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Open Access Publications from the University of California
Cover page of Lessons Learned from Caltrans Pilot Program for Implementation of EPDs

Lessons Learned from Caltrans Pilot Program for Implementation of EPDs


An environmental product declaration (EPD) is a transparent, verified report used to communicate the environmental impacts (e.g., resource use, energy, emissions) associated with the manufacture or production of construction materials such as asphalt, cement, asphalt mixtures, concrete mixtures, or steel reinforcement. EPDs, which are also called Type III Environmental Declarations, are product labels developed by industry in accordance with International Organization for Standardization standards. The scoping document for an EPD, which is also referred to as a product category rule (PCR), defines the requirements for EPDs for a certain product category. Beginning in 2019, Caltrans initiated a pilot study requiring EPDs for hot mix asphalt, aggregates, and concrete in addition to the materials specified by the Buy Clean California Act (BCCA) (Assembly Bill 262). The requirement to submit EPDs for these materials is how plans made several years prior to passage of the BCCA, for use of EPDs to help achieve environmental goals, are being implemented. While the BCCA considers only the greenhouse gas emissions contributing to global warming, the Caltrans pilot program for pavement and bridge materials also looks for other emissions in the EPDs, primarily emissions that cause air pollution. This project consisted of the University of California Pavement Research Center reviewing and helping develop Caltrans’s plans for collecting EPDs, reviewing PCRs and EPDs for consistency and inconsistencies, helping to communicate strategy with industries and the Federal Highway Administration, supporting Caltrans’s development of a web-based portal for entry of EPD data and the underlying database, and writing of a summary report. This technical memorandum is the summary report. This report documents the roadmaps developed for collecting and using EPDs, other support activities for the Caltrans EPD program, and a review of the EPDs supplied to Caltrans as of the summer of 2020 and their underlying PCRs. The PCRs for the materials in the Caltrans EPD program have inconsistencies that should be relatively simple to resolve with direction from Caltrans. In their current form, consistent data entry is difficult in the Caltrans EPD portal. To improve the consistency and quality of EPDs, Caltrans staff must receive guidance on how to review EPDs, and staff at materials producers require training about how to interpret PCRs to produce EPDs. Systems for inputting data from EPDs into department of transportation (DOT) reporting systems that include data quality checks, system consistency, and certification are also needed. Similarly, a nationally accepted and adopted data quality assessment standard is needed for EPDs as DOTs move toward their use in procurement. A single data quality matrix should also be included in a harmonized PCR.

Cover page of Pavement Environmental Life Cycle Assessment Tool for Local Governments

Pavement Environmental Life Cycle Assessment Tool for Local Governments


The processes in the pavement life cycle can be defined as: material extraction and production; construction; transport of materials and demolition; the use stage, where the pavement interacts with other systems; the materials, construction, and transport associated with maintenance and rehabilitation; and end-of-life. Local governments are increasingly being asked to quantify greenhouse gas emissions from their operations and identify changes to reduce emissions. There are many possible strategies that local governments can choose to reduce their emissions, however, prioritization and selection of which to implement can be difficult if emissions cannot be quantified. Pavement life cycle assessment (LCA) can be used by local governments to achieve the same goals as state government. The web-based software environmental Life Cycle Assessment for Pavements, also known as eLCAP has been developed a project-level LCA tool. The goal of eLCAP is to permit local governments to perform project-level pavement LCA using California specific data, including consideration of their own designs, materials, and traffic. eLCAP allows modeling of materials, transport, construction, maintenance, rehabilitation, and end-of-life recycling for all impacts; and in the use stage it considers the effects of combustion of fuel in vehicles as well as the additional fuel consumed due to pavement-vehicle interaction (global warming potential only). This report documents eLCAP and a project that created an interface for eLCAP that is usable by local governments.

