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Author: Shawn Shiangfeng Hung
Publisher:
ISBN: 9781085585194
Category :
Languages : en
Pages :
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Book Description
The pavement community, including both agencies and industries, is moving toward more sustainable pavement designs and pavement network management. Increasing amounts of recycled materials, both reclaimed asphalt pavement (RAP) and recycled tire rubber, are expected to be used in new pavement construction projects in the future to reduce the use of virgin binder and aggregates. The main concern of using recycled materials in new asphalt pavement is the potential negative effect on the performance. Thus, the primary objective of this dissertation is to improve the current laboratory testing technologies and performance assessment approaches for characterizing the performance-related properties of asphalt mixes containing recycled materials and to improve understanding of how these properties affect the performance of asphalt pavements so that they can be designed and constructed better. A major challenge regarding the use of high RAP content mixes is the differences in the rheological properties of the virgin binder (mixes without RAP) and the blended binder (mixes with RAP). Traditionally, binder blending charts are used to determine the appropriate RAP content in asphalt mixes and the selection of virgin binder grade as part of the Superpave volumetric mix design procedures when RAP is incorporated in the mix. However, producing mixes based on blending charts that require testing of extracted and recovered RAP binders is expensive and hazardous. An alternative test approach for binder blending charts using fine aggregate matrix (FAM) mix testing is presented in this dissertation. The results demonstrated that the proposed approach could estimate the blended binder intermediate and low performance grading temperatures within ±3°C of the measured blended binder performance grading temperatures. Even though the proposed approach is not as accurate as the blending chart method (within ±2°C), it provides both cost and environmental benefits. Currently, the Superpave Performance Grading (PG) system cannot not be used to evaluate the performance-related properties of asphalt rubber binders produced using larger crumb rubber particles (maximum particle size passing 2.36 mm sieve) due to the limitations of parallel plate geometry. With the consideration of more open-graded or gap-graded rubberized hot mix asphalt (RHMA-O and RHMA-G) projects in the future, it is important to be able to perform Superpave PG testing on asphalt rubber binder and to establish performance-based contract acceptance criteria for the production of asphalt rubber binders. The test results indicated that the concentric cylinder geometry is an appropriate alternative geometry to parallel plates for quantifying the properties of asphalt rubber binders and specifically for assessing the high-temperature performance properties of binders containing crumb rubber particles larger than 250 [mu]m. Concerns have been raised with regard to incorporating reclaimed rubberized asphalt pavement (RRAP) into dense-graded new hot mix asphalt (HMA-DG) and RAP into new RHMA-G since the interactions between the virgin binder, age-hardened binder, and recycled tire rubber could considerably affect the rutting, fatigue cracking, and thermal cracking performances of new HMA-DG and RHMA-G. The fundamental differences between RAP and RRAP were identified and the performance of new mixes that contain these recycled materials were evaluated in this study. The experimental results showed that adding RRAP to HMA-DG mixes is ideal to resist rutting and low-temperature cracking based on the changes in mix stiffness. The HMA-DG mixes containing RRAP are better at resisting high tensile strain loadings than mixes containing RAP. In addition, adding RAP to RHMA-G mixes improves the rutting performance but diminishes the cracking performance, and potentially negating the benefits of selecting RHMA-G as an overlay to retard the rate of reflection cracking. Lastly, the effects of rest periods on asphalt fatigue performance considering asphalt thixotropy, non-linearity, self-heating, self-cooling, and steric hardening were also investigated in this research. The experimental test results showed that asphalt thixotropic softening and other biasing effects control the first 10 to 15 percent decrease in stiffness for unmodified binders and 15 to 35 percent decrease in stiffness for modified binders under cyclic loading, and this decrease in stiffness can be recovered with the introduction of rest periods. This means that most of the repeated loadings applied to test specimens within the thixotropic softening range do not caused any fatigue damage but only softening of the materials. Thus, by providing sufficient rest periods within the thixotropic softening range can effectively improve asphalt fatigue performance. Both the thixotropic softening range and the required time for thixotropic recovery (i.e., rest periods) need to be considered in asphalt fatigue test and mechanistic-empirical (ME) design for better evaluation of the true fatigue performance.
