Recent itsdavis_ucprc_techmemos items

2025 Condition Survey of High RAP Pilot Projects on El Dorado 49, San Bernardino 215, and San Joaquin 26

Wed, 17 Jun 2026 00:00:00 +0000

Three pilot projects were constructed using hot mix asphalt (HMA) with higher percentages of recycled asphalt pavement (RAP) (25% to 40%) and recycled asphalt shingles (RAS) used at 0% or 3%. The three projects were paved between 2021 and 2022 on State Route 49 in El Dorado County (ED 49), State Route 215 in San Bernardino County (SBD 215), and State Route 26 in San Joaquin County (SJ 26). Two and a half to three years later, pavement condition surveys were conducted to observe surface distresses. On ED 49, the 3% RAS mix exhibited 6% low-severity wheelpath alligator cracking, often with mild pumping. The other mixes on ED 49 exhibited lower levels of alligator and total cracking. No alligator cracking was observed on SBD 215, which includes a cement-treated base not present in the other pilot projects. On SJ 26, all test sections exhibited some form of cracking, though mostly of low severity. Among the mixes, the 25% RAP/3% RAS mix showed the most alligator cracking on SJ 26...

RAP and RAS in HMA Pilot Project on SJ 26: Material Testing, Observations, and Findings

Tue, 9 Jun 2026 00:00:00 +0000

A pilot project for the inclusion of high percentages of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) in hot mix asphalt (HMA) was built on State Route 26 in San Joaquin County in September 2022. Six mixes were included in short test sections: (1) a control mix with no RAS or RAP, (2) a mix with 25% RAP and recycling agent (RA) (3) a mix with 30% RAP and RA, (4) a mix with 35% RAP and RA, (5) a mix with 40% RAP and RA, and (6) a mix with 25% RAP, 3% RAS, and RA. A seventh mix, which was a typically used mix with 12% RAP and no RA, was used for construction of the rest of the overall project. This technical memorandum presents the laboratory test results from plant mix produced for job mix formula verification and from one or two quality assurance (QA) samples, depending on the test, taken during test section construction, as well as observations of plant production and construction. None of the mixes passed the Delta Tc specification, which is not uncommon...

Performance Evaluation of Recycled and Virgin Fibers in Fiber-Reinforced Concrete for Pavement Applications—Laboratory Test Results

Mon, 8 Jun 2026 00:00:00 +0000

This study evaluates the performance of recycled and virgin fibers in fiber-reinforced concrete (FRC), with a focus on workability, concrete production, and mechanical properties. Fibers were directly sourced from manufacturers and used at dosages recommended by manufacturers and supported by the literature. All fibers improved the modulus of rupture of plain (control) concrete. The fibers investigated included plastic, steel, composite, glass, and basalt fibers. Across most fiber types—regardless of whether they were virgin or recycled—FRC demonstrated improved post-cracking load-carrying capacity, resulting in enhanced residual strength and ductility. Plastic fibers exhibited the best post-cracking performance, with high residual strength, toughness, and effective flexural strength ratios, though they reduced workability. Recycled plastic fibers performed comparably to virgin plastic fibers in terms of post-cracking behavior. Steel fibers had minimal impact on workability and...

Preliminary Assessment of Effects of Gross Vehicle Weight Limit Increases for Trucks on Pavement Life and Cost

Mon, 18 May 2026 00:00:00 +0000

In January 2022, the Caltrans Pavement Program asked the University of California Pavement Research Center (UCPRC) to provide a quick high-level estimate of the effects of gross vehicle weight limit increases for trucks on pavement performance and the associated impact on the costs of pavement maintenance (Maintenance budget) and rehabilitation (SHOPP budget). Caltrans is considering increasing the limit from current 80 kips to 88 kips. This technical memorandum was delivered in February 2022. It was updated based on Caltrans comments in the same month and used internally by Caltrans but was not published. In September 2024 the Pavement Program requested that the UCPRC publish the technical memorandum. The results show that the high-level estimate is that the Maintenance and SHOPP budgets for pavement will need to increase by approximately 6% over the current projected 10-year total cost of $20.2 billion, resulting in a 10-year total increase of approximately $1.2 billion.