Cover page of Concrete Overlay on Asphalt Pilot Project at Woodland SR 113: Construction

Concrete Overlay on Asphalt Pilot Project at Woodland SR 113: Construction


This report documents the design and construction of a concrete overlay on asphalt (COA) pavement on State Route 113 in Woodland, California, one of the first COA projects in the Caltrans road network. The project site extended over approximately 4 mi. of a two-lane secondary road. The concrete slabs were a half-lane wide (6×6 ft.) and 6 in. thick. The transverse joints were undoweled, but tie bars were installed at all the longitudinal joints. The outside slabs were 2 ft. wider than the interior slabs to provide a concrete shoulder. The project included a section with newly placed, rubberized, gap-graded asphalt mix base. A rapid-strength concrete mixture with Type II/V portland cement designed to be opened to traffic in 24 hours was used for construction of the overlay. The northern part of the project (PM 14.760 to PM 17.580) was built in October and November 2018, while the southern part (PM 11.860 to PM 12.890) was built in April and May 2019. The concrete mixture was produced in a fixed plant and transported in ready-mix trucks 25 mi. to the construction site. A slipform paver was used to consolidate and finish the concrete. A number of the quality control/quality assurance (QC/QA) tests and evaluations summarized in this report were conducted before, during, and after the construction of the concrete overlay. These QC/QA tests and evaluations revealed no major design or construction issues with the concrete overlay, but they did show that the condition of the asphalt base was very poor, particularly in the northern part of the project.

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

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


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 condition of concrete has an impact on mid- and long-term JPCP performance, very few studies have focused on determining what that impact is.

Cover page of Pavement ME Sensitivity Analysis (Version 2.5.3)

Pavement ME Sensitivity Analysis (Version 2.5.3)


The Mechanistic-Empirical Pavement Design Guide (MEPDG) is a comprehensive tool developed in 2002 by the American Association of State Highway and Transportation Officials (AASHTO) to analyze and design both flexible and rigid pavements. The models in the MEPDG are implemented in software called Pavement ME, a program calibrated using Long-Term Pavement Performance (LTPP) sections from throughout the United States, including some from California. The MEPDG recommends that nationally calibrated models be validated using local data, and if necessary, recalibrated, which makes sense when considering the climate and materials differences between California and the rest of the nation. The first step in recalibrating Pavement ME is to perform a sensitivity analysis to identify which variables are most important and to look for results that do not match expected performance. The factorial for the sensitivity analysis was designed to identify sensitivity and is not the factorial to be used for the development of design tools. This report presents the results of a sensitivity analysis showing the effects of design input variables controlled by the designer, and those not known to the designer. The sensitivity analysis shows that the overall jointed plain concrete pavements (JPCP) performance prediction by Pavement ME is reasonable. The distresses predicted by Pavement ME did not show any unexpected trends for any of the variables considered in this sensitivity analysis. Over the course of this study, no major issues were identified in running Pavement ME. The next steps are to complete the calibration using California pavement management system data and then to develop the design tool with the calibrated Pavement ME coefficients.

Cover page of Updates to CalME and Calibration of Cracking Models

Updates to CalME and Calibration of Cracking Models


The CalME flexible pavement simulation and design software program has been completely recoded as a web-based application calledCalME 3.0. CalME 3.0 retains the same incremental-recursive damage approach and the same forms for damage models and transferfunctions as CalME 2.0, which was validated using accelerated pavement testing data from Heavy Vehicle Simulator (HVS) test sectionsand the WesTrack experiment.The following enhancements and additions are all included in the revised program. First, the old software’s fatigue cracking transferfunctions for hot mix asphalt (HMA) on aggregate base, cement-stabilized bases, and portland cement concrete have been recalibratedusing a new approach for the calibration of mechanistic-empirical pavement design methods; this approach uses “big data” frompavement management systems, explicitly and separately considers between-project and within-project variability, and uses tens tohundreds of times more performance data than are used in conventional calibration methods. Second, the updated program also includesnew damage models and transfer functions for in-place recycling materials, including full-depth recycling (FDR) with foamed asphalt pluscement and cement stabilization, and partial-depth recycling (PDR) with emulsified asphalt and foamed asphalt plus cement. Third, theprogram now has been given the ability to model PDR using cold central plant recycled (CCPR) materials. Fourth, new damage modelshave been introduced for cement-stabilized bases and cement-stabilized and lime-stabilized subgrade materials to correct problems withthe models in CalME 2.0. Fifth, minimum aggregate base thicknesses were developed based on calculations of permanent deformationunder construction traffic. Lastly, simplified methods were developed for estimating subgrade stiffnesses (resilient modulus) based ondynamic cone penetrometer (DCP) tests, California bearing ratio (CBR) tests, and R-value tests.It is recommended that CalME 3.0 be implemented for pavement design, that the calibration be updated with new data approximatelyevery 3 to 5 years, that Caltrans traffic databases be checked before they are used again for recalibration, and that use of the recently updated Caltrans DIME database of as-built data be considered for future calibrations.

