Dedicated to providing knowledge, the Pavement Research Center uses innovative
research and sound engineering
principles to improve pavement structures, materials, and technologies.

NEWS (Previous News Items)

  • Call for Abstracts: The International Symposium on Pavement, Roadway, and Bridge Life Cycle Assessment 2020, to be held in Sacramento, California on June 3-6, 2020 is now accepting abstracts. Abstracts should be submitted by June 15, 2019. To submit abstracts, you need to set up an account with EasyChair. Go to https://easychair.org/conferences/?conf=lca2020 and click “create an account”. The LCA2020 Instructions for Authors document details the process of creating an EasyChair account and submitting an abstract. You only need to specify the first author at submission time (you can specify all authors if you would like) andyou can add additional authors (or remove and/or update authors) later by logging into EasyChair andupdating your submission.
    Posted 3/12/2019.
  • New Research Report Published: Pavement Recycling: Shrinkage Crack Mitigation in Cement-Treated Pavement Layers - Phase 1 Laboratory Testing. “The California Department of Transportation (Caltrans) has been using full-depth reclamation (FDR) as a rehabilitation strategy since 2001. Most projects to date have used a combination of foamed asphalt and portland cement as the stabilizing agent. Recently though, the fluctuating and at times high cost of asphalt binder coupled with the relatively complex mix-design procedure for mixes that include foamed asphalt has generated interest in the use of portland cement alone as an alternative stabilizing agent. However, shrinkage cracking associated with the hydration and curing...”
    Posted 12/10/2018.
  • New Research Report Published: Guidance for Selection of Unbound Pavement Layer Seasonal Stiffnesses. “One of the benefits of using mechanistic-empirical (ME) design methods for pavements is the ability to calculate pavement response to various loading and climate conditions, and then in turn to model the entire damage process that is expected to occur over the pavement lifetime. One property that is currently not accounted for within California’s ME design software (CalME) is the change in stiffness of unbound materials that may occur due to seasonal moisture patterns. The engineering properties of unbound material may change due to a variety of factors, such as fluctuations in water content, changes in suction during wetting or drying periods, changes in overburden stress, and they are also dependent on geologic setting. Before moving to develop and implement more complex relationships to model assumed changes in the properties of unbound layers due to seasonal moisture changes...”
    Posted 11/20/2018.
  • New Research Report Published: Mechanistic-Empirical (ME) Design: Mix Design Guidance for Use with Asphalt Concrete Performance-Related Specifications. “Caltrans has adopted mechanistic-empirical (ME) methods for flexible pavement design, and is using performance-related construction specifications on some projects for hot mix asphalt. Performance-related specifications are used to help ensure that as-built materials meet the performance requirements assumed in ME pavement structural designs. PRS pose new challenges for materials producers and contractors who have never had to relate volumetric mix design parameters to achievement of mechanistic parameters for fatigue life and rutting resistance based on results from performance-related laboratory tests. The objective of this project is to provide guidance to mix designers and contractors to support their decision making regarding changes to mix designs to achieve PRS requirements. The guidance presented in this report was initially developed based on past experience. To validate...”
    Posted 8/24/2018.
  • New Research Report Published: Development of Improved Guidelines and Designs for Thin Whitetopping: Design, Instrumentation, Construction and Initial Environmental Response of Full-Scale BCOA Sections. “Thin bonded concrete overlay of asphalt (BCOA) is a rehabilitation alternative consisting of a 100 to 175 mm (0.33 to 0.58 ft) thick portland cement concrete (PCC) overlay of an existing flexible or composite pavement. Fifteen BCOA sections were built at the Davis facilities of the University of California Pavement Research Center in February 2016. Eleven of these full-scale sections were tested under accelerated loading, while four of them were used for monitoring the response of BCOA to the ambient environment and cement hydration. This full-scale experiment is part of a research project whose primary goal is to develop recommendations and guidance on the use of thin BCOA as a rehabilitation alternative in California. The design and construction of these sections is presented in this report, together with results from the quality control/quality assurance testing that was conducted. This testing...”
    Posted 8/20/2018.
  • New Research Report Published: Final Report: Permeable Pavement Road Map Workshop and Proposed Road Map for Permeable Pavement. “In early 2017, the University of California Pavement Research Center (UCPRC) and the National Center for Sustainable Transportation (NCST), working with the Interlocking Concrete Pavement Institute (ICPI), identified gaps in knowledge and other barriers to wider implementation that were perceived to be holding back the full potential for deployment of pavements that can simultaneously solve transportation, stormwater quality, and flood control problems. Further discussions were held with the National Ready Mixed Concrete Association (NRMCA), the National Asphalt Pavement Association (NAPA), and the Tongji University Sponge City Project (Shanghai, China). A workshop was organized in November 2017 based on those discussions with the goal of identifying...”
    Posted 8/16/2018.
  • New Tech Memo Published: Effects of Milling and Other Repairs on Smoothness of Overlays: Additional Testing on Construction Under Profiler-Based Smoothness Specifications. “This technical memorandum provides additional information regarding smoothness on several thin asphalt overlay projects constructed soon after changes in Caltrans specifications for constructed pavement surfaces using the International Roughness Index (IRI) as the quality metric. The IRI data were collecting using inertial profilers, before and after construction, on overlaid surfaces employing one of three repairs—digouts, cold in-place recycling (CIR), mill and filling—or none. Because the data were collected after the close of the construction contract, they include the effects of any grinding that Caltrans...”
    Posted 7/17/2018.
  • Two Presentations Given: A presentation on Reducing Pavement Life Cycle Impacts Using LCA was made by UCPRC at the California Asphalt Pavement Association (CalAPA) Conference and Equipment Expo on April 25, 2018. A keynote presentation on Asphalt Pavement Life Cycle Assessment: Review and Future Outlook was given by John Harvey in Harbin, China for the International Symposium on Road Development on May 5, 2018.
    Posted 6/15/2018.
  • New Tech Memo Published: Development of the CalME Standard Materials Library. “The main purpose of the project is to improve the ability of Caltrans pavement designers to use mechanistic-empirical (ME) pavement design procedures that were developed and calibrated for California conditions as part of Partnered Pavement Research Center Strategic Plan Element (PPRC SPE) 4.1 and refined in SPE 3.4. Specifically this project is part of a long-term series of tasks to collect regional materials data for use by Caltrans in ME flexible pavement designs and rehabilitations. This technical memorandum documents ...”
    Posted 4/19/2018.
  • New Tech Memo Published: Permeability Testing on Dense-Graded Hot Mix Asphalt (HMA) and Gap-Graded Rubberized Hot Mix Asphalt (RHMA-G) Surfaces. “Falling head permeability tests were conducted on seven projects, four with dense-graded hot mix asphalt surfaces and three with gap-graded rubberized hot mix asphalt surfaces. Tests were conducted between the two wheelpaths and in the right wheelpath, and in both directions of traffic. Averaging all the test results shows that ...”
    Posted 3/26/2018.
  • New Guideline Published: Guidelines for the Selection, Specification and Application of Chemical Dust Control and Stabilization Treatments on Unpaved Roads. This guide introduces a new process for selecting an appropriate chemical treatment category for a specific set of unpaved road conditions using ranked potential performance. The process is based on a practitioner’s setting an objective for initiating a chemical treatment program and then gaining a fuller understanding of the road in terms of materials, traffic, climate, and geometry. Using the information collected, the most appropriate chemical treatment subcategories for a given situation can be selected from a series of charts and ranked using a simple equation. This process can be completed manually using a paper form, or by using a web-based tool. Matrices for each of the objectives were developed based on documented field experiments and the experience of a panel of practitioners. Guidance on specification language for procuring and applying unpaved road chemical treatments is also provided, along with comprehensive guidance on understanding unpaved road wearing course material performance.
    Posted 3/20/2018.
  • The Beguiling Science of Making Planet-Saving Pavement: Changing how we make the pavements we walk and drive on could make a real dent in California’s greenhouse gas emissions output, according to a Wired magazine article that cites UCPRC and its lifecycle studies. UC Davis Civil & Environmental Engineering Professors Alissa Kendall and John Harvey, Director of UCPRC, are both quoted: https://www.wired.com/story/pavement-environment-science.
    Posted 2/5/2018.
  • New Tech Memo Published: Performance Based Specifications: Literature Review on Increasing Crumb Rubber Usage by Adding Small Amounts of Crumb Rubber Modifier in Hot Mix Asphalt. “A comprehensive review of the literature covering more than 100 published journal articles, conference proceedings, and reports found that although considerable research has been undertaken to understand the advantages and disadvantages of using recycled tire rubber to modify asphalt binders, no published information on PG+X-type initiatives (i.e., focused more on using additional waste tires in asphalt mixes rather than on improving performance of the binder and mix) was found. A number of states ...”
    Posted 1/25/2018.
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Winter 2019 UCPRC Activities

