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Open Access Publications from the University of California

Scholarly Works (31 results)

  • Article
Research Reports (2008)
CalME is a software package under development for Caltrans that is intended to help in the evaluation and design of flexible pavement structures. Building on existing design methods, CalME provides an Incremental-Recursive Mechanistic-Empirical (IRME) method in which the materials properties for the pavement are updated in terms of damage as the simulation of the pavement life progresses. The IRME design method incorporates various mathematical models to describe material behaviors and predict structure performances. These models need to be calibrated before they can be used to evaluate performance of different flexible pavement structures. This technical memorandum focuses on calibration of the incremental-recursive rutting model used in CalME when employing data collected during the APT (accelerated pavement testing) conducted in the first research cycle (years 2000–2002) at the NCAT (National Center for Asphalt Technology) pavement test track. It was found that the shift factor in CalME calibrated by rutting data in Heavy Vehicle Simulator tests led to a satisfactory match between calculated and measured rutting performance of the selected NCAT test sections.
    Cover page: Calibration of the CalME Rutting Model Using 2000 NCAT Data
    • Article
    Research Reports (2011)
    A relatively unique opportunity was recently identified for accelerated traffic load testing of a new bridge expansion joint design. This study was part of the construction of the new East Span of the San Francisco–Oakland Bay Bridge and assessed whether these new Caltrans seismic expansion joints (which were designed to function in harmony with the bridge decks in the event of a high-magnitude earthquake) linking the Self-anchored Span with the Transition and Skyway spans would withstand truck traffic loading. A test structure incorporating one of the full-scale joints was constructed close to the actual bridge and tested with the California Department of Transportation / University of California Pavement Research Center Heavy Vehicle Simulator in a series of phases. A total of 1.36 million load repetitions, equating to about 46 million equivalent standard axle loads, were applied in seven phases during the three-month test. On completion of this testing, no structural damage was recorded by any of the Linear Variable Differential Transducers or strain gauges installed on the steel plates, steel frames, bolts, or washers. There was also no visible damage on any of these components. Excessive overloading with a 150 kN halfaxle load in the last phase of the test caused some damage to the Trelleborg unit of the joint. This included abrasion, tearing, shoving and permanent deformation of the rubber inserts, and deformation and shearing of one of the steel supports directly under the wheel load. Based on the results of this limited testing, it was concluded that the Caltrans seismic expansion joint would perform adequately under typical Bay Bridge traffic. The distress observed to the Trelleborg unit under the high loads in the last phase of testing is unlikely to occur under normal traffic. However, the Trelleborg unit was found to be the weakest point of the expansion joint, as expected. On the actual bridge structure, these units will require periodic maintenance and replacement in line with manufacturer’s specifications. The findings from this study indicate that the Caltrans seismic expansion joint tested would be appropriate for typical Bay Bridge traffic. No seismic or structural testing was undertaken on the seismic expansion joint as part of this study and no recommendations toward its seismic or structural performance are made. Ride quality, skid resistance, and tire noise studies were carried out by Caltrans in a separate study and are reported on in separate Caltrans reports.
      Cover page: Accelerated Traffic Load Testing of Expansion Joints for the Self-anchored Suspension Section of the New San Francisco–Oakland Bay Bridge East Span
      • Article
      • Peer Reviewed
      Recent Work (2008)

      This report is the fourth in a series of first-level analysis reports that describe the results of HVS testing on a fullscale experiment being performed at the Richmond Field Station (RFS) to validate Caltrans overlay strategies for the rehabilitation of cracked asphalt concrete. It describes the results of the fourth HVS reflective cracking testing section, designated 588RF, carried out on a 90 mm full-thickness AR4000-D overlay, which was included as a control for performance comparison purposes. The test forms part of Partnered Pavement Research Center Strategic Plan Item 4.10: “Development of Improved Rehabilitation Designs for Reflective Cracking”. HVS trafficking on the section commenced on November 2, 2005 and was completed on April 11, 2006. A total of 1,410,000 load repetitions, equating to 37 million ESALs and a Traffic Index of 13.8, was applied during this period. A temperature chamber was used to maintain the pavement temperature at 20°C±4°C for the first one million repetitions, then at 15°C±4°C for the remainder of the test. A dual tire (720 kPa pressure) and bidirectional loading with lateral wander configuration was used. Findings and observations based on the data collected during this HVS study include:

      • On completion of testing, the surface crack density was 9.1 m/m2 and was mostly confined to one half of the section. Alligator cracking predominated on the overlay, similar to that on the underlying layer. The crack patterns of the two layers did not match exactly; however, the areas of most severe cracking corresponded.

