Dedicated to providing knowledge, the Pavement Research Center uses innovative
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NEWS (Previous News Items)

  • Upcoming Symposium, January 12-15, 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 1/4/2021.
  • New Research Report Published: Effects of Increased Weights of Alternative Fuel Trucks on Pavement and Bridges. “California’s truck fleet composition is shifting to include more natural gas vehicles (NGVs), electric vehicles (EVs), and fuel cell vehicles (FCVs), and it will shift more quickly to meet state greenhouse gas (GHG) emission goals. These alternative fuel trucks (AFTs) may introduce heavier axle loads, which may increase pavement damage and GHG emissions from work to maintain pavements. This project aimed to provide conceptual-level estimates of the effects of vehicle fleet changes on road and bridge infrastructure. Three AFT implementation scenarios were analyzed using typical Calif. state and local pavement structures, and a federal study’s results were used to assess the effects on bridges. This study found that more NGV, EV, and FC trucks are expected among short-haul and medium-duty vehicles than among...”
    Posted 1/4/2021.
  • New Policy Brief Published: Heavier Alternative Fuel Trucks Are Not Expected to Cause Significant Additional Pavement Damage. “Medium- and heavy-duty trucks on California’s roads are shifting from conventional gasoline and diesel propulsion systems to alternative fuel (natural gas, electric, and fuel cell) propulsion technologies, spurred by the state’s greenhouse gas (GHG) reduction goals. While these alternative fuel trucks produce fewer emissions, they are also currently heavier than their conventional counterparts. Heavier loads can cause more damage to pavements and bridges, triggering concerns that clean truck technologies could actually increase GHG emissions by necessitating either construction of stronger pavements or more maintenance to keep pavements functional. California Assembly Bill 2061 (2018) allows a 2,000-pound gross vehicle weight limit increase for near-zero-emission vehicles and zero-emission vehicles to enable these trucks to carry the same loads as their conventional counterparts. The law also asked the UC Institute...”
    Posted 1/4/2021.
  • Fall 2020 Kent Seminar Led by UCPRC Director John Harvey: Improving Pavement Sustainability Through Integrated Design, Construction, Management, LCA and LCCA. On September 28, 2020, UCPRC director, Prof. John Harvey, delivered an online address to an audience at the Illinois Center for Transportation. His discussion focused on how to improve pavement sustainability through a broad approach that considers integrated design, construction, management, LCA, and LCCA. In his presentation, Prof. Harvey laid out the UCPRC research road map and the UCPRC research, development, and implementation vision he put together 20 years ago. He provided specific examples—including the use of CalME and performance-related specifications to design and implement long life asphalt pavements. He also talked about the use of LCCA and LCA to support state and local government decisions to evaluate alternative technologies to improve sustainability.
    Posted 12/9/2020.
  • New Tech Memo Published: Life Cycle Assessment and Life Cycle Cost Analysis for Six Strategies for GHG Reduction in Caltrans Operations. “California state government has established a series of mandated targets for reducing the greenhouse gas (GHG) emissions that contribute to climate change. With a multiplicity of emissions sources and economic sectors, it is clear that no single change the state can make will enable it to achieve the ambitious goals set by executive orders and legislation. Instead, many actors within the state’s economy–including state agencies such as the California Department of Transportation (Caltrans)–must make multiple changes to their own internal operations. The focus of this study and technical memorandum is to examine several strategic options that Caltrans could adopt to lower its GHG emissions...”
    Posted 10/8/2020.
  • New Research Report Published: Development of Performance-Based Specifications for Asphalt Rubber Binder: Interim Report on Phase 1 and Phase 2 Testing. “In the United States, the Superpave Asphalt Binder Performance Grading (PG) system proposed by the Strategic Highway Research Program (SHRP) is the most common method used to characterize the performance-related properties of unmodified and polymer-modified asphalt binders. Dynamic shear modulus (G*) and phase angle (δ) are the two main binder properties and they are measured using a dynamic shear rheometer (DSR) with parallel plate geometry and either a 1-mm or 2-mm gap between the plates. Since these Superpave parameters were developed for binders that do not contain additives or particulates, the California Department of Transportation (Caltrans) does not use them for asphalt rubber binder specifications. Instead, penetration...”
    Posted 10/8/2020.
  • New Research Report Published: Optimizing Rubberized Open-graded Friction Course (RHMA-O) Mix Designs for Water Quality Benefits: Phase I: Literature Review. “Historically, rubberized and non-rubberized open-graded friction courses (OGFCs) have been placed to provide three benefits: to increase traffic safety, to reduce urban highway noise, and to preserve the surface of the main pavement structural section. However, stringent environmental regulations on stormwater runoff management enacted recently have forced transportation agencies with limited right of ways in urban areas to search for creative methods to treat runoff and receive credits for preventing pollution from highways. This literature review was undertaken to explore ways to optimize current RHMA-O mix designs...”
    Posted 9/16/2020.
  • Caltrans/UCPRC Asphalt PRS Road Map: Performance Related Specifications for Asphalt Superpave and QC/QA. The Caltrans/UCPRC road map for development of performance related specifications (PRS) for asphalt pavement materials, integrated with mechanistic-empirical (ME) design and balanced mix design, was discussed at the Federal Highway Administration stakeholder workshop (August 11-13, 2020) on this subject. Stakeholders at the workshop were FHWA, state DOTs, the asphalt pavement industry, and university researchers.
    Posted 8/13/2020.
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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.