, which can be used for recalculation of the gravel factor for PAB if needed. Future projects with lime or cement treatment should also be monitored to provide field measurements of stiffness and performance data that can be used to provide a better calibration of CalME parameters and gravel factors, and better guidance regarding the effectiveness of lime. Even though improvement of the resilient modulus and permanent deformation resistance from lime- or cement-modified pulverized material was observed, the details of the reaction were not understood. The microscopy of 4-times magnification was used to try to observe and understand the microscopic structure of the modified sample. However, it was impossible to observe the microscopic structure at this level of magnification. In order to understand the detailed reactions and microscopic structure of the modifier and the pulverized material mixture, a scanning electron microscopy (SEM) and X-ray diffractometer (XRD) study is recommended for future research. It is recommended that additional testing and analysis be performed to provide engineers with faster and more economical tests, analysis procedures, and guidelines to determine the most cost-effective modification and compaction levels for a given PAB material. This work should be combined with recently developed guidelines for full-depth recycling with foamed asphalt to provide a comprehensive recycling guideline. UCPRC-RR ix

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13 TABLE OF CONTENTS PROJECT OBJECTIVES...ii EXECUTIVE SUMMARY...iii LIST OF FIGURES... xiv LIST OF TABLES...xvii 1 INTRODUCTION Background Goal and Objectives Scope of This Report EXPERIMENT DESIGN AND TESTING Field Testing Test Section Information and Schedule Dynamic Cone Penetrometer (DCP) Testing Falling Weight Deflectometer (FWD) Testing Backcalculation of FWD Results Field Relative Compaction and R-value Laboratory Index Testing Sieve Analysis Atterberg Limits Testing Compaction Testing Permeability Testing Aggregate Shape Testing Laboratory Triaxial Testing Triaxial Testing System Static Triaxial Testing Repeated Load Triaxial (RLT) Testing FIELD TEST RESULTS Alturas Project Section Dynamic Cone Penetrometer Test Results Falling Weight Deflectometer Test Results Pavement Condition Survey Results Beckwourth Project Section Dynamic Cone Penetrometer Test Results Falling Weight Deflectometer Test Results UCPRC-RR xi

14 3.2.3 Pavement Condition Survey Results Poison Lake Project Section Dynamic Cone Penetrometer Test Results Falling Weight DeflectometerTest Results Pavement Condition Survey Results Cayton Creek Project Section Field Relative Density and R-Value Summary of Field Results Stiffness Results Condition Survey Results LABORATORY TEST RESULTS Index Test Results Particle Size Distribution Atterberg Limits Testing Compaction Testing Permeability Testing Aggregate Shape Test Static Triaxial Test Results Resilient Modulus Test Results Variability with Different Sources and Materials Effect of Different Gradation Effect of Compaction Moisture Content and Saturation Effect of Relative Compaction Effect of Modification Effect of Stress History Resilient Modulus Model Permanent Deformation Test Results Shakedown Concept Effect of Different Materials Sources Effect of Different Gradations Effect of Compaction Moisture Content and Saturation Effect of Relative Compaction Effect of Modification Effect of Number of Load Repetitions xii UCPRC-RR-28-15

15 4.4.8 Effects of Previous Stress History or Order of Stress Level Summary of Gravel Factor Analyses for PAB Without Modification and with Lime and Cement Modification Background Method of Analysis Empirical Pavement Designs based on Caltrans Method Inputs for Mechanistic Analysis Gravel Factors Using Stiffness Results for Single Source of Aggregate Gravel Factors Considering Other Sources of Aggregate SIMULATION USING A RECURSIVE-INCREMENTAL DAMAGE MODEL Calibration of Model Parameters CalME Simulation CONCLUSIONS AND RECOMMENDATIONS Conclusions Analysis of Short-Term Performance Evaluation of Preliminary Long-Term Field Performance Based on Field and Laboratory Testing Evaluation of Preliminary Long-Term Field Performance Based on Field Condition Surveys Effect of Lime or Cement Modification Estimation of Gravel Factors Prediction of Long-Term Performance using CalME Simulation Summary Recommendations for Implementation Recommendations for Further Research REFERENCES Appendix A: CalME Model Calibration Appendix B: CalME Simulations UCPRC-RR xiii

16 LIST OF FIGURES Figure 1.1: Aggregate availability in California (3)... 3 Figure 2.1: Pilot project location map (maps.google.com) Figure 2.2: Precondition pictures of the pilot project sections... 9 Figure 2.3: Description and location map of Poison Lake Project Figure 2.4: Description and location map of Cayton Creek Project Figure 2.5: Triaxial test system Figure 3.1: DCP test results of Alturas Project Section... 2 Figure 3.2: Backcalculated moduli of Alturas Project Section before and after rehabilitation (21) Figure 3.3: Backcalculated moduli of Alturas Project section (July 25) Figure 3.4: Backcalculated moduli of Alturas Project section (May 26) Figure 3.5: Alturas Project section pavement condition pictures (May 26) Figure 3.6: Pavement condition picture from Alturas Project (May 29) Figure 3.7: DCP test results of Beckwourth Project section (July 25) Figure 3.8: Backcalculated moduli of Beckwourth Project section (July 25) Figure 3.9: Pavement condition picture on Beckwourth Project (July 25) Figure 3.1: Pavement condition picture from Beckwourth Project (March 29) Figure 3.11: DCP Test Results Before and After Rehabilitation Figure 3.12: Backcalculated moduli of Poison Lake Project section after rehabilitation (July 25) (Note: westbound lane only) Figure 3.13: Backcalculated moduli of Poison Lake Project section (May 26) Figure 3.14: Pavement condition pictures from Poison Lake Project (June 29) Figure 3.15: Comparison of backcalculated modulus with DCP-calculated modulus Figure 4.1: Gradations of Alturas and Beckwourth PAB (dry sieve only), District 2 Class 2 AB (dry and wet sieve) and Caltrans gradation requirements Figure 4.2: Gradations of thirty different locations and three representative gradations of pulverized material from Poison Lake Project Figure 4.3: Gradations of twenty different locations and three representative gradations of the pulverized material from Cayton Creek Project...44 Figure 4.4: Compaction Test Results of PAB and AB Figure 4.5: Permeability test results of PAB and Class 2 AB...5 Figure 4.6: Mohr Circles and Failure Envelope for Poison Lake and Cayton Creek PAB Figure 4.7: Effect of different material types and sources Figure 4.8: Effect of gradation on the resilient moduli of Cayton Creek PAB xiv UCPRC-RR-28-15

17 Figure 4.9: Effect of different moisture contents for coarse gradation sample Figure 4.1: Effect of different moisture contents for fine gradation sample Figure 4.11: Effect of saturation for Cayton Creek PAB and District 2 AB Figure 4.12: Effect of relative compaction on the resilient modulus of PAB Figure 4.13: Effect of Modification on the resilient modulus of Cayton Creek PAB... 6 Figure 4.14: Comparison of measured with regression model moduli Figure 4.15: Effect of different sources and materials on permanent deformation Figure 4.16: Effect of different gradations on Poison Lake PAB Figure 4.17: Permanent deformation of Poison Lake PAB with different gradations without first block. 69 Figure 4.18: Effect of compaction moisture content on permanent deformation Figure 4.19: Comparison of permanent strain response of the pulverized material with virgin aggregate material at saturation Figure 4.2: Comparison of permanent strain response of Poison Lake PAB at different relative compaction Figure 4.21: Permanent deformation comparison with and without modification Figure 4.22: Million repetition repeated load triaxial test results for Cayton Creek pulverized material.. 77 Figure 4.23: Effect of stress order on Cayton Creek pulverized material Figure 4.24: Determination of the equivalent thickness of PAB for one pavement structure Figure A.1: Beckwourth Pulverized Material (p 125kPa) Figure A.2: Beckwourth Pulverized Material (p 15kPa) Figure A.3: Beckwourth Pulverized Material (p 2kPa) Figure A.4: Poison Lake Pulverized Material (Fine Gradation; p 125kPa) Figure A.5: Poison Lake Pulverized Material (Fine Gradation; p 15kPa) Figure A.6: Poison Lake Pulverized Material (Fine Gradation; p 2kPa) Figure A.7: Poison Lake Pulverized Material (Medium Gradation; p 12kPa) Figure A.8: Poison Lake Pulverized Material (Medium Gradation; p 15kPa) Figure A.9: Poison Lake Pulverized Material (Medium Gradation; p 2kPa) Figure A.1: Poison Lake Pulverized Material (Coarse Gradation; p 12kPa) Figure A.11: Poison Lake Pulverized Material (Coarse Gradation; p 15kPa) Figure A.12: Poison Lake Pulverized Material (Coarse Gradation; p 2kPa) Figure A.13: Cayton Creek Pulverized Material (Fine Gradation; p 14kPa) Figure A.14: Cayton Creek Pulverized Material (Fine Gradation; p 2kPa) Figure A.15: Cayton Creek Pulverized Material (Fine Gradation; p 25kPa) Figure A.16: Cayton Creek Pulverized Material (Medium Gradation; p 13kPa) UCPRC-RR xv