      • The average maximum rut depth across the entire test section at the end of the test was 15.9 mm. The rate of rutting was relatively slow during the early part of the experiment, but increased significantly after the 100 kN load change, despite reducing the pavement temperature to 15°C±4°C.

      • Ratios of final-to-initial surface elastic deflections show that damage had increased significantly in the pavement structure by the end of trafficking, with loss of stiffness highest in the area of most severe cracking in the underlying layer.

      • Analysis of surface profile measurements indicate that most of the permanent deformation probably occurred in the asphalt-bound surfacing layers (overlay and cracked DGAC) with the highest damage occurring in the area of most severe cracking in the underlying DGAC layer. No in-depth elastic deflection or permanent deformation data were collected due to problems with the MDDs. Malfunction was attributed to the loss of anchorage of the modules resulting from very wet conditions in the lower layers of the pavement and subgrade.

      • Parts of the test were carried out during relatively high rainfall. This resulted in ponding of water adjacent to the section. Some pumping of fines through the cracks was noted in the final days of testing. No recommendations as to the use of the modified binders in overlay mixes are made at this time. These recommendations will be included in the second-level analysis report, which will be prepared and submitted on completion of all HVS and laboratory testing.

        Cover page: Reflective Cracking Study: First-level Report on HVS Testing on Section 588RF - 90 mm AR4000-DOverlay
        • Article
        • Peer Reviewed
        Recent Work (2008)

        This report is the third in a series of first-level analysis reports that describe the results of HVS testing on a full-scale experiment being performed at the Richmond Field Station (RFS) to validate Caltrans overlay strategies for the rehabilitation of cracked asphalt concrete. It describes the results of the third HVS reflective cracking testing section, designated 587RF, carried out on a 45 mm half-thickness RAC-G overlay, which was included as a control for performance comparison purposes. The test forms part of Partnered Pavement Research Center Strategic Plan Item 4.10: “Development of Improved Rehabilitation Designs for Reflective Cracking”. HVS trafficking on the section commenced on March 15, 2005 and was completed on October 10, 2005. A total of 2,024,793 load repetitions, equating to 66 million ESALs and a Traffic Index of 15, was applied during this period. A temperature chamber was used to maintain the pavement temperature at 20°C±4°C for the first one million repetitions, then at 15°C±4°C for the remainder of the test. A dual tire (720 kPa pressure) and bidirectional loading with lateral wander configuration was used. Findings and observations based on the data collected during this HVS study include:

        • On completion of testing, the surface crack density was 3.6 m/m2. Cracking on the overlay was predominantly transverse, as was that on the underlying layer. The crack patterns of the two layers did not match exactly; however, the areas of most severe cracking corresponded.

        • The average maximum rut depth across the entire test section at the end of the test was 18.2 mm. The rate of rutting was relatively slow during the early part of the experiment, but increased significantly after the 100 kN load change, despite reducing the pavement temperature to 15°C±4°C.

        • Both of the failure criterion set for the experiment were reached within 100,000 load repetitions of each other.

        • Ratios of final-to-initial elastic deflections show that damage had increased significantly at all depths in the pavement structure by the end of trafficking, with loss of stiffness highest in the area of most severe cracking in the underlying layer.

        • Analysis of surface profile and in-depth permanent deformation measurements indicate that most of the permanent deformation occurred in the asphalt-bound surfacing layers (overlay and cracked DGAC) with approximately twice as much damage occurring in the area of most severe cracking in the underlying DGAC layer. Permanent deformation was also recorded in the upper part of the aggregate base in this area. Negligible deformation was recorded in the subgrade. No recommendations as to the use of the modified binders in overlay mixes are made at this time.