Twenty-Year Performance Review of Asphalt Concrete Long-LifePavements with Performance-Related Specifications

Wed, 18 Mar 2026 00:00:00 +0000

The first asphalt concrete long-life (AC Long Life) project was constructed in Los Angeles County on Route 710 (LA-710) near Long Beach in 2001/2004 and is now over 20 years old. Four more AC Long Life projects have been completed in California since then, three between 2011 and 2014 (TEH-5, SIS-5, SOL-5), and one in 2021/2022 (SAC-5). The goal of these AC Long Life projects was to achieve design lives of 30 years or 40 years (the standard Caltrans asphalt pavement design life was 20 years at the time). Measures taken to achieve those lives included the use of performance-related specifications for job mix formula approvals, higher compaction requirements, and the use of a three-layer asphalt concrete system for structural capacity. These measures required additional costs. Calculations indicate that the longer lives will result in life cycle cost reductions if they achieve the design lives. Hence, periodic performance evaluations are important, which is the purpose of this technical...

RAP and RAS in HMA Pilot Project on SBD 215: Material Testing, Observations, and Findings

Tue, 17 Feb 2026 00:00:00 +0000

A pilot project for the inclusion of high percentages of reclaimed asphalt pavement (RAP) in hot mix asphalt (HMA) was built on State Route 215 in San Bernardino County in September 2022. Five mixes were included in short test sections: (1) a control mix with no recycled asphalt shingles (RAS) or RAP, (2) a mix with 25% RAP and recycling agent (RA), (3) a mix with 30% RAP and RA, (4) a mix with 35% RAP and RA, and (5) a mix with 40% RAP and RA. A sixth mix, which was a typically used mix with 23% RAP, was used for construction of the rest of the overall project. This technical memorandum presents the laboratory test results from plant mix produced for job mix formula verification and from one or two quality assurance (QA) samples, depending on the test, taken during test section construction as well as observations of plant production and construction. Only the control mix binder consisting of the virgin PG 64-28M base binder and the mix with PG 58-34M, 25% RAP, and RA passed...

Development of Thin Bonded Concrete Overlay of Asphalt Design Method: Evaluation of Existing Mechanistic-Empirical Design Methods

Sun, 10 Aug 2025 00:00:00 +0000

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 BCOA design method, this technical memorandum includes an evaluation of two existing mechanistic-empirical methods: BCOA-ME, developed by the University of Pittsburgh, and MEPDG, as implemented in Pavement ME Design versions 2.3 (2016) and later. The evaluation includes a sensitivity analysis that considered the most important factors...

Test Method Selection and Validation to Replace the R-Value Test

Thu, 29 May 2025 00:00:00 +0000

This technical memorandum summarizes a study that investigated the use of a confined compressive strength (CCS) test to replace the R-value test currently used for some pavement design and for quality control/quality assurance in California. The report covers a literature review, development of an alternative test, and a comparison of the results from the proposed test with R-value results.

The following are conclusions made based on the findings. First, California Test 216 needs revision. The compaction density reported by the test method is lower than the physical density of the compacted specimen in the CT 216 apparatus. The reported CT 216 density is approximately 88% of Modified Proctor density. Second, the proposed specimen compaction procedure, using Modified Proctor as the reference density, produced unbound specimens that could be handled and tested in a triaxial cell. Third, there is no correlation between the R-value test and the CCS test for the materials...

Literature Review and Industry Survey of Recycled Fibers from Novel and Existing Source Materials for Concrete Use

Mon, 7 Apr 2025 00:00:00 +0000

Research has demonstrated the multiple benefits of fibers for the early and late-age performance of concrete pavements and bridge decks. Many research studies have also shown that the expected enhancements in properties of concrete with recycled fibers could be commensurate with those of concrete reinforced with virgin fibers. However, compared with virgin polymeric fibers and steel fibers from primary steel, recycled fibers and fibers from natural sources are not as commonly implemented in construction due to several barriers. Some of these obstacles include a lack of research on recycled fibers, leading to gaps in technical performance data, case studies, test tracks, and pilot projects. The primary reason for the lack of research is related to gaps in information regarding the quality of recycled fibers compared to virgin fibers. To help overcome some of these barriers, this study included a comprehensive survey of concrete fiber suppliers. Those suppliers with recycled fiber...