18 Figure A.17: Cayton Creek Pulverized Material (Medium Gradation; p 2kPa) Figure A.18: Cayton Creek Pulverized Material (Medium Gradation; p 25kPa) Figure A.19: Cayton Creek Pulverized Material (Coarse Gradation; p 15kPa) Figure A.2: Cayton Creek Pulverized Material (Coarse Gradation; p 2kPa) Figure A.21: Cayton Creek Pulverized Material (Coarse Gradation; p 25kPa) Figure B.1: Inland Valley Climate Zone with WIM-93 Traffic Figure B.2: Inland Valley Climate Zone with WIM-49 Traffic Figure B.3: High Desert Climate Zone with WIM-93 Traffic Figure B.4: High Desert Climate Zone with WIM-49 Traffic Figure B.5: Desert Climate Zone with WIM-93 Traffic Figure B.6: Desert Climate Zone with WIM-49 Traffic xvi UCPRC-RR-28-15

19 LIST OF TABLES Table 2.1: Location and Condition Information of Pilot Project Sections... 8 Table 2.2: Traffic and Structure Information of Pilot Test Sections...8 Table 2.3: Construction and Test Schedule... 8 Table 2.4: Heavy Weight Deflectometer Sensor Locations Table 2.5: Class 2 Aggregate Base Material Grading Requirements in California Table 2.6: Pulverized Material Grading Requirements Table 3.1: Distress Observations at Alturas Project in June Table 3.2: Distress Observations at Poison Lake Project in June Table 3.3: Distress Observations at Cayton Creek Project in June Table 3.4: Field Relative Compaction and R-Value Table 3.5: Summary of the Moduli Calculated from DCP Test Results Table 3.6: Summary of Backcalculated Moduli of PAB Table 4.1: Material Description and Basic Properties Table 4.2: Aggregate Shape Test Results Table 4.3: Summary of Static Shear Triaxial Test Results Table 4.4: Summary of Resilient Modulus Triaxial Test Results Table 5.1: Parameters Used for Typical Aggregate Base Material Table 5.2: Recursive-Incremental Damage Model Parameters of PAB and AB Table 5.3: Pavement Structure and Material Properties for the CalME Simulation Table 5.4: Weigh-In-Motion (WIM) Stations and Traffic Information Table 5.5: CalME Simulation Results... 9 UCPRC-RR xvii

20 xviii UCPRC-RR-28-15

21 1 INTRODUCTION 1.1 Background Much of the highway system in the United States was built between 195 and 198 with pavements designed to last 2 years before rehabilitation or reconstruction. Many of the low-volume roads in California were built more than 7 years ago. Nearly all of these roads are typical flexible pavement structures with hot-mix asphalt (HMA) surfaces built up through years of maintenance and rehabilitation, and granular bases and subbases. Currently many of the roads are deteriorating. Typical rehabilitation strategies used by the California Department of Transportation (Caltrans) are overlays, or milling and inlays. Options for overlay and inlay materials are HMA, rubberized gap-graded HMA (RHMA-G) and polymermodified HMA. Typical modes of failure are fatigue cracking in the wheelpaths, reflective cracking in the wheelpaths where cracks in the underlying HMA reflect up through the overlay or inlay, transverse cracking due to low temperatures, and cracking outside the wheelpaths due to a number of mechanisms. If cracking in the HMA layers has allowed water to penetrate to the granular base and subgrade layers below, there may be rutting in those layers. Digouts, where cracked and/or rutted HMA near the surface of the wheelpaths is milled out and inlaid, are used in many districts as a maintenance treatment. Digouts are also sometimes used as a pre-overlay preparation where there is wheelpath cracking. The edges of the digouts, whether done as part of maintenance or just before an overlay, may also reflect up through the overlay. Among the factors considered when selecting a rehabilitation strategy are existing pavement distress conditions, existing pavement structure, funding, and design life. According to the Flexible Pavement Rehabilitation Manual (1) published by Caltrans, the final choice of rehabilitation strategy is based on three factors: The need to provide a total structural section thickness that is adequate to resist the anticipated loading it will experience throughout its design life; Potential to resist reflective cracking; and Ability to improve ride quality. Each of these strategies relies on virgin aggregate materials, which is another consideration in selecting a rehabilitation strategy. For example, virgin materials are required for HMA overlays and inlays, and also (though far less often) for reconstruction projects that require placement of virgin aggregate base before overlay. However, in recent years sources of virgin materials have become scarce, which has resulted in increased construction costs due increased mining costs and hauling distances, as well as to more UCPRC-RR

22 stringent environmental protection requirements. Under this set of conditions, rehabilitation strategies predicated on reuse of existing in-situ road materials, and that also offer minimal traffic disruption and lowest life cycle costs, would be desirable especially if they had among their benefits the ability to: Reduce the use of finite virgin aggregate sources; Eliminate the need to dispose of old pavement materials from milling and reconstruction; and Reduce mining and hauling costs. The problem related to virgin aggregate sources in California was addressed by Kohler (2), who reported that the quantity of virgin aggregate in the state s mines and quarries with active permits decreased by about 2.5 billion tons in the five-year period 21 to 26, and that both the aggregate price at the plant site and transportation costs significantly increased. Figure 1.1shows a map of aggregate availability in California (3) in 26. According to this map, only one of the study areas in the state has adequate permitted aggregate resources to meet or exceed its projected 5-year demand for virgin aggregate, as compared to six areas in the 22 version of the map. In-place recycling is a set of rehabilitation methods that are alternatives to overlays and inlays. Possible in-place recycling options for flexible pavements include hot-mix asphalt recycling, hot in-place recycling, cold in-place recycling, full-depth recycling with foamed asphalt, and full-depth recycling including pulverization, the subject of this study. Over the years, recycling has become one of the most attractive pavement rehabilitation alternatives because recycling of existing pavement materials to produce new ones results in considerable savings in material, money, and energy (4). In-place recycling reduces the environmental costs of mining and the use of virgin material (primarily aggregate), particularly if a longer life can be obtained from the new HMA layer on top of the recycled material than would be the case for an HMA overlay of the same thickness subjected to reflective cracking, or if a thinner HMA overlay can be used to provide the same life. Pulverization includes the reuse of existing HMA and/or part of the underlying granular base or subbase layer to create a new layer. With all of these recycling technologies, a new HMA layer is placed on top of the recycled base layer. The thickness of the new HMA overlay is based on the properties of the pavement structure after in-place recycling. 2 UCPRC-RR-28-15

23 Figure 1.1: Aggregate availability in California (3). Pulverization is a three-step process that consists of in-place, full-depth recycling of flexible pavements, placement and compaction on the road as a new granular layer, and overlay with hot-mix asphalt (HMA). The recycling step includes reuse of the existing failed hot-mix asphalt and a portion of the aggregate base. Typical depths for pulverization projects range from 15 to 2 mm (.5 to.67 ft), although they can exceed 3 mm (1. ft). At least 25 mm (.8 ft) of the existing base is pulverized to ensure complete UCPRC-RR