Author: Shawn Shiangfeng Hung
Publisher:
ISBN: 9781085585194
Category :
Languages : en
Pages :
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Book Description
The pavement community, including both agencies and industries, is moving toward more sustainable pavement designs and pavement network management. Increasing amounts of recycled materials, both reclaimed asphalt pavement (RAP) and recycled tire rubber, are expected to be used in new pavement construction projects in the future to reduce the use of virgin binder and aggregates. The main concern of using recycled materials in new asphalt pavement is the potential negative effect on the performance. Thus, the primary objective of this dissertation is to improve the current laboratory testing technologies and performance assessment approaches for characterizing the performance-related properties of asphalt mixes containing recycled materials and to improve understanding of how these properties affect the performance of asphalt pavements so that they can be designed and constructed better. A major challenge regarding the use of high RAP content mixes is the differences in the rheological properties of the virgin binder (mixes without RAP) and the blended binder (mixes with RAP). Traditionally, binder blending charts are used to determine the appropriate RAP content in asphalt mixes and the selection of virgin binder grade as part of the Superpave volumetric mix design procedures when RAP is incorporated in the mix. However, producing mixes based on blending charts that require testing of extracted and recovered RAP binders is expensive and hazardous. An alternative test approach for binder blending charts using fine aggregate matrix (FAM) mix testing is presented in this dissertation. The results demonstrated that the proposed approach could estimate the blended binder intermediate and low performance grading temperatures within ±3°C of the measured blended binder performance grading temperatures. Even though the proposed approach is not as accurate as the blending chart method (within ±2°C), it provides both cost and environmental benefits. Currently, the Superpave Performance Grading (PG) system cannot not be used to evaluate the performance-related properties of asphalt rubber binders produced using larger crumb rubber particles (maximum particle size passing 2.36 mm sieve) due to the limitations of parallel plate geometry. With the consideration of more open-graded or gap-graded rubberized hot mix asphalt (RHMA-O and RHMA-G) projects in the future, it is important to be able to perform Superpave PG testing on asphalt rubber binder and to establish performance-based contract acceptance criteria for the production of asphalt rubber binders. The test results indicated that the concentric cylinder geometry is an appropriate alternative geometry to parallel plates for quantifying the properties of asphalt rubber binders and specifically for assessing the high-temperature performance properties of binders containing crumb rubber particles larger than 250 [mu]m. Concerns have been raised with regard to incorporating reclaimed rubberized asphalt pavement (RRAP) into dense-graded new hot mix asphalt (HMA-DG) and RAP into new RHMA-G since the interactions between the virgin binder, age-hardened binder, and recycled tire rubber could considerably affect the rutting, fatigue cracking, and thermal cracking performances of new HMA-DG and RHMA-G. The fundamental differences between RAP and RRAP were identified and the performance of new mixes that contain these recycled materials were evaluated in this study. The experimental results showed that adding RRAP to HMA-DG mixes is ideal to resist rutting and low-temperature cracking based on the changes in mix stiffness. The HMA-DG mixes containing RRAP are better at resisting high tensile strain loadings than mixes containing RAP. In addition, adding RAP to RHMA-G mixes improves the rutting performance but diminishes the cracking performance, and potentially negating the benefits of selecting RHMA-G as an overlay to retard the rate of reflection cracking. Lastly, the effects of rest periods on asphalt fatigue performance considering asphalt thixotropy, non-linearity, self-heating, self-cooling, and steric hardening were also investigated in this research. The experimental test results showed that asphalt thixotropic softening and other biasing effects control the first 10 to 15 percent decrease in stiffness for unmodified binders and 15 to 35 percent decrease in stiffness for modified binders under cyclic loading, and this decrease in stiffness can be recovered with the introduction of rest periods. This means that most of the repeated loadings applied to test specimens within the thixotropic softening range do not caused any fatigue damage but only softening of the materials. Thus, by providing sufficient rest periods within the thixotropic softening range can effectively improve asphalt fatigue performance. Both the thixotropic softening range and the required time for thixotropic recovery (i.e., rest periods) need to be considered in asphalt fatigue test and mechanistic-empirical (ME) design for better evaluation of the true fatigue performance.
