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NEWS (Previous News Items)

  • The work being done by the UCPRC for Caltrans and others was presented at the Australian Asphalt Pavement Association Annual Conference from September 14-16, 2015. Presentations were made on CalME mechanistic-empricial design, development of mechanistic-empirical design methods, heavy duty asphalt pavement design, and a keynote address on driving innovation in pavements. Posted 10/19/2015.
  • A summary of the research findings and design procedure developed during the recently completed permeable interlocking concrete pavement study (see Summer 2015 UCPRC Activities below) was presented at the 11th International Conference on Concrete Block Pavement in Dresden, Germany in September. The design tables developed with the design procedure have been incorporated into the Interlocking Concrete Pavement Institute and ASTM guidelines for designing and constructing permeable interlocking concrete pavements. Posted 10/13/2015.
  • The Caltrans/UCPRC Heavy Vehicle Simulators have completed all testing of different full-depth pavement reclamation strategies on one of the instrumented test tracks at the UC Davis research facility. The strategies included pulverization with no stabilizer (FDR-NS), pulverization with cement (FDR-PC), pulverization with foamed asphalt/cement (FDR-FA), and pulverization with engineered emulsion (FDR-EE). Testing was done under both dry and soaked conditions, with a total of 8.5 million wheel load repetitions applied with the HVSs, equating to about 145 million equivalent single axle loads (ESALs) . A comprehensive forensic investigation has also been completed on each test section. Posted 10/13/2015.
  • The UCPRC has recently worked with colleagues in China and South Africa to expand knowledge of pavement life cycle assessment and support development of national programs for considering development and implementation of pavement LCA. A two day workshop (August 7-8) organized by Jia Yu of the Jiangsu Transportation Institute Group Company, Ltd. and Tan Yiqiu of the Harbin Institute of Technology, who also hosted the event, drew participants from across a wide range of stakeholders in China. Keynote presentations given by UCPRC are available here. In South Africa, the UCPRC participated in the 3rd ISAP International Symposium on Asphalt Pavements and the Environment which focused on improving the sustainability of pavements and was part of the 11th Conference on Asphalt Pavements in Southern Africa. The keynote presentation given by UCPRC on pavement LCA is available here. A workshop was held with industry, government and academic participants to discuss pavement LCA for application in southern Africa, and a resolution has been prepared from the workshop for review by government and industry in South Africa. Posted 8/25/2015.
  • A presentation by UCPRC researchers at the 52nd Petersen Asphalt Research Conference (July 13 to 15, 2015, in Laramie, Wyoming) described the progress of, and some recent findings from, three current studies: 1) Modification of the rolling thin-film oven (RTFO) test to simulate the realistic short-term aging of asphalt rubber binders (view presentation); 2) An evaluation of changes in the performance-related properties of conventional asphalt binder after it is blended with different amounts of age-hardened rubberized binder (view presentation); and 3) Development of a solvent-free approach for evaluating the properties of blended binders in mixes that have large reclaimed asphalt pavement (RAP) and reclaimed asphalt shingle (RAS) content (view presentation). Posted 8/7/2015.
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Summer 2015 UCPRC Activities


Candidate for fully permeable shoulder retrofit validation site

Permeable Interlocking Concrete Pavement Study. The UCPRC recently completed a study on behalf of the Interlocking Concrete Pavement Institute (ICPI) and the Concrete Masonry Association of California and Nevada to develop revised design tables for permeable interlocking concrete pavement using a mechanistic-empirical design approach. The study included a literature review, field testing of existing projects and test sections, estimation of the effective stiffness of each layer in permeable interlocking concrete pavement structures, mechanistic analysis and structural design of a test track incorporating three different subbase thicknesses (low, medium, and higher risk), tests on the track with a Heavy Vehicle Simulator to collect performance data to validate the design approach using accelerated loading, refinement and calibration of the design procedure using the test track data, development of a spreadsheet based design tool, and development of revised design tables using the design tool.

Key findings from the mechanistic analysis include:

  • Higher shear stress/strength ratios at the top of the subgrade, which equate to a higher risk of rutting in the subgrade, require thicker subbase layers, as expected.
  • An increase in the stiffness of the surface layer reduces the required subbase layer thickness to achieve the shear stress/strength ratio. However, the effect of the surface layer stiffness on overall pavement performance is not significant due to the relatively low thickness of the pavers (80 mm) and the reduced interlock between them compared to pavers with sand joints.
  • For the same shear stress/strength ratio at the top of the subbase, an increase in the stiffness of the subbase layer reduces the required thickness of that subbase layer, especially when the subgrade has a low stiffness.
  • For the same shear stress/strength ratio at the top of the subgrade, wet conditions require thicker subbase layers compared to the dry condition, confirming that wet conditions are the most critical condition for design.

A new example design table, based on the number of days with standing water in the subbase (zero, 10, 30, 50, 90, and 120) has been developed. The table uses a similar format to that currently used in the ICPI Permeable Interlocking Concrete Pavements guideline. The minimum design thicknesses required to prevent subgrade rutting that are proposed in the new table do not differ significantly from those in the current ICPI guide, and are mostly less conservative. Designs for a specific set of project circumstances can be undertaken using the same Excel® spreadsheet-based design tool used to develop the tables in conjunction with the hydrological design procedures provided in the ICPI guide.

Important Note for Caltrans Users: Prior to scheduling pavement preservation (preventive maintenance or CAPM) or roadway rehabilitation work on flexible pavement highway sections, the District Materials Engineer and/or the Project Manager should review this spreadsheet to ensure that the proposed project does not include sections active in the “Quieter Pavement Research” (QPR) testing program. If the proposed project is within a QPR test section, please contact Linus Motumah of the Caltrans Office of Pavement Design before scheduling the work.

To view maps that show where the sections are located, click the following link: (or copy-and-paste it into a new browser window for a slightly larger view).

For more information, contact John Harvey of the UCPRC or Linus Motumah.