24 pulverization of the existing HMA layer, to cool the teeth of the recycling machine, and to add fines to the resulting material. The pulverized HMA is between 6 and 85 percent by mass of the pulverized aggregate base (PAB). The most suitable projects for use of pulverization have pavements with serious distresses and that require a large number of digouts, pavements with large deflections due to weak underlying base layers, and pavements needing significant corrections in profile or cross slope. Pavements with bad drainage may not be suitable because the pulverization strategy cannot fix a drainage problem. The strategy is particularly suitable for a number of California highways in rural areas, many of which were built up to 8 years ago and have thick layers of cracked HMA and many patches. The pulverization strategy is most suitable to rural flexible pavement highways with low to moderate volume traffic because traffic should temporarily run on the PAB during construction and high traffic volumes prior to HMA paving can cause problems on the surface of the PAB such as rutting, aggregate loss and decompaction. The Caltrans draft guidelines for flexible pavement rehabilitation using pulverization (4) specifically recommends that pulverization is best used for pavements with the following conditions:: Locations requiring digouts of 2 percent or more by paving area. Structurally inadequate pavement sections, which would otherwise require a thick overlay, as indicated by: o Advanced pavement distress such as severe cracking (wider than ¼ inch (6 mm), continuous deep reflective cracking, or extensive cracking between cracked wheelpaths often referred to as Alligator C cracking or plastic deformation (shoving or rutting greater than ¾ in. [19 mm]). o Significant cracking and a deflection study with 8th percentile deflections greater than 15 mils (.38 mm). Rough surfaces that require smoothing of bumps and dips to improve ride quality. Projects that need longitudinal or transverse corrections to grade, cross-slope, or super elevation. Projects that have base deterioration due to fatigue, moisture intrusion, pumping, or other causes. 1.2 Goal and Objectives The work presented in this report was carried out as part of a forensic investigation project which is Partnered Pavement Research Center (PPRC) Strategic Plan Element (SPE) 2.4.2, titled Pulverization Deep In-Situ Recycling (DISR) using Recycled AC as Unbound Base: Field and Laboratory Testing. The goal of the project is to evaluate the pulverization rehabilitation strategy. 4 UCPRC-RR-28-15

25 Preliminary testing for the project was performed for Caltrans District 2 beginning in 21. A formal work plan was developed by the University of California Pavement Research Center (UCPRC) and District 2 in 25, and approved by the Pavement Standards Team (PST) and the Caltrans Division of Research and Innovation (DRI) (6). Work plan objectives undertaken for this project by the UCPRC include: 1. Perform a literature survey to determine the state-of-the-practice for this strategy outside of California. 2. Perform field testing and materials sampling on three to five pilot projects to be conducted in District Perform laboratory testing on the original and pulverized materials, on other Caltrans granular materials with currently accepted gravel factors, and on pulverized materials modified with lime and cement. 4. Perform field pavement condition surveys for several years after the completion of construction (dependent on continued funding) by the PPRC and longer term monitoring by Caltrans. 5. Carry out a mechanistic-empirical analysis to estimate the performance of pavements rehabilitated using the pulverization strategy and compare those results with mechanistically estimated performance and empirical performance data for new pavement structures and overlay strategies (to the extent possible, dependent on the availability of data). 6. Recommend gravel factor(s) for the pulverization strategy based on the results of Objectives 1 to 3 and Develop estimates of life-cycle cost based on cost data from the pilot projects and the results of the other objectives of this project, and compare with life-cycle cost of current rehabilitation strategies. This research report presents the results from completion of Objectives 1 through 5, along with a brief summary of Objective 6. Separate technical memoranda present the results of Objectives 6 and 7. The results of Objective 6 are presented in two technical memoranda (7, 8), with updated results for lime- and cement-treated materials included in this report. A separate technical memorandum presents the results of Objective 7 (9). The objectives of this project are completed with the delivery of this report. UCPRC-RR

26 1.3 Scope of This Report The scope of this report is as follows: Chapter 2 presents field and laboratory test procedures for the pulverized material and a description of the pilot project sections. Chapter 3 presents the field test results for the pilot project sections. Chapter 4 presents the laboratory resilient modulus and repeated load triaxial test results of the pulverized material and compares them with results from several California aggregate base materials. Chapter 4 also summarizes the gravel factor recommendations based on a simple mechanistic-empirical analysis using the Asphalt Institute models and using the results of the field and laboratory testing documented in this report. The analyses on which those recommendations are based are presented in detail in two separate technical memoranda. Chapter 5 presents prediction of the permanent deformation response of the pulverized material based on mechanistic-empirical recursive incremental damage analyses performed using incremental-recursive mechanistic-empirical analysis models included in the software package developed for Caltrans by the PPRC called CalME. Conclusions and recommendations are presented in Chapter 6. Appendix A present results of calibration of the CalME permanent deformation model for PAB using the repeated load triaxial data. Appendix B shows simulation of CalME using the calibrated model. 6 UCPRC-RR-28-15

27 2 EXPERIMENT DESIGN AND TESTING 2.1 Field Testing Field testing was conducted on several Caltrans pulverization pilot projects to monitor field performance; testing included coring and Dynamic Cone Penetrometer (DCP) and Falling Weight Deflectometer (FWD) tests, and a visual pavement condition survey. Locations of the pilot projects are illustrated in Figure 2.1. Figure 2.1: Pilot project location map (maps.google.com). Field measurements of relative compaction by nuclear gauge and R-value testing were conducted by Caltrans District 2 engineers Test Section Information and Schedule Table 2.1 summarizes the locations and climate information of the pilot projects. Climate information was obtained using data from the Western Region Climate Center (1). As presented, elevations of pilot project sections are more than 1, m, a relatively high altitude. UCPRC-RR

28 Table 2.1: Location and Condition Information of Pilot Project Sections Alturas Beckwourth Poison Lake Cayton Creek Highway US 395 State Route 7 State Route 44 State Route 89 Postmile (PM) 11 to to 86 to to 43.3 County Modoc Plumas Lassen Shasta Precipitation a (mm) , Snowfall a (mm) 5 1,54 4, Elevation (m) 1,3 1,5 1,7 1, a Average annual record. Information about traffic and pavement structure for the pilot project sections was obtained from the Caltrans database (11) and the District 2 office, and is summarized in Table 2.2. The values for annual average daily truck traffic (AADTT) in the table come from dividing the total truck traffic volume by 365 days. Thicknesses of the HMA were obtained from coring, and thicknesses of the pulverized base layer were evaluated from dynamic cone penetrometer test results. Table 2.2: Traffic and Structure Information of Pilot Test Sections Alturas Beckwourth Poison Lake Cayton Creek Lanes in each direction AADTT a year Design TI b (2) 9. (21) 9.5 (21) ESAL 2-Way c 124, 43, 56, 127, Thickness of new HMA d 15 mm 1 mm 12 mm - Thickness of PAB d 31 mm 235 mm 32 mm - a AADTT = Average Annual Daily Truck Traffic from 27 data b TI = Traffic Index. Evaluated by Caltrans District 2 (Estimated year) c ESAL = Equivalent Single Axle Load (two-way travel) from 27 data (referred to as Equivalent Axle Load [EAL] in that data) d Average value Table 2.3 summarizes construction, pavement condition before construction and field test schedules for the projects. No precondition survey was conducted on the Beckwourth project section. The evaluation of the Cayton Creek project since construction has consisted only of condition surveys. Table 2.3: Construction and Test Schedule Year Alturas Beckwourth Poison Lake Cayton Creek Construction Summer 21 Summer 23 Summer 24 Fall 26 Precondition survey? Yes No Yes Yes Severe alligator Severe alligator & Severe alligator Distresses before cracking & block cracking, & & block construction occasional longitudinal cracking, & potholing cracking raveling DCP testing Jun. & Sep. 21 a Jul. 25 Jun. 24 b & Jul. May 26 b Condition survey & FWD testing Jun. & Sep. 21 a, Jul. 25, May 26, Jun. 29 c a Conducted both before and after construction b Conducted only before construction c Condition survey only Jul. 25, Mar Jun. 24 b, Jul. 25, c Jun. 29 May 26, Jun. 29 c 8 UCPRC-RR-28-15