Author: National Research Council (U.S.). Transportation Research Board
Publisher: Transportation Research Board National Research
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 60
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Book Description
Author: Harikrishnan Nair
Publisher:
ISBN:
Category : Asphalt concrete-Additives
Languages : en
Pages : 0
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Book Description
Ground tire rubber (GTR) from scrap tires is used in asphalt mixtures (rubber modified asphalt [RMA]) for improving the performance of pavements. There are different ways to add GTR in asphalt mixtures, but the two primary methods are referred to as the “wet” and “dry” processes. The dry process incorporates GTR directly into the asphalt mixture during production (directly to the aggregates through the reclaimed asphalt pavement collar). The Virginia Department of Transportation (VDOT) has limited experience with RMA mixtures in Superpave dense-graded mixtures using the dry process, but the relative ease of mixture production makes the dry process an attractive option for RMA. In the fall of 2019, VDOT placed a dense-graded RMA mixture, SM 12.5 (GTR), on US 60 in VDOT’s Richmond District (New Kent County). This was the first use of a SM 12.5 (GTR) mixture in Virginia using the dry process method. The purpose of this study was to establish a performance baseline for a GTR modified dense-graded asphalt mixture that was designed and produced using the dry process. The US 60 project also included the use of a thin hot mix asphalt concrete overlay (THMACO) as an interlayer. An assessment of the THMACO as an interlayer was a secondary objective of the study. The study found that dry process SM 12.5 (GTR) mixture can be produced and placed with no significant field-related concerns and that the special provision developed for its use was effective. Density requirements were achieved, and the as-placed mat had excellent (very low) permeability characteristics. Laboratory performance testing showed the SM 12.5 (GTR) mixture to be more crack resistant than conventionally modified polymer (SM 12.5E) mixtures. Conventionally modified SM E mixtures had slightly better rutting performance. However, this conclusion was based on performance testing and thresholds that were developed for non-modified asphalt mixtures. Additional laboratory and field performance comparison is needed to develop mixture acceptance criteria for GTR mixtures. Further, THMACO mixtures had excellent laboratory reflective cracking resistance properties. They performed particularly well in the Texas overlay test. Grading of extracted (from the asphalt mixture) binder may not provide an accurate representation of the binder performance for the dry process GTR modified asphalt. Continued monitoring of performance will be needed to quantify any benefit of SM 12.5 (GFR) mixtures in comparison with regular SM E mixtures. The study recommends additional field trials with SM 12.5 (GTR) mixtures for performance evaluation. Further, the study recommends continued use of a THMACO as an interlayer to mitigate reflective cracking for composite pavements.
Author: Carl L. Monismith
Publisher: McGraw-Hill Companies
ISBN: 9780070429833
Category : Technology & Engineering
Languages : en
Pages : 480
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Book Description
Focusing on asphalt paving technology, this work emphasizes quality control and quality assurance programmes in producing high-quality pavements. It combines theory and practice of asphalt paving including developments and information from the recently completed Strategic Highway Research Program which was designed to improve asphalt specifications, mix design and analysis systems.