        These recommendations will be included in the second-level analysis report, which will be prepared and submitted on completion of all HVS and laboratory testing.

          Cover page: Reflective Cracking Study: First-level Report on HVS Testing on Section 587RF - 45 mm RAC-G Overlay
          • Article
          • Peer Reviewed
          Recent Work (2008)

          This report is the sixth in a series of first-level analysis reports that describe the results of HVS testing on a fullscale experiment being performed at the Richmond Field Station (RFS) to validate Caltrans overlay strategies for the rehabilitation of cracked asphalt concrete. It describes the results of the sixth HVS reflective cracking testing section, designated 591RF, carried out on a 45-mm half-thickness MAC15TR gap-graded overlay with 15 percent recycled tire rubber. The test forms part of Partnered Pavement Research Center Strategic Plan Element 4.10: “Development of Improved Rehabilitation Designs for Reflective Cracking.” HVS trafficking on the section commenced on January 10, 2007, and was completed on June 25, 2007. A total of 2,554,335 load repetitions, equating to 90.8 million ESALs and a Traffic Index of 15.4, was applied during this period. Temperatures were maintained at 20°C±4°C for the first one million repetitions, then at 15°C±4°C for the remainder of the test. Caltrans and the UCPRC jointly agreed to halt HVS trafficking at this point as there was no indication of the failure criteria being reached in the near future. Findings and observations based on the data collected during this HVS study include:

          • No cracking was observed on the section. This implies that the MAC15TR overlay successfully prevented reflective cracking.

          • The average deformation and average maximum rut depth across the entire test section was just 1.7 mm and 4.6 mm, respectively, considerably lower than the failure criterion of 12.5 mm. The maximum rut depth measured was 8.2 mm. The MAC15TR overlay thus did not appear susceptible to rutting at the temperature range under which the test was conducted.

          • Ratios of final-to-initial elastic surface deflections under a 60 kN wheel load increased by between 3.7 and 4.0 times along the length of the section. The ratios for in-depth deflections show that damage increased at all depths in the pavement structure by the end of trafficking. Loss of stiffness was highest in the area of most severe cracking in the underlying DGAC layer.

          • Analysis of surface profile and in-depth permanent deformation measurements indicates that most of the permanent deformation (55 and 60 percent) occurred in the asphalt-bound surfacing layers (overlay and cracked DGAC) with the remainder mostly in the aggregate base layer. No recommendations as to the use of the modified binders in overlay mixes are made at this time. These recommendations will be included in the second-level analysis report, which will be prepared and submitted on completion of all HVS and laboratory testing.