29 Figure 2.2 includes precondition pictures of the pilot project sections. The UCPRC database includes additional photos. (a) Alturas (b) Cayton Creek (c) Poison Lake Figure 2.2: Precondition pictures of the pilot project sections. UCPRC-RR

30 US Route 395, Modoc County (Alturas) This project is located on US 395 near Alturas, from 2.7 km (1.7 mi.) north of Juniper Creek to the Alturas overhead. Between Postmile 1 and Postmile 11 is a control section which basically has the same structure as the rest of the pilot project except that typical aggregate base was used in its construction instead of pulverized material so the two could be compared State Route 7, Plumas County (Beckwourth) This project is located on SR 7 near Beckwourth from.4 km (.25 mi.) west of Big Grizzly Creek Bridge to 2.5 km (1.6 mi.) east of Maddalena Road. Since a precondition survey was not conducted prior to rehabilitation, there was no information on the existing road State Route 44, Lassen County (Poison Lake) This project is located on SR 44 about 14 km (8.7 mi.) east of the city of Old Station in Shasta County. Prior to rehabilitation, the road showed extensive and severe alligator and block cracking. In particular, the wheelpaths were severely cracked. The description and location map of this project are illustrated in Figure 2.3. Figure 2.3: Description and location map of Poison Lake Project. 1 UCPRC-RR-28-15

31 State Route 89, Shasta County (Cayton Creek) This project is located on SR 89 in Shasta and Siskiyou Counties, from Lake Britton Bridge in Shasta County to.2 km (.1 mi.) north of the Shasta/Siskiyou county boundary. SR 89 is a California State Highway that runs in the North South direction and is the major thoroughfare for many mountain communities. The project is located about 2 km (12.5 mi.) north of Burney. The description and location map of this project is illustrated in Figure 2.4. Figure 2.4: Description and location map of Cayton Creek Project Dynamic Cone Penetrometer (DCP) Testing After the HMA cores were removed from the core holes, dynamic cone penetrometer (DCP) testing was conducted for field measurements of thickness. Several researchers (12, 13, 14) have developed the correlation between stiffness and DCP penetration rate (DN value, mm/blow). In this study, three proposed equations for unbound material were used to estimate modulus from the DCP test results. The equations are as follows: UCPRC-RR

32 where, E eff ( MPa) ( log( DN )) = 1 by CSIR (12) (1) ( 269 / ). 64 E ( MPa) = 17.6 DN by Chai and Roslie (13) (2). 39 ( ) E back ( MPa) = 338 DN by Jianzhou et al. (14) (3) E eff is the effective elastic modulus and E back is the FWD backcalculated modulus. The moduli calculated from these equations were compared with the backcalculated moduli Falling Weight Deflectometer (FWD) Testing The FWD used on the project was a Dynatest Model 882, which is often referred to as a Heavy Weight Deflectometer (HWD). This test system was used to generate the required nondestructive load-deflection data. In this study, the test loads range from 27 to 67 kn. Sensor locations used are summarized in Table 2.4. Table 2.4: Heavy Weight Deflectometer Sensor Locations Distance from Center of Sensor Number Load Plate(mm) ,535 8 a 1,985 a The eighth sensor was not used in the analysis. At every drop point, three load levels were each applied once. The FWD-generated load-deflection data was used to estimate the pavement layer moduli according to available mechanistic tools for pavement analysis. Pavement surface temperature was automatically measured by the FWD system during testing. FWD tests were generally performed in the morning and afternoon in order to evaluate the stiffness of the HMA and the pulverized material at different temperatures. Because the pulverized material includes HMA particles, temperature susceptibility of the pulverized material was investigated. FWD testing was not conducted on the Cayton Creek project section due to limitations in funding and scheduling Backcalculation of FWD Results The backcalculation analyses were conducted using the CalBack software program (15), which is currently being developed for Caltrans by the UCPRC. In this study, the Odemark-Boussinesq approach was used for the response model with a nonlinear subgrade model. 12 UCPRC-RR-28-15

33 E = C σ 1 p a n where, E denotes the subgrade modulus, σ 1 is the major principal stress, p a is atmospheric pressure (1 kpa), and C and n are constants (n being negative). A constrained Extended Kalman Filter (EKF) proposed by Choi et al. (16) was used to search for the solution. (4) Field Relative Compaction and R-value For quality control during construction, Caltrans District 2 engineers conducted field measurements of relative compaction with nuclear gauges (CTM-231), and R-value tests with the stabilometer (CTM-31). CTM-213 was conducted to determine the in-place wet density and moisture of soils and aggregates by the use of a nuclear gauge, and to determine relative compaction. 2.2 Laboratory Index Testing Index testing was carried out to understand basic properties of the material. Index tests included sieve analysis, Atterberg limits, compaction testing, permeability testing, and aggregate shape testing Sieve Analysis The particle size distribution of the pulverized material obtained in the field was determined by ASTM- C136 (dry sieving) only, or by ASTM-C136 and ASTM-C117 (wet sieving) together. Caltrans gradation requirements for Class 2 aggregate base are shown in Table 2.5 (17); gradation requirements for PAB are shown in Table 2.6. These Caltrans grading requirements are based on gradation determination using CTM 22, which requires dry and wet sieving together. CTM 22 should result in gradations similar to ASTM-C 136 and ASTM-C117 together. Table 2.5: Class 2 Aggregate Base Material Grading Requirements in California Sieve Sizes Percentage Passing 1 ½ (37.5-mm) Maximum ¾ (19-mm) Maximum Operating Range Contract Compliance Operating Range Contract Compliance 2 (5-mm) 1 1 1½ (37.5-mm) (25-mm) 1 1 ¾ (19-mm) No. 4 (4.75-mm) No. 3 (6-μm) No. 2 (75-μm) UCPRC-RR

34 Table 2.6: Pulverized Material Grading Requirements Sieve Size Percent Passing 2 (5-mm) 1 1½ (37.5-mm) 9-1 No. 2 (75-μm) Atterberg Limits Testing Atterberg limits were obtained using the ASTM test protocol D Compaction Testing Compaction tests were conducted using standard (ASTM-D 698), modified (ASTM-D1577) and Caltrans (CTM-216) methods to find the maximum dry density and optimum moisture content with different compaction energies. The test results were used to prepare the triaxial test samples with respect to different relative compactions. Current Caltrans specifications require a minimum 95 percent relative density, in accordance with the Caltrans method (CTM-216) Permeability Testing Permeability tests were performed with a constant head test (ASTM D2434) at two different compaction levels. All samples for the testing were prepared according to ASTM D5856, which covers the preparation and permeability testing of granular material. ASTM compaction and permeability tests were conducted at the same time, since the same mm diameter mold was used for both tests. After each compaction test was conducted, the sample was saturated and permeability was measured by a constant head test Aggregate Shape Testing Details about the shapes of the pulverized material and aggregate base material in California were investigated using aggregate shape tests. These tests were based on a classification methodology developed by Al-Rousan et al. (18), which classifies aggregates by shape using a distribution of their shape characteristics, and an aggregate imaging system (AIMS) developed by Masad (19), in which these aggregate characteristics were measured and analyzed. Tests were performed at Texas A&M University using AIMS and the test results were analyzed according to the methodology proposed by Al-Rousan et al. (18), which was based in part on previous research by Barrett (2) and Masad et al. (21). Details of the method of these characterization tests and analysis are also summarized in Jeon (22). 14 UCPRC-RR-28-15