Author: Randy Clark West
Publisher: Transportation Research Board
ISBN: 0309259134
Category : Pavements, Asphalt
Languages : en
Pages : 162
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Book Description
TRB's National Cooperative Highway Research Program (NCHRP) Report 752: Improved Mix Design, Evaluation, and Materials Management Practices for Hot Mix Asphalt with High Reclaimed Asphalt Pavement Content describes proposed revisions to the American Association of State Highway and Transportation Officials (AASHTO) R 35, Superpave Volumetric Design for Hot Mix Asphalt, and AASHTO M 323, Superpave Volumetric Mix Design, to accommodate the design of asphalt mixtures with high reclaimed asphalt pavement contents.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Abstract : The accumulation of waste tires generates severe environmental issues. Using crumb rubber processed from waste tires on the pavement could relieve the pressure of waste tire on the environment and improve the performance of the pavement as well. The application of crumb rubber on the pavement using the dry process was proved to be a cost-effective strategy in some projects, however, the interaction between the rubber and asphalt binder was unknown in the rubber modified asphalt mixture using the dry process, especially when reclaimed asphalt pavement was adopted. The performance improvement of the rubber particle to the asphalt mixture was closely related to the interaction. The influence of aging on the characteristics of rubber modified asphalt mixture using the dry process is critical to its long-term performance. The scope of the dissertation is to evaluate the performance of rubber modified asphalt mixture using a dry process when reclaimed asphalt pavement was adopted. The influence of aging on the characteristics of the rubber modified asphalt mixture and the extracted asphalt binder were investigated. This dissertation proposed the volumetric design of rubber modified asphalt mixture using the dry process. The aggregate gradation determination, rubber modified asphalt mixture preparation, design binder content determination, and moisture susceptibility evaluation were proposed. The quality control of the laboratory mixture design procedure was critical to guarantee the consistency of the asphalt mixture design in the laboratory and the results of mixture construction in the plant. The high temperature rutting performance and the low temperature cracking performance of plant mixed and laboratory compacted asphalt mixture was evaluated. The influence of various factors, which included mixture design parameters of the asphalt mixture (nominal maximum aggregate size, reclaimed asphalt pavement content, and asphalt content), rubber modification, mixture air void content, test temperature, and aging procedure, on the rutting and low temperature characteristics of asphalt mixtures were evaluated. Based on the evaluation of different assessment parameters, the rubber addition and the rubber addition and aging were the two most critical factors that influenced the rutting and low temperature cracking performance of different asphalt mixtures. The effect of the Trichloroethylene solvent in asphalt binder was investigated, and the extracted asphalt binder was assessed and compared with the base asphalt binder and rubber modified base asphalt binder. Both the existence of Trichloroethylene and the content of Trichloroethylene had a significant influence on the |G*| of unaged and PAV aged asphalt binder. The Trichloroethylene in the extracted asphalt binder significantly influenced the actual performance of the asphalt binder in the reclaimed asphalt binder, thus potentially compromising the success mixture design. The modified extraction procedure was proposed to improve the accuracy of the extraction procedure. The rubber particles in the asphalt mixture using the dry process were not totally interacted with asphalt binder, only the interacted rubber particles were extracted, and the influence of the interacted rubber particle was assessed. The aged asphalt binder weakened the low temperature performance of the extracted asphalt binder. The aged asphalt binder and rubber in extracted asphalt binder guaranteed the asphalt binder to sustain heavy traffic load, thus improved the permanent deformation resistance of asphalt binder.
Author: Hawraa Kadhim
Publisher:
ISBN:
Category : Asphalt pavements
Languages : en
Pages : 17
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Book Description
The use of reclaimed asphalt pavement (RAP) in hot mix asphalt (HMA) has been increasing in the last few decades because of its cost benefits and because of a compelling need to preserve the environment and natural resources. It is commonly assumed that HMA containing RAP (HMA-RAP) has an improved resistance to permanent deformation (rutting) and decreased resistance to the fatigue cracking. This is due to the fact that asphalt binder contained in the RAP has been oxidized over the years and is typically stiffer than virgin asphalt binder. However, during the production stage of the HMA-RAP, the blending between aged and virgin asphalt binders would be incomplete or partial, which would lead to heterogeneous distribution of the aged and virgin asphalt binders within the asphalt mix with RAP. Therefore, the purpose of this article is to evaluate the effect of silo storage on the blending mechanism between virgin and RAP asphalt binders and the impact that this would have on performance of the mix. Two plant-produced asphalt mixes (HL-3 and HL-8), typically used in the province of Ontario for surface and base courses in flexible pavements, were considered in this study. The mixes were designed with 15 and 30 % RAP, respectively, and the samples were collected immediately after the production (0 h) or at different silo storage times (1, 4, 8, and 12 h). The temperatures of the collected materials were closely monitored and recorded. The findings of this research indicated that silo-stored samples exhibited some improvement in their rutting and fatigue resistance. The examination of the dynamic modulus master curves indicated that the rheology of the mixes evolved with silo storage and that blending between the aged and the virgin binders has been improved.