            Cover page: Reflective Cracking Study: First-level Report on HVS Testing on Section 591RF - 45 mm MAC15TR-GOverlay
            • Article
            Research Reports (2016)
            This first-level report describes the first two phases of a study comparing the performance of four different full-depth pavement reclamation strategies, namely pulverization with no stabilization (FDR-NS), stabilization with foamed asphalt and portland cement (FDR-FA), stabilization with portland cement only (FDR-PC), and stabilization with engineered asphalt emulsion (FDR-EE). A literature review, the test track layout and design, stabilization and asphalt concrete mix designs, and test track construction are discussed, as well as the results of Heavy Vehicle Simulator (HVS) and preliminary laboratory testing, and a forensic investigation of the HVS test sections. A number of problems were experienced during construction of the FDR-PC and FDR-EE lanes on the test track and consequently only the FDR-NS and FDR-FA lanes and one section of the FDR-PC lane (5 percent measured cement content) were considered satisfactorily uniform for the purposes of HVS testing. The FDR-FA and FDR-PC sections performed very well under both dry and wet conditions, with testing under dry conditions terminated long before the terminal rut of 0.5 in. (12.5 mm) or average crack density of 0.75 ft/ft2 (2.5 m/m2 ) were reached (cracks were observed on the wet tests only). The two FDR-NS sections tested performed acceptably, with a section with thicker asphalt surfacing (0.4 ft [120 mm]) outperforming a section with thinner asphalt surfacing (0.2 ft [60 mm]) under both dry and wet conditions, as expected. Terminal rut was reached on both sections. No cracks were observed during dry tests, but cracking was severe after completion of the wet tests. Observations during a forensic investigation confirmed the measurements taken during HVS testing. The performance advantages of full-depth reclamation strategies that either use foamed asphalt with cement or cement only over those with no stabilization are clearly evident from the results. Additional laboratory and field testing is in progress to collect sufficient data for the development of mechanisticempirical design criteria (and revised gravel factors) for full-depth reclaimed pavements. However, there is sufficient evidence to show that pavements that are rehabilitated using full-depth reclamation strategies will satisfactorily withstand design traffic levels common in California. Rehabilitation using this approach offers additional advantages of speed of construction, minimal disruption to traffic, reuse of all materials, and does not require removal of material from the site. FDR with these stabilization approaches also effectively replaces extensively cracked existing asphalt layers, providing a new base and thus preventing the reflective cracking that is common in more traditional overlay projects. Future research should include life cycle cost analysis (LCCA) and environmental life cycle assessment (LCA) to compare FDR with overlay strategies for the range of pavement, climate and traffic conditions where the two strategies might be used. Future research on partial- and full-depth reclamation should be coordinated to facilitate consistent design and specification documentation, and to facilitate the preparation of a comprehensive guide covering all forms of pavement recycling.
              Cover page: Full-Depth Recycling Study: Test Track Construction and First-Level Analysis of Phase 1 and Phase 2 HVS Testing, Forensic Investigation, and Phase 1 Laboratory Testing
              • Article
              Research Reports (2014)
              This first-level report describes the first phase of a study comparing the performance of four different full-depth pavement reclamation strategies, namely pulverization with no stabilization (FDR-NS), stabilization with foamed asphalt and portland cement (FDR-FA), stabilization with portland cement only (FDR-PC), and stabilization with engineered asphalt emulsion (FDR-EE). A literature review, the test track layout and design, stabilization and asphalt concrete mix designs, and test track construction are discussed, as well as results of Heavy Vehicle Simulator (HVS) and laboratory testing. A number of problems were experienced during construction of the FDR-PC and FDR-EE lanes on the test track and consequently only the FDR-NS and FDR-FA lanes and one section of the FDR-PC lane (5 percent measured cement content) were considered satisfactorily uniform for the purposes of accelerated pavement testing. The FDR-FA and FDR-PC sections performed very well and testing on both was terminated long before the terminal rut of 0.5 in. (12.5 mm) or average crack density of 0.8 ft/ft2 (2.5 m/m2 ) were reached (no cracks were observed on either section). The two FDR-NS sections performed acceptably, with the section with the thicker asphalt surfacing (120 mm) outperforming the section with the thinner asphalt surfacing (60 mm), as expected. Terminal rut was reached on both sections, but no cracking was observed. The FDR-EE sections performed poorly, with terminal rut and terminal cracking both reached after a limited number of load repetitions. This poor performance was attributed to problems associated with construction, and consequently no conclusions can be drawn from the test results regarding this stabilization strategy. The advantages of using foamed asphalt with cement and cement only recycling strategies over recycling strategies with no stabilization are clearly evident from the results. A second phase of accelerated pavement testing, full-scale field testing, and additional laboratory testing are planned to collect sufficient data for the development of mechanistic-empirical design criteria (and revised gravel factors) for full-depth reclaimed pavements. However, there is sufficient evidence to show that pavements that are rehabilitated using full-depth reclamation strategies will satisfactorily withstand design traffic levels common in California. Rehabilitation using this approach is quick, has minimal disruption to traffic, reuses all materials, does not require removal of material from the site, and effectively replaces weak base layers, thus preventing reflective cracking that is common in more traditional overlay projects. Based on these conclusions, it is recommended that full-depth reclamation be promoted as an appropriate rehabilitation strategy in California. Future research on partial- and full-depth reclamation should be coordinated to facilitate consistent design and specification documentation, and to facilitate the preparation of a comprehensive guide covering all forms of pavement recycling.
                Cover page: Full-Depth Recycling Study: Test Track Construction and First Level Analysis of Phase 1 HVS and Laboratory Testing
                • Article
                • Peer Reviewed
                Recent Work (2008)