35 2.3 Laboratory Triaxial Testing Triaxial Testing System A servo-hydraulic triaxial test machine at the University of California Pavement Research Center (UCPRC) Richmond Field Station was used for all the triaxial testing (23). The samples had a diameter of mm and a height of 3 mm. They were compacted using a vibratory hammer in five equal layers, and prepared with different combinations of material source, gradation, relative compaction, and moisture content. Two Linear Variable Differential Transducers (LVDTs) were mounted inside the sample and two other LVDTs were mounted on top of the sample to measure axial displacement. Axial load was measured by two internal and external load cells. A radial extensometer was used to measure radial displacement. The triaxial test system and the sample instrumentation are illustrated in Figure 2.5. Load Cell LVDT Radial Extensometer Figure 2.5: Triaxial test system Static Triaxial Testing Static triaxial testing was conducted at different confining pressures to find the shear strength of the material. The samples were tested under drained conditions using displacement control at a rate of.5 mm/sec (1% axial strain per minute). Three or four confining pressures (, 35, 7, and 15 kpa) were used to cover the range of confinement encountered under field conditions. Large pore pressures are unlikely to be generated during shearing of dense, unsaturated material, but the slow rate was chosen to ensure that any excess pore pressures had sufficient time to dissipate (23). UCPRC-RR

36 2.3.3 Repeated Load Triaxial (RLT) Testing Two of the most important features of base layer material are stiffness and permanent deformation resistance. The material should be stiff enough to have traffic-induced load-carrying ability and sufficient rutting resistance to limit rut development in the pavement structure due to the permanent deformation of the unbound layer. It is important to understand both the resilient modulus characteristics and the permanent deformation characteristics of the base layer material. Therefore, a series of multistage repeated load triaxial (RLT) permanent deformation tests were carried out. Multistage RLT permanent deformation tests proposed by Arnold et al. (24) were conducted to cover a wide range of stress states while minimizing the number of test specimens. This multistage RLT test method allowed the full ranges of stresses to be tested while only using three samples. For the same sample, the mean normal stress (p) was kept constant, and the deviatoric stress (q) was varied for each subsequent test of 5,6 load repetitions to find the shakedown limits. It was assumed that RLT permanent strain tests conducted at stress levels close to the static failure envelope line plotted in p - q stress space would result in the highest deformations. Stress blocks were chosen to cover the full range of stress conditions that occur within a pavement. RLT tests were conducted using stress blocks based on shakedown limits determined from the method proposed by Werkmeister et al. (25). After each block of 5,6 repetitions was finished, a resilient modulus test was conducted following the Strategic Highway Research Program (SHRP) P-46 test protocol. The P-46 test procedure consists of loading with 15 different stress states, with each stress state applied for 1 repetitions. After the P-46 test was finished, RLT permanent deformation tests for the next stress block of 5,6 repetitions were completed. This process was repeated until the specimen failed. In some of these tests, resilient moduli during permanent deformation testing were only measured during the first and the last 3 repetitions in each loading block, due to the limitation of file size. Test variables considered in this study were three representative gradations (fine, medium, and coarse), relative compaction, and compaction moisture content. In addition, in order to investigate the effect of saturation on the pulverized material, the sample was prepared wet of optimum moisture content and saturated using back pressure. Pressure differences to determine the degree of saturation were measured using a differential pressure transducer. Once the degree of saturation reached the target values, multistage RLT testing was conducted. 16 UCPRC-RR-28-15

37 Tests were also conducted on samples that had been modified with either lime or cement, cured for seven days, and then tested with the multistage RLT test method in order to quantify any improvements resulting from the addition of a modifying agent. Before triaxial testing, the optimum ratio of lime was determined from the initial consumption of stabilizer test proposed by Gautrans (26). The objective of this test is to control the ph of chemically-modified materials in order to allow the formation of cementitious materials and to ensure the durability of the reaction products (26). Initial consumption of lime is determined from these test results. When sufficient lime is mixed with the soil to bring its ph to 12.4, the saturation ph of lime, a series of reactions including ion exchange, flocculation, and cementation occur resulting in gains in strength and stability. The initial consumption of lime (ICL) is defined as the minimum quantity of lime that, when added to a suspension of soil in water at normal temperature will raise its ph value to Tests were conducted by measuring ph on the samples with different percentages of lime, and based on the initial consumption test, three percent of lime appears adequate for the reactions occurrence. UCPRC-RR

38 18 UCPRC-RR-28-15

39 3 FIELD TEST RESULTS 3.1 Alturas Project Section Dynamic Cone Penetrometer Test Results Dynamic Cone Penetrometer (DCP) tests were conducted before and after construction to estimate the thickness of the base layer, as illustrated in Figure 3.1. In the figure, the interface between the base and subgrade layers was estimated based on the average penetration blow counts. The average penetration blow counts after construction are greater than those before construction. Since more penetration blow counts imply a material that is more resistant to shear stresses, it can be postulated that improvement was observed. Based on the DCP test results, the moduli were estimated using the equations presented in Chapter 2 and the results are presented in Section Falling Weight Deflectometer Test Results As previously mentioned, between Postmile (PM) 1 and Postmile (PM) 11 lies a control section that has the same structure as the pulverization section except that the control section has a typical aggregate base. FWD tests were conducted in both the northbound (NB) and southbound (SB) lanes. Figure 3.2 shows the backcalculated moduli between PM-1 and PM-13 before and after rehabilitation in 21. In Figure 3.2, E_HMA is the modulus of HMA, E_AB is the modulus of the aggregate base, E_PAB is the modulus of the pulverized aggregate base, E_SG is the modulus of the subgrade, and NB and SB denote northbound and southbound lanes, respectively. As shown, the moduli of the base layer increased significantly after pulverization. It was also demonstrated that the moduli of the HMA layer changed noticeably with surface temperature change because asphalt is a viscoelastic material. However, the backcalculated moduli of the base and the subgrade (SG) layers did not change with changing surface temperature. Additional FWD tests were conducted in July 25 at the same location, four years after construction. The tests were carried out in the morning and afternoon to investigate the effect of surface temperature on the backcalculated moduli. The backcalculated moduli in the northbound and southbound lanes are illustrated in Figure 3.3. Compared with the backcalculated moduli in 21, the moduli of the pulverized base layer section showed improvement. On the other hand, the moduli of the aggregate base in the control section were similar to the 21 data. Another finding was that the backcalculated moduli of the pulverized base layer section were greater than those of the aggregate base section. Surface temperature differences between the morning and afternoon were significant. However, stiffnesses in the morning and afternoon were almost the same. This implies that the PAB stiffness is not temperature sensitive, even though the pulverized HMA is between 6 and 85 percent of the mass of the PAB. One factor contributing to the lack of temperature sensitivity could be small temperature changes in the PAB layer because it is protected by the HMA layer. UCPRC-RR

40 Depth (mm) Blow Counts PM 12.7 NB PM 12.4 NB PM 11.8 NB PM 11.4 NB PM 1.8 NB PM 1.2 NB PM 13. SB PM 12.7 SB PM 12.4 SB PM 12.1 SB PM 11.8 SB PM 11.4 SB PM 11.1 SB PM 1.8 SB PM 1.5 SB PM 1.2 SB HMA-AB Interface AB-SG Interface (a) Before construction Depth (mm) Blow Counts PM 12.7 NB PM 12.4 NB PM 11.8 NB PM 11.4 NB PM 1.8 NB PM 1.2 NB PM 13. SB PM 12.7 SB PM 12.4 SB PM 12.1 SB PM 11.8 SB PM 11.4 SB PM 11.1 SB PM 1.8 SB PM 1.2 SB HMA-PAB Interface PAB-SG Interface (b) After construction Figure 3.1: DCP test results of Alturas Project Section. 2 UCPRC-RR-28-15

41 1 Average NB Temperature = 37ºC; Average SB Temperature = 25ºC Control Section Modulus (MPa) 1 1 E_HMA_NB E_AB_NB E_SG_NB E_HMA_SB E_AB_SB E_SG_SB Postmile (mile) (a) Before rehabilitation 1 Average NB Temperature = 27ºC; Average SB Temperature = 22ºC Control Section Modulus (MPa) 1 1 E_HMA_NB E_PAB_NB E_SG_NB E_HMA_SB E_PAB_SB E_SG_SB Postmile (mile) (b) After rehabilitation Figure 3.2: Backcalculated moduli of Alturas Project Section before and after rehabilitation (21). UCPRC-RR

