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NEWS (Previous News Items)

  • Upcoming Symposium, January 13-15, 2021: International Symposium on Pavement, Roadway, and Bridge Life Cycle Assessment 2020. Due to the current pandemic COVID-19, the International Symposium on Pavement, Roadway, and Bridge Life Cycle Assessment 2020, has been rescheduled to January 13-15, 2021, and will now be held in Davis, CA. The symposium will cover such areas as recent advances in quantifying environmental impacts using LCA for pavement, roadways, and bridges; current status and future developments; and standardization and implementation of pavement, roadway, and bridge LCA. Registration is Now OPEN.
    Posted 12/13/2019; Updated 4/24/2020.
  • New Research Report Published: Development of Improved Guidelines and Designs for Thin Whitetopping: Environmental Response of Full-Scale BCOA Sections. “Fifteen bonded concrete overlay of asphalt (BCOA) sections were built at the UCPRC facility in Davis, California, from February 23 to 25, 2016. The concrete mixes included Type II/V and Type III portland cements and calcium sulfoaluminate cement, and they were designed to provide 2.8 MPa (400 psi) flexural strength after either 4 or 10 hours. Six of the 15 sections were instrumented with a total of 245 sensors to measure the responses to environmental actions and cement hydration. Based on the analysis of the data collected by these sensors up until May 31, 2017, preliminary conclusions were drawn regarding how the different section configurations and concrete types responded to moisture and temperature-related actions. A clear link between drying shrinkage, concrete relative humidity, and environmental conditions was verified. Very high levels of drying shrinkage were measured...”
    Posted 5/18/2020.
  • New Tech Memo Published: Development of Thin Bonded Concrete Overlay of Asphalt Design Method: Evaluation of Existing Mechanistic-Empirical Design Methods. “The California Department of Transportation (Caltrans) is interested in advancing the technology needed to implement thin bonded concrete overlay of asphalt (BCOA) on its road network. Recent accelerated pavement tests showed that thin BCOA exhibited promising results for structural performance and constructability in California’s dry environment when made with the high early-strength concrete mixes typically used by Caltrans. However, to continue moving forward, Caltrans needs to adopt a thin BCOA design method since the current Caltrans Highway Design Manual does not consider this type of pavement. In order to help Caltrans decide how to adopt a thin...”
    Posted 4/24/2020.
  • Presentation: Alameda County Green Procurement Roundtable-December 10, 2019. John Harvey made a presentation to the Alameda County Green Procurement Roundtable in Hayward on 10 December, 2019 to an audience of city and county pavement engineers, sustainability officers, and procurement officers. The presentation covered methods to quantify environmental impacts, and recommendations for how local government can reduce the impacts of their pavement operations and decisions.
    Posted 12/13/2019.
  • New Research Report Published: Development of Improved Guidelines and Designs for Thin BCOA: Summary, Conclusions, and Recommendations. This report summarizes the investigations undertaken by the UCPRC between 2014 and 2017 to develop recommendations and guidance on the use of thin bonded concrete overlay of asphalt (BCOA) as a rehabilitation alternative for California based on the adoption of, and improvements to, the technology developed in other US states. The report summarizes, among other things, the Heavy Vehicle Simulator testing of eleven thin BCOA sections. The main conclusion from this research project is that a well-designed, well-built 6×6 thin bonded concrete overlay placed on top of an asphalt base that is in fair-to-good condition can potentially provide 20 years of good serviceability on most of California’s non-interstate roadways.
    Posted 8/19/2019.
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Winter 2020 UCPRC Activities

Candidate for fully permeable shoulder retrofit validation site

UCPRC conducts research on partial- and full-depth recycling, RHMA-G strategies, with a big assist from CalAPA members. This past May, the UCPRC—with major assistance from members of the California Asphalt Pavement Association (CalAPA)—continued with the next phases of two comprehensive research studies into the use of recycled materials in pavements being conducted for the California Department of Transportation (Caltrans). The work covered the construction of a four-lane test track with 10 different sections. Two lanes are dedicated to investigating cold central plant recycled materials and two lanes focus on rubberized asphalt concrete. The sections will be subjected to accelerated pavement testing in conjunction with laboratory testing with the aim of increasing the use of recycled/reclaimed materials, improving pavement life, and reducing costs.

The test sections are currently being tested to answer two sets of questions:

  • How do Cold Central Plant Recycled (CCPR) materials prepared with different methods stabilizers perform mechanistically?
    • These test results will be compared with results from earlier testing of different full-depth reclamation (FDR) stabilization approaches and with data from field performance monitoring of projects rehabilitated using cold in-place recycling strategies.
  • What are the effects of different thicknesses and nominal maximum aggregate sizes on the rutting performance of gap-graded rubberized hot mix asphalt (RHMA-G)?

CCPR practice processes 100 percent reclaimed asphalt pavement (RAP) stabilized with either foamed asphalt or asphalt emulsion and an active filler in a mobile plant at or close to the construction project. The processed material is placed with a paver and then compacted before it is surfaced with a thin layer of asphalt concrete. The accelerated pavement testing will provide information about this material’s long-term mechanistic behavior under traffic loading and different environmental conditions.

The RHMA-G experiment includes thicker layers of the material than are typically used—which can potentially result in more scrap tires being recycled into pavement—to evaluate their rutting performance under heavy loads and high temperatures. In addition, the thicker layers will also provide a look at the effects that different aggregate sizes in the RHMA-G have on rutting performance, and address Industry’s interest in using smaller maximum aggregate sizes to facilitate construction compaction and to meet smoothness requirements. A third aspect of this testing focuses on the use of small amounts of RAP in RHMA-G, primarily to replace aggregate to help reduce the RHMA-G cost without reducing the number of tires included in the mixes.

The findings of both studies will be used to refine pavement design, mix design, specification language, and performance expectations for these materials, and to provide confidence to highway engineers who design rehabilitation projects. The accelerated pavement testing results are also used with extensive laboratory testing to improve models for future pavement rehabilitation designs.

The UCPRC acknowledges the interest and support of the following organizations who assisted with the construction of the test track. Pavement Recycling Systems provided materials and equipment, processed all CCPR materials, and did the paving and compaction. They also placed and compacted the RHMA-G surface layers. Pacific Northwest Oil, Albina Asphalt, and Ergon Asphalt and Emulsions provided the binders for the CCPR materials. Asphalt Pavement and Recycling Technologies (APART) did the CCPR mix designs. George Reed did the RHMA-G mix designs and provided all the RHMA-G mixes. Aragon Geotechechnical, Graniterock, Surface Systems and Instruments, and Humboldt manufacturing assisted with quality control during construction.