State Route 138: Test Site Evaluation Update of Evaluation Activities in March and October 2002

Wed, 26 Mar 2025 00:00:00 +0000

In 2001, Caltrans Maintenance selected a segment of State Route 138 in Los Angeles County to create test sections for the evaluation of pavement/tire noise measurements and performance of several maintenance treatments. In March 2001, the Caltrans Partnered Pavement Research Center (PRC) Contract Team (staff from University of California Pavement Research Center and Dynatest Consulting Inc.) collected and analyzed pavement data from the segment, and recommended test section locations that would provide the most uniform underlying pavement structures possible.(1) The objective of identifying uniform underlying pavement structures was to provide the most unbiased evaluation possible of the performance of the various treatments.The data used to select the sections included:- Visual surface condition survey to identify existing distresses,- Deflection testing using a Falling Weight Deflectometer (FWD) and accompanying deflection analysis and back-calculation of stiffnesses,- Coring...

Durability Testing of LCB and CTB Materials Supplied by Caltrans

Wed, 26 Mar 2025 00:00:00 +0000

Carbonation of cement-stabilized layers under concrete pavements in California was investigated as a potential reason for faulting of these pavements. In discussions with personnel from the Pavement Research Center, it was mentioned that a layer of loose material is often observed between the concrete slab and the supporting cement stabilized layer. Samples of materials commonly used under concrete slabs were sent to South Africa for durability testing using South African test methods. These test methods were primarily developed at the CSIR, Transportek, for the purpose of durability assessment of stabilized materials. The materials supplied by Caltrans consisted of samples of two aggregates used to make cement treated base (CTB) and lean concrete base (LCB). The aggregate sources for these materials were, named Mission Valley and Lake Herman. Details of gradings, water content, and cement content were provided with the samples. These materials were tested for durability using...

Evaluation of Recycled Asphalt Concrete Materials as Aggregate Base

Wed, 26 Mar 2025 00:00:00 +0000

This technical memorandum summarizes the evaluation of a rehabilitation strategy that involves recycling an existing asphalt concrete surface and a portion of the base material into a new base layer. A series of field and laboratory tests were conducted to evaluate this rehabilitation strategy. Field tests included destructive and non-destructive testing conducted on a pavement section located on California State Highway 395 between PM 13 and PM 10, which is about 10 miles south of Alturas, CA. For purposes of analysis and discussion, the starting station is 0.0 (m) at PM 13 and the ending station is 4800.0 (m) at PM 10. The recycling process was conducted between stations 0.0m and 3125.0 m. Laboratory tests included static and dynamic tests on the recycled asphalt concrete and two California aggregate base class 2 materials.The objectives of the study are (1) to evaluate the performance of the recycling process in the field by analyzing destructive and non-destructive data before...

Development of Hot Mix Asphalt Pavement Performance Properties for Long-Life Pavement Design: Caltrans District 4, Interstate-80 Solano County, California

Wed, 5 Mar 2025 00:00:00 +0000

In the period 2012 to 2014 Caltrans designed and built three long-life asphalt pavement (LLAP) rehabilitation projects. Two projects were in District 2 on Interstate 5—one just north of the city of Red Bluff and the other on the interstate running through and north of the city of Weed—and one in District 4 on Interstate 80 in Solano County between the cities of Dixon and Vacaville. This technical memorandum describes the processes by which performance criteria were developed for a pavement section that is part of the LLAP project on Interstate 80. This pavement section, designed and constructed as an LLAP section, consisted of the following pavement components: A hot mix asphalt (HMA) surface course containing a polymer-modified asphalt (PG 64-28PM) with 15 percent reclaimed asphalt pavement (RAP) and a representative virgin aggregate from the local area treated with 1.2 percent lime (marinated). An HMA intermediate course containing a conventional asphalt binder (PG 64-10), and...

Early-Age and Premature Cracking in Jointed Plain Concrete Pavements: Literature Review

Mon, 3 Mar 2025 00:00:00 +0000

This technical memorandum includes a literature review about the factors that may lead to early-age and premature cracking of jointed plain concrete pavements (JPCPs). The review shows that many factors are involved and that many different circumstances can result in these types of cracking. In most of the cases reported in the literature, the early-age and premature cracking were related to poor construction practices. The early-age cracking of JPCP has already received considerable attention, and there is agreement regarding the mechanisms that result in this type of cracking and about the practices recommended to reduce it. The current version of the Caltrans Standard Specifications addresses most of these practices, but Caltrans specifications for paving in adverse weather conditions are not completely clear. Unlike the causes of early-age cracking on JPCP, premature cracking of JPCP has not been studied extensively. Further, even though it is widely recognized that the early-age...

Performance Based Specifications: Literature Review on Increasing Crumb Rubber Usage by Adding Small Amounts of Crumb Rubber Modifier in Hot Mix Asphalt