42 Average Morning(Mo) Temperature = 29ºC; Average Afternoon(Af) Temperature = 53ºC 1 Control Section Modulus (MPa) 1 1 E_HMA_Mo E_PAB_Mo E_SG_Mo E_HMA_Af E_PAB_Af E_SG_Af Postmile (mile) (a) Northbound lane Average Morning(Mo) Temperature = 2ºC; Average Afternoon(Af) Temperature = 5ºC 1 Control Section Modulus (MPa) 1 1 E_HMA_Mo E_PAB_Mo E_SB_Mo E_HMA_Af E_PAB_Af E_SG_Af Postmile (mile) (b) Southbound lane Figure 3.3: Backcalculated moduli of Alturas Project section (July 25). 22 UCPRC-RR-28-15

43 Average Morning(Mo) Temperature = 15ºC; Average Afternoon(Af) Temperature = 4ºC 1 Control Section Modulus (MPa) 1 1 E_HMA_Mo E_PAB_Mo E_SG_Mo E_HMA_Af E_PAB_Af E_SG_Af Postmie (mile) (a) Northbound lane Average Morning(Mo) Temperature = 24ºC; Average Afternoon(Af) Temperature = 42ºC 1 Control Section Modulus (MPa) 1 1 E_HMA_Mo E_PAB_Mo E_SG_Mo E_HMA_Af E_PAB_Af E_SG_Af PM (mile) (b) Southbound lane Figure 3.4: Backcalculated moduli of Alturas Project section (May 26). UCPRC-RR

44 Additional FWD tests were conducted in May 26, five years after construction. The tests were also carried out in both the morning and afternoon for evaluation at two different temperatures, as illustrated in Figure 3.4.The average backcalculated moduli of both the PAB and the AB were less than those in July 25. The possible reason is the seasonal variation of the modulus of the granular base material due to variable moisture content. Since May falls right after the rainy season in California, the moisture content of the PAB is probably greater than it is later in the summer. Temperature sensitivity effecting PAB stiffness was also not observed Pavement Condition Survey Results A pavement condition survey on the Alturas project section was performed in May 26, approximately five years after construction. Major load-related distresses were not observed. However, a few longitudinal cracks, a transverse crack, and raveling were observed as shown in Figure 3.5. Figure 3.5: Alturas Project section pavement condition pictures (May 26). As pictured, longitudinal cracks do not occur on the wheelpath, a fact that implies non-load related cracking. A possible reason for longitudinal cracking is a compaction problem along the longitudinal joint. The transverse crack might be the result of low-temperature cracking. However, rutting due to permanent 24 UCPRC-RR-28-15

45 deformation of the base layer was not observed.the most recent condition survey was performed in June 29, approximately eight years after rehabilitation. Photos from that survey are shown in Figure 3.6. The condition survey showed distresses in both the control section and the pulverization section as summarized in Table 3.1. It was particularly interesting to note the presence of longitudinal cracking in the outer wheelpaths of both directions that appeared to be construction joints because they were very straight and continuous, although the cracking was not aligned with the construction joints in the HMA. This indicates that these cracks may be due to low density in the wheeltracks of the pulverization machine. This occurs when a blade is not used on the initial compaction roller to redistribute material into those wheeltracks. Many cracks had been sealed, and sealant had been applied to raveling in the HMA, although this is not an appropriate maintenance technique. Some of the raveled areas appear to be marked for digouts, although there is no failure of the pavement in those locations other than the minor raveling as seen in Figure 3.6b. Overall, after eight years the pulverization section is showing the beginnings of fatigue cracking in the wheelpaths, as well as some distresses in the HMA due to the extremely low temperatures that occur at this location. The control section is showing similar distresses. The rutting is similar in both the control and pulverization sections, and is well below the failure threshold of 12.5 mm (1/2 in.). Table 3.1: Distress Observations at Alturas Project in June 29 Location Rut depths Distresses Observed (mm) PM 1.5 Control Section SB RWP: 7 A chip seal has been placed on this section. SB LWP: NB RWP: 9 Transverse cracks, longitudinal cracks, slight NB LWP: alligator cracks, raveling in wheelpaths PM 11.7 SB RWP: 6 SB LWP: NB RWP: 6 NB LWP: PM 16 SB RWP: 3 SB LWP: 5 NB RWP: 3 NB LWP: 5 PM 17 SB RWP: 3 SB LWP: 8 NB RWP: 6 NB LWP: 1 PM 2 SB RWP: 8 SB LWP: 4 NB RWP: 4 NB LWP: 6 Raveling, longitudinal cracking near wheelpath, slight alligator cracks Snow plow wear, longitudinal cracks near wheelpath intermittent. None Raveling, longitudinal cracks in wheelpath Note: SB = southbound, NB = northbound, RWP = right wheelpath, LWP = left wheelpath. UCPRC-RR

46 a. Typical conditions in control section. b. Typical conditions in cut areas of pulverization section. c. Typical conditions in fill areas of pulverization section. Figure 3.6: Pavement condition picture from Alturas Project (May 29). 3.2 Beckwourth Project Section Dynamic Cone Penetrometer Test Results DCP testing was conducted between PM-81 and PM-83 in July 25, as shown in Figure 3.7. In the figure, EB denotes the eastbound land and WB the westbound land. Based on the DCP test results, the moduli were calculated and are presented in the summary in Section UCPRC-RR-28-15

47 Blow Counts PM 81. EB Depth (mm) PM 81.5 EB PM 82. EB PM 82.5 EB PM 81.5 WB PM 82. WB PM 82.5 WB PM 83. WB HMA & PAB Interface PAB & SG Interface 12 Figure 3.7: DCP test results of Beckwourth Project section (July 25) Falling Weight Deflectometer Test Results After pulverization rehabilitation in 23, FWD testing was carried out in July 25, two years after construction. Tests were conducted between PM-81 and PM-83, in both morning and afternoon. Backcalculated moduli are shown in Figure 3.8. Moduli of the pulverized base and the subgrade layer did not change as temperatures changed from morning to afternoon. This finding implies that the stiffness of the pulverized material is not affected by temperature change despite the fact that many portions of the pulverized material contain broken HMA Pavement Condition Survey Results A pavement condition survey on the Beckwourth pilot project section was conducted in July 25, approximately two years after construction. Although some bleeding and skid marks were observed, major distresses were not found. A picture showing the pavement condition at that time is presented in Figure 3.9. The most recent condition survey of the Beckwourth project was performed in March 29, approximately six years after construction. The survey identified a few random cracks and a transverse crack just beginning (not extending all the way across both lanes yet), likely due to low-temperature cracking in the HMA. There is also some raveling which appears to be due to snow plowing. Photos from that survey are shown in Figure 3.1. UCPRC-RR

48 Average Morning(Mo) Temperature = 25ºC; Average Afternoon(Af) Temperature = 46ºC 1 1 Modulus (MPa) 1 E_HMA_Mo E_PAB_Mo E_SG_Mo E_HMA_Af E_PAB_Af E_SG_Af Postmile (mile) (a) Eastbound lane Average Morning(Mo) Temperature = 3ºC; Average Afternoon(Af) Temperature = 46ºC 1 1 Modulus (MPa) 1 E_HMA_Mo E_PAB_Mo E_SG_Mo E_HMA_Af E_PAB_Af E_SG_Af Postmile (mile) (b) Westbound lane Figure 3.8: Backcalculated moduli of Beckwourth Project section (July 25). 28 UCPRC-RR-28-15

49 Figure 3.9: Pavement condition picture on Beckwourth Project (July 25). Figure 3.1: Pavement condition picture from Beckwourth Project (March 29). 3.3 Poison Lake Project Section Dynamic Cone Penetrometer Test Results DCP tests were carried out both before and after rehabilitation in order to estimate the thickness of each layer, as shown in Figure The data showed that penetration blow counts before rehabilitation were typically greater than those after rehabilitation. This could indicate that the material was stiffer after construction. UCPRC-RR