                This report is the fifth in a series of first-level analysis reports that describe the results of HVS testing on a full-scale experiment being performed at the Richmond Field Station (RFS) to validate Caltrans overlay strategies for the rehabilitation of cracked asphalt concrete. It describes the results of the fifth HVS reflective cracking testing section, designated 586RF, carried out on a 45-mm half-thickness MB4 gap-graded overlay with 15 percent recycled tire rubber. The test forms part of Partnered Pavement Research Center Strategic Plan Element 4.10: “Development of Improved Rehabilitation Designs for Reflective Cracking.”

                HVS trafficking on the section commenced on May 25, 2006, and was completed on November 21, 2006. A total of 2,492,387 load repetitions, equating to 87.9 million ESALs and a Traffic Index of 15.3, was applied during this period. Temperatures were maintained at 20°C±4°C for the first one million repetitions, then at 15°C±4°C for the remainder of the test. Caltrans and the UCPRC jointly agreed to halt HVS trafficking at this point as there was no indication of the failure criteria being reached in the near future.

                Findings and observations based on the data collected during this HVS study include:

                • No cracking was observed on the section. This implies that the MB15-G overlay successfully prevented reflective cracking.

                • The average maximum rut depth across the entire test section was just 4.6 mm, considerably lower than the failure criterion of 12.5 mm. The maximum rut depth measured was 7.7 mm. The MB15-G overlay thus did not appear susceptible to rutting at the temperature range under which the test was conducted.

                • Ratios of final-to-initial elastic surface deflections under a 60 kN wheel load increased by between 1.4 and 1.9 times along the length of the section. The ratios for in-depth deflections show that damage increased at all depths in the pavement structure by the end of trafficking. Loss of stiffness was highest in the area of most severe cracking in the underlying DGAC layer.

                • Analysis of surface profile and in-depth permanent deformation measurements indicates that most of the permanent deformation (approximately 55 percent) occurred in the asphalt-bound surfacing layers (overlay and cracked DGAC) with the remainder mostly in the aggregate base layer.

                No recommendations as to the use of the modified binders in overlay mixes are made at this time. These recommendations will be included in the second-level analysis report, which will be prepared and submitted on completion of all HVS and laboratory testing.

                  Cover page: Reflective Cracking Study: First-level Report on HVS Testing on Section 586RF - 45 mm MB15-GOverlay
                  • Article
                  Research Reports (2007)
                  UCPRC staff attended the 2006 RPA conference in Palm Springs, CA. This document contains brief summaries of the technical papers/presentations given in both the technical and practical portions of the event. Items within specific papers that may be implementable by Caltrans are noted. Suggestions for future research, development, and information dissemination are given.
                    Cover page: Summary and Recommendations toward Implementing Innovations Based on Selected Presentations at the Asphalt Rubber Pavement Conference (AR2006), October 2006
                    • Article
                    Research Reports (2017)
                    Fully permeable pavements capture stormwater and infiltrate it into the ground and/or hold it until discharging it into stormwater conveyance. In either case, they offer benefits in terms of reducing or eliminating the need for stormwater conveyance infrastructure, capturing pollutants, and potentially reducing air temperatures around them. This technical memorandum reviews recent advances in structural design, materials, and hydraulic design that have filled many of the gaps in permeable pavement technology. The memo then presents the results of a recent survey in California, with some additional out-of-state responders, regarding awareness of permeable pavements and obstacles to their implementation. Finally, the memo presents recommendations for filling remaining knowledge gaps and overcoming obstacles to implementation.
                      Cover page: Fully Permeable Pavement for Stormwater Management: Progress and Obstacles to Implementation in California
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