Author:
Publisher:
ISBN:
Category : Asphalt
Languages : en
Pages : 112
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Book Description
TRB's Transportation Research Record (TRR): Journal of the Transportation Research Board, No. 2445 consists of 12 papers that examine the low-temperature characterization of foamed warm-mix asphalt produced by water injection; an analytical methodology to determine the composition of filler used in hot-mix asphalt; effects of binder modification on aggregate structure and thermovolumetric properties of asphalt mixtures; and a statistical analysis of the influence of mix design parameters on mechanical properties of mixes with reclaimed asphalt pavement. This issue also explores new additives for use in hot in-place recycling to improve performance of reclaimed asphalt pavement mix; the effect of crumb rubber dissolution on low-temperature performance and aging of asphalt-rubber binder; laboratory investigation of biochar-modified asphalt mixture; and a laboratory study on effects of high reclaimed asphalt pavement and binder content, which include stiffness, fatigue resistance, and rutting resistance. Additionally, this TRR explores the production, construction, and properties of high reclaimed asphalt pavement mixtures; strategies for incorporating higher recycled asphalt pavement percentages; the laboratory performance of asphalt mixtures containing recycled asphalt shingles; and testing of fine asphalt mixtures to quantify effectiveness of asphalt binder replacement using recycled shingles.
Author: Hamza Alkuime
Publisher:
ISBN:
Category : Pavements, Asphalt
Languages : en
Pages : 626
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Book Description
Asphalt mixes are designed to provide adequate resistance to various distresses including cracking, rutting, and moisture damage. Recently, more efforts are directed towards including performance assessment tests during the design and production of asphalt mixes. Performance-Engineered Mix Design (PEMD) or Balanced Mix Design (BMD) is a new and innovative design approach that incorporates performance assessment tests to optimize the design of asphalt mixes to provide adequate performance. Although transportation agencies are motivated to implement the PEMD approach, several research knowledge gaps and concerns need to be addressed before PEMD successful implementation. This research study aims to advance, develop, and implement performance-engineered design approach and specifications to extend the service life of asphalt pavements.The first phase of this research developed and evaluated a new and innovative monotonic cracking performance indicator called Weibull Cracking Resistance Index (WeibullCRI). The proposed indicator describes the entire load-displacement curve, which overcomes the limitations of the existing performance indicators. First, WeibullCRI was examined using an extensive laboratory evaluation of 16 different asphalt mixes. The results indicated that WeibullCRI was sensitive to variation in binder content and binder PG and the results were in good agreement with the expected cracking resistance based on the composition of the studied mixes. In addition, WeibullCRI had low variability in test results and higher number of various statistical groups. Next, the applicability of WeibullCRI as a unified approach to analyze the results of various monotonic assessment tests was investigated using data generated by other researchers and reported in the literature. The results indicated that WeibullCRI is able to interpret the testing results of various monotonic performance assessment tests (i.e., IDT- intermediate temperature, Semi-Circle Bending [SCB]- intermediate temperature, SCB-low temperature, Disk-Shaped Compact Tension [DCT], and Simple Punching Shear Test [SPST]) and various displacement measurement methods (i.e., actuator vertical displacement and Crack Mouth Opening Displacement [CMOD]). WeibullCRI was also sensitive to variation in test conditions (i.e., specimen notch depth, thickness, and air void content) and mix composition proportions (i.e., binder content, binder grade, aggregate type, NMAS, aging, rejuvenator dosages, and Recycled Asphalt Pavement [RAP] materials).The second phase of this study reviewed and evaluated the current monotonic cracking performance assessment tests and indicators including the developed WeibullCRI used to assess asphalt mix resistance to cracking. In this phase, the testing requirements of various test standards, key publications, concepts, calculation methods, physical meaning, and advantages and disadvantages of various performance indicators were reviewed. Then, the study investigated the validity of the most promising testing standards and indicators. Three testing standards and 12 performance indicators were considered. Several aspects were examined including 1) investigate the fundamental meaning of the variation in the load-displacement curve in terms of the change in mix resistance to cracking, 2) sensitivity of performance indicators to mix compositions, 3) variability in test results, 4) number of various statistical groups, 