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Candidate for fully permeable shoulder retrofit validation site

Mix Design Guidance Helps Contractors Meet Asphalt Performance Related Specifications. Caltrans has adopted mechanistic-empirical (ME) methods for flexible pavement design, and is using performance-related construction specifications on long-life rehabilitation projects for hot mix asphalt. Performance-related specifications (PRS) are used to help ensure that as-built materials meet the performance requirements assumed in ME pavement structural designs. For hot mix asphalt, producers need to meet specified values for stiffness, fatigue resistance, and rutting resistance. PRS pose new challenges for materials producers and contractors who have never had to relate volumetric mix design parameters to achievement of mechanistic parameters for fatigue life and rutting resistance based on results from performance-related laboratory tests.

The objective of this project was to provide guidance to mix designers and contractors to support their decision making regarding changes to mix designs to achieve PRS requirements. The initial guidance was prepared based on UCPRC experience supporting Caltrans and mix producers on previous AC Long-Life projects, and several decades of research experience. A Caltrans approved Superpave mix design was the starting point. A total of three sets of adjustments to this mix design were evaluated following the initial guidance and the effects on PRS laboratory test results were checked to see whether the guidance caused the expected improvements. The initial mix design guidance was found to be generally consistent with the laboratory test results for the example mix albeit with some minor exceptions. The mix design guidance was then revised based on findings from this study. It is recommended that the revised guidance be used on AC Long-Life projects or any projects where PRS are used, and that more data collected to make further improvements.

The mix design guidance report, which includes the flow chart for adjusting mixes to meet PRS on Page 9, is here.