50 Depth (mm) Depth (mm) Blow Counts (a) Before Rehabilitation (June 24) Blow Counts PM 12. WB PM 11.9 WB PM 11.8 WB PM 11.6 WB PM 11.5 WB PM 11.4 WB PM 11.2 WB PM 11. WB PM 1.8 WB PM 1.6 WB HMA-AB Interface AB-SG Interface PM 12. WB PM 11.9 WB PM 11.8 WB PM 11.6 WB PM 11.5 WB PM 11.4 WB PM 11.2 WB PM 11. WB PM 1.8 WB PM 1.6 WB HMA-PAB Interface PAB-SG Interface (b) After Rehabilitation (July 25) Figure 3.11: DCP Test Results Before and After Rehabilitation. 3 UCPRC-RR-28-15

51 3.3.2 Falling Weight DeflectometerTest Results FWD tests were carried out on the Poison Lake test section twice after construction. The first of these FWD tests were conducted in July 25, a year after construction, and the backcalculated moduli resulting are shown in Figure Testing was only carried out on the westbound lane due to traffic safety concerns. Subgrade moduli were greater than those of the other projects. 1 Average Morning(Mo) Temperature = 34ºC; Average Afternoon(Af) Temperature = 53ºC Modulus (MPa) 1 1 E_HMA_Mo E_PAB Mo E_SG Mo E_HMA_Af E_PAB_Af E_SG_Af Postmile (mile) Figure 3.12: Backcalculated moduli of Poison Lake Project section after rehabilitation (July 25) (Note: westbound lane only). Additional FWD testing was performed in May 26, two years after rehabilitation. Unlike the earlier Poison Lake FWD testing, tests were carried out in both the eastbound and westbound lanes. In order to find the spatial variability of the backcalculated moduli, FWD tests were conducted from PM- to PM-12. The test results revealed spatial variability to be insignificant in the backcalculated moduli (see Figure 3.13) in this subsection of the overall project. Additional compaction due to traffic and the development of suction after initial construction are possible explanations for the greater average stiffness found in May 26 than in July 25. UCPRC-RR

52 Average Morning(Mo) Temperature = 15 ºC; Average Afternoon(Af) Temperature = 4 ºC 1 Modulus (MPa) 1 1 E_HMA_Mo E_PAB_Mo E_SG_Mo E_HMA_Af E_PAB_Af E_SG_Af Postmile (mile) (a) Westbound Average Morning(Mo) Temperature = 25 ºC; Average Afternoon(Af) Temperature = 41 ºC 1 Modulus (MPa) 1 1 E_HMA_Mo E_PAB_Mo E_SG_Mo E_HMA_Af E_PAB_Af E_SG_Af Postmile (mile) (b) Eastbound Figure 3.13: Backcalculated moduli of Poison Lake Project section (May 26). 32 UCPRC-RR-28-15

53 3.3.3 Pavement Condition Survey Results A pavement condition survey on the Poison Lake Pilot Project section was conducted in May 26, approximately two years after construction. No pavement distress was observed. The most recent condition survey was performed in May 29, approximately five years after construction. The distresses observed are shown in Table 3.2. Figure 3.14 shows photos of the pavement at several locations. The results show extensive cracking in the wheelpaths. Many of the wheelpath cracks have been sealed, but additional ones have appeared since the last time sealant was applied, as can be seen in Figure 3.14b. In addition, there is longitudinal cracking similar to that seen in Alturas, also possibly due to lack of compaction in the wheelpaths of the pulverization machine. The longitudinal cracking does not appear to be aligned with the HMA longitudinal construction joints. Overall, the condition survey indicates that the Poison Lake Project is underdesigned for fatigue cracking of the HMA, since the 1-year design has significant fatigue cracking in the wheelpaths after only five years. It is not known at this time how well compacted the HMA is, or its fatigue resistance relative to other mixes used in the district, which are factors that may be contributing to the early appearance of fatigue cracking. On the other hand, there rutting is well below the failure limit of 12.5 mm. Table 3.2: Distress Observations at Poison Lake Project in June 29 Location Rut Depths Distresses Observed (mm) PM 4 EB RWP: 2 EB LWP: 2 WB RWP: 3 WB LWP: 3 Alligator cracks in both wheelpaths, longitudinal crack between wheelpaths PM 1.5 EB RWP: 2 EB LWP: 2 WB RWP: 2 WB LWP: PM 13.1 EB RWP: EB LWP: WB RWP: 3 WB LWP: Alligator cracks in both wheelpaths, longitudinal crack between wheelpaths Alligator cracks in both wheelpaths intermittent, longitudinal crack between wheelpaths, some transverse cracks between wheelpaths do not appear to be temperature related Note: EB = eastbound, WB = westbound, RWP = right wheelpath, LWP = left wheelpath. UCPRC-RR

54 a. Typical cracking. b. Wheelpath crack and rut details. Figure 3.14: Pavement condition pictures from Poison Lake Project (June 29). 3.4 Cayton Creek Project Section A pavement condition survey on the Cayton Creek Project section was conducted in June 29, approximately three years after construction. Results of the condition survey are shown in Table 3.3. Photos from that survey are shown in Figure The condition survey showed no cracking after three years. There is minimal rutting in the climbing lane where there is a 6.5 percent grade (PM 36.7). There is more rutting in a flat section (PM 42.7). There is some raveling of the HMA surface including some popouts of large aggregates. Table 3.3: Distress Observations at Cayton Creek Project in June 29 Location Rut Depths Distresses Observed (mm) PM 36.7 SB RWP: SB LWP: 3 NB RWP: NB LWP: 3 Raveling: Some paving segregation in HMA surface, some large stones plucked from surface. PM 42.7 SB RWP: SB LWP: 8 NB RWP: 8 NB LWP: 8 Raveling: Some paving segregation in HMA surface, some large stones plucked from surface. Intermittent postconstruction grinding. Note: SB = southbound, NB = northbound, RWP = right wheelpath, LWP = left wheelpath. 34 UCPRC-RR-28-15

55 a. Typical condition in flat section. b. Typical condition in climbing section with 6.5 percent grade. Figure Pavement condition pictures from Cayton Creek Project (June 29). 3.5 Field Relative Density and R-Value Field measurements of relative compaction using a nuclear gauge (CTM-231) and the R-value test using a stabilometer (CTM-31) were conducted by the Caltrans District 2 laboratory, who also checked quality control during the construction. The minimum requirements for relative compaction (RC) of the Caltrans (CTM-216) method and R-value are 95 percent and 78, respectively. The test results are summarized in Table 3.4. UCPRC-RR

56 Field RC R-value a Stdev = Standard Deviation b NA = Not Available Table 3.4: Field Relative Compaction and R-Value Alturas Beckwourth Poison Lake Cayton Creek Mean NA b Stdev a Mean Stdev a NA b NA b The results indicated that field relative compactions and R-values generally met their respective specifications and the variability is not significant. However, the R-value of the Beckwourth PAB barely met the minimum value in the specification of 78. This implies that the strength or the structural capacity of the Beckwourth pulverized material could be inferior to the other PABs. 3.6 Summary of Field Results Stiffness Results Based on the DCP test results, the moduli were calculated using the three equations presented in Chapter 2. The calculated moduli are summarized in Table 3.5. Table 3.5: Summary of the Moduli Calculated from DCP Test Results E a eff (MPa) E b (MPa) E c (back) (MPa) Project Material Time Mean Stdev Mean Stdev Mean Stdev AB Before PAB After Alturas Before SG After PAB Beckwourth After SG AB Before PAB After Poison Lake Before SG After Cayton AB Before Creek SG a ( log( DN )) E eff ( MPa) = 1 b ( ). 64 E ( MPa) = / DN c. 39 ( ) E back ( MPa) = 338 DN 36 UCPRC-RR-28-15