5) correlation between various performance indicators, 6) direct correlation between laboratory results of monotonic performance tests and indicators with the observed field cracking, and 7) ability to develop PEMD specifications. A comprehensive laboratory investigation was conducted using 33 different asphalt mixes included six Laboratory Mixed-Laboratory Compacted (LMLC) and 10 Plant Mixed-Laboratory Compacted (PMLC) asphalt mixes, and 17 field projects with known cracking performance. The results showed that WeibullCRI calculated from the IDT test to have the lowest test variability, maximum number of Tukey's honestly significant difference (HSD) groups, and have excellent correlation with cyclic cracking resistance assessment indicators as compared to the other monotonic performance indicators. In addition, the results demonstrated that there was no direct correlation between all monotonic performance indicators and the observed field cracking performance, therefore an alternative approach was proposed, evaluated, and validated to develop performance thresholds for the selected performance indicators. Three pass/fail cracking performance thresholds were proposed for WeibullCRI to distinguish between asphalt mixes with good, fair, and poor cracking resistance using the proposed approach.The third phase of this study focused on the development and evaluation of a new cyclic cracking assessment test called Multi-Stage Semi-circle bending Dynamic (MSSD). The test offers advantages over the available monotonic and dynamic cracking assessment tests and addresses major concerns to implement the PEMD (i.e., performance test validity, complex specimen preparation, and testing time). The developed MSSD test simulates the repeated loading (cyclic) in a reasonable testing time (less than 9 hours per test regardless of mix type), has a fixed loading sequence that works for mixes with different characteristics (e.g., mix composition, percent air void content, thickness, etc.), and utilizes testing equipment and specimen geometry similar to that used in monotonic tests. The laboratory evaluation results showed that the proposed test and its derived performance indicators were sensitive to mix composition and had lower variability compared to other dynamic tests. In addition, the MSSD performance indicators correlated well with the observed cracking performance in the field and were able to distinguish between projects with good and poor resistance to cracking. Based on the evaluation results, three pass/fail cracking performance thresholds were proposed to distinguish between asphalt mixes with good, fair, and poor resistance to cracking.The fourth phase of this research examined the most promising tests and performance indicators to evaluate the resistance of asphalt mixtures to rutting. Two tests (i.e., Hamburg Wheel Tracking test [HWTT], and Asphalt Pavement Analyzer [APA] rut test) and three rutting performance indicators (i.e., HWTT rut depth after 15,000 passes [HWTT15000], HWTT rut depth at 20,000 passes [HWTT20000], and APA rut depth after 8,000 cycles [APA8000]) were considered. An intensive laboratory investigation was conducted that included six LMLC, 10 PMLC, and field cores extracted from 17 field projects. The research findings showed that both HWTT and APA rut test provided similar rutting assessment for the evaluated mixes. The study recommended using the HWTT over the APA rut test since HWTT can be also used to assess the resistance of asphalt mixtures to moisture damage to moisture damage. Also, the study recommended using HWTT15000 over HWTT20000 as a performance indicator since it requires less testing time.The final phase of this research provided recommendations of the best testing standards, performance indicators, and performance specifications to assess asphalt mix resistance to cracking and rutting. In addition, it provided guidelines to demonstrate the use of the proposed tools during the design and/or production of asphalt mixes. It also proposed standards testing procedures for the newly developed WeibullCRI performance indicator and MSSD test.
Author: Donna S. Harmelink
Publisher:
ISBN:
Category : Asphalt emulsion mixtures
Languages : en
Pages : 110
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Book Description
Documents the construction and performance of the research study which was initiated to address section 1038(d) of the 1991 Intermodal Surface Transportation Efficiency Act (ISTEA). The project selected to demonstrate the crumb rubber process was located on Platt Canyon (SH 75) from Bowles to C470 in the Denver metropolitan area. The project was a low volume roadway and quantities of crumb rubber introduced into the mix were minimal. This was to reduce risk in terms of premature failure and Colorado's limited experience with crumb rubber. Because of this limited experience, the "dry" process was selected. The project contained four different mix designs. A mix containing 1% [20 lb/ton (10 kg/Mg)] crumb rubber, a mix containing 1 lb/ton (0.5 kg/Mg), a mix containing 3 lb/ton (1.5 kg/Mg) and a mix which contained no rubber were placed on the project.