57 Average moduli (E eff ) calculated by the equation proposed by CSIR (12) are generally the largest, whereas those proposed by Jianzhou (14) are the smallest. DCP-calculated moduli of SG are greater after construction because additional densification was obtained from compaction of the upper layer during construction. Based on the backcalculation of FWD tests on pilot project sections, the backcalculated moduli of PAB are summarized in Table 3.6. Table 3.6: Summary of Backcalculated Moduli of PAB Schedule Unit (MPa) Alturas Beckwourth Poison Lake AB PAB PAB PAB September Mean Standard Deviation July 25 Mean Standard Deviation May 26 Mean Standard Deviation In order to evaluate the differences between DCP-calculated modulus using the various equations and backcalculated moduli of PAB, the relationship between average backcalculated modulus and DCPcalculated modulus is illustrated in Figure The results indicate that the moduli calculated by the equation proposed by Jianzhou (14) are the closest to the backcalculated moduli. 12 DCP-Calculated Modulus (MPa) CSIR Equation (1997) Chai and Roslie Equation (1998) Jianzhou Equation (1999) Backcalculated Modulus (MPa) Figure 3.15: Comparison of backcalculated modulus with DCP-calculated modulus. UCPRC-RR

58 Conclusions based on these results are summarized as follows: Average backcalculated moduli of the pulverized materials from all three projects for which results are available were all greater than those of the typical virgin aggregate base material at the Alturas project section. Although the test results were compared with only one typical aggregate material in one specific pavement structure, they support that the pavement structure with pulverized materials can generally reduce the elastic deformation and the stresses that cause rutting in the unbound layers. Temperature sensitivity of the pulverized material was investigated based on the comparison of the backcalculated moduli of PAB at two different temperatures in most of the FWD testing because the pulverized HMA is between 6 and 85 percent by mass of the PAB, although bonds between particles are broken by pulverization. Since HMA is a viscoelastic material, the modulus of HMA is significantly affected by temperature change. However, temperature sensitivity of the PAB was not observed during all FWD testing. This might be in part due to the smaller temperature changes in the PAB layer because it is protected by an HMA layer. It may also be due to the previous aging of the asphalt in the PAB, which would make it less susceptible to temperature changes, and to the granular nature of the PAB. It was found that the stiffness of the PAB generally increased with time after construction. This might be due to the pulverized material attaining greater stiffness due the additional compaction resulting from traffic. Cosentino et al. (27) also found that the stiffness of the PAB (referred to as recycled asphalt pavement [RAP] in that report) increased throughout an eight-week study period based on field measurements. The exception was the last set of FWD measurements taken on the Alturas project, which showed a decrease. However, those measurements may reflect seasonal variability, since they were taken in May, soon after the end of the wet/freeze season, whereas previous measurements were taken in July and September Condition Survey Results Conclusions based on the condition survey results are summarized as follows: Rutting appears to not be a problem on any of the four projects, with maximum rut depths on the order of 6 mm (1/4 in.). Without trenching it is uncertain how much of the observed rutting is in the HMA and how much is in the pulverized base and subgrade. The oldest project, at Alturas, is just beginning to show fatigue cracking in the wheelpath after eight years in service. On the other hand, the Poison Lake project is showing extensive fatigue cracking in the wheelpaths after only five years of service. The fatigue properties and compaction of the HMA at Poison Lake relative to that of the other projects is not known. The two projects at 38 UCPRC-RR-28-15

59 Beckwourth and Cayton Creek have no fatigue cracking after six and three years of service, respectively. The Alturas and Poison Lake Projects both show extensive longitudinal cracking, which is in or near the wheelpaths, but which appears to be construction-related because the cracks are very straight and continuous. These cracks may be related to the pulverization machine s wheelpaths, which may not have been filled in by a blade during initial compaction. UCPRC-RR

60 4 UCPRC-RR-28-15

61 4 LABORATORY TEST RESULTS 4.1 Index Test Results Particle Size Distribution Sieve analyses of the Alturas and Beckwourth PAB and District 2 Class 2 AB were conducted, and the results are shown in Figure 4.1. For the two pulverized materials (PABs), only dry sieving using ASTM C136 was carried out to determine the particle size distribution of the larger aggregates. On the other hand, both ASTM C117 and ASTM C136 which provide a method for determining the amount of material finer than 75 μm (#2 sieve) in the aggregate by washing were used for District 2 Class 2 aggregate base (AB). Percent passing Alturas PAB Caltrans Class 2 AB Spec Beckwourth PAB District 2 Class 2 AB Sieve Size (mm) Figure 4.1: Gradations of Alturas and Beckwourth PAB (dry sieve only), District 2 Class 2 AB (dry and wet sieve) and Caltrans gradation requirements. As shown in Figure 4.1, the gradation of the Alturas and Beckwourth pulverized material generally met the requirements for Caltrans Class 2 AB material, except for the small particle sizes. For the small particle sizes, the gradation might be within the specification range because only dry sieving (ASTM C117) was conducted. To determine the percentage of passing small particles, ASTM C136 is required since the finer materials can adhere to the larger particles and therefore cannot pass the sieve by dry sieving. The gradation of District 2 Class 2 AB was finer than the specification for the coarse fraction. UCPRC-RR

62 In order to find the gradation variability of the pulverized material, sieve analyses were conducted on material from thirty different locations in the Poison Lake section and twenty different locations in the Cayton Creek project section. To determine the effect of variability of the gradation on performance, three representative gradations were selected for additional testing. The three gradations were mean (Medium gradation), mean+2 standard deviations (Fine Gradation), and mean-2 standard deviations (Coarse Gradation) according to each size fraction. The thirty gradations and the three representative gradations of the Poison Lake PAB are shown in Figure 4.2. Only dry sieving (ASTM C136) was performed to obtain these gradations of the Poison Lake pulverized material. The pulverized materials in the Cayton Creek project were sampled at twenty different locations, and ASTM-C117 and ASTM-C136 were conducted together. The gradations from twenty different locations and three representative gradations are shown in Figure 4.3. The results indicate that the pulverized material from the Cayton Creek project generally met the requirements for Caltrans Class 2 AB material, except for the largest (25 mm and 19 mm sieve) and the smallest (75 μm sieve) particle sizes. Several researchers (28, 29, 3) reported that high fines contents generally lead to a lower resilient modulus and reduced permanent deformation resistance of the virgin aggregate material Atterberg Limits Testing Based on the results of Atterberg limits testing, all the pulverized materials were classified as non-plastic, as expected considering that the parent material is primarily HMA Compaction Testing Compaction tests were conducted using ASTM Standard (D698), ASTM Modified (D1557), and Caltrans (CTM-216) methods to find the maximum dry density and the optimum moisture content. Compaction tests were conducted for four different PABs from the pilot project sections, and Class 2 aggregate base material from Districts 4 and 2. For the pulverized material from the Alturas project, only the Caltrans compaction method was carried out due to a shortage of material. In order to evaluate the effect of different gradations on the density of the pulverized material, compaction tests with three different gradations were performed on the pulverized material from the Cayton Creek Project. The compaction test results are presented in Figure UCPRC-RR-28-15

63 1 9 8 Percent Passing Sieve Size (mm) (a) Gradations of 3 different locations Percent Passing Coarse Gradation Fine Gradation Medium Gradation Caltrans Class 2 AB Spec Sieve Size (mm) (b) Three representative gradations Figure 4.2: Gradations of thirty different locations and three representative gradations of pulverized material from Poison Lake Project. UCPRC-RR

64 1 9 8 Percent Passing Sieve Size (mm) (a) Gradations of 2 different locations Percent Passing Caltrans Class 2 AB Spec Mean (Medium Gradatoin) Mean + 2s (Fine Gradation) Mean - 2s (Coarse Gradation) Sieve Size (mm) (b) Three representative gradations Figure 4.3: Gradations of twenty different locations and three representative gradations of the pulverized material from Cayton Creek Project. 44 UCPRC-RR-28-15