Cover page of First-Level Analysis of Heavy Vehicle Simulator Testing on Three RHMA-G Mixes to Investigate Performance with Reclaimed Asphalt Pavement Aggregate Replacement

First-Level Analysis of Heavy Vehicle Simulator Testing on Three RHMA-G Mixes to Investigate Performance with Reclaimed Asphalt Pavement Aggregate Replacement


This technical memorandum summarizes a literature review update, elements of the construction of a test track to assess various aspects of gap-graded rubberized asphalt concrete (RHMA-G) mixes with and without the addition of reclaimed asphalt pavement (RAP) as aggregate replacement, and a first-level analysis of the results from the first three Heavy Vehicle Simulator (HVS) tests.

Four different RHMA-G mixes were placed on seven sections on the test track at the UCPRC. Mixes differed by nominal maximum aggregate size (NMAS, 1/2 and 3/4 in.) and the addition of 10% RAP by weight of the aggregate as an aggregate replacement. Single and double lifts of each mix were placed. Apart from the addition of RAP, the mix designs all met current Caltrans specifications. Although Caltrans currently does not permit more than one lift of RHMA-G on projects, the placement of each lift of each mix on the test track met current Caltrans specifications for RHMA-G layers.

The first three HVS tests discussed in this technical memorandum covered the control section (0.2 ft. [60 mm], 1/2 in. NMAS with no RAP), a section with a single lift of 1/2 in. mix with RAP, and a section with two lifts of a 3/4 in. mix with RAP. Results from these first three HVS tests, which focused on rutting performance, indicated the following:

• Performance of all three mixes was satisfactory in terms of the level of trafficking required to reach a terminal average maximum rut of 0.5 in. (12.5 mm).

• The addition of RAP as a coarse aggregate replacement did not appear to have a significant influence on the test results.

• The back calculated stiffnesses of the RHMA-G layer(s) on each section before and after HVS testing indicate that the trafficking did not cause any significant damage (i.e., loss in stiffness) in any of the three test sections. Stiffnesses increased after trafficking on two of the three sections, which was attributed to a combination of aging and densification of the layers under traffic. Some blending of reclaimed asphalt binder with the asphalt rubber binder over time on these two sections, both containing RAP, may have contributed to this stiffness increase.

• No cracks were observed on any of the sections after trafficking.

Given that only three sections have been tested to date, no recommendations on RHMA-G layer thicknesses or permitting the use of coarse RAP in RHMA-G mixes can be made at this time. These recommendations will be made after all the sections have been tested and the forensic investigations and associated laboratory testing have been completed.

Cover page of Effects of Increased Weights of Alternative Fuel Trucks on Pavement and Bridges

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 long-haul vehicles, for which range issues arise with EVs and FCs. But the estimates predicted that by 2050, alternative fuels would power 25–70% of long-haul and 40–95% of short-haul and medium-duty trucks. AFT implementation is expected to be focused in the 11 counties with the greatest freight traffic—primarily urban counties along major freight corridors. Results from the implementation scenarios suggest that introducing heavier AFTs will only result in minimal additional pavement damage, with its extent dependent on the pavement structure and AFT implementation scenario. Although allowing weight increases of up to 2,000 lbs. is unlikely to cause major issues on more modern bridges, the effects of truck concentrations at those new limits on inadequate bridges needs more careful evaluation. The study’s most aggressive market penetration scenario yielded an approximate net reduction in annual well-to-wheel truck propulsion emissions of 1,200–2,700 kT per year of CO2 -e by 2030, and 6,300–34,000 kT by 2050 versus current truck technologies. Negligible effects on GHG emissions from pavement maintenance and rehabilitation resulted from AFT implementation.

Cover page of Development of Performance-Based Specifications for Asphalt Rubber Binder: Interim Report on Phase 1 and Phase 2 Testing

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 and viscosity are used as acceptance of quality control; however, these parameters do not necessarily provide a satisfactory link between the measured binder properties and potential performance in the field over a range of operating temperatures. In California, current specifications require that crumb rubber particles used to produce asphalt rubber binder in the “wet process” must be smaller than 2.36 mm (i.e., 100 percent passing the #8 sieve), and typically these particles vary in size between 1 mm and 2 mm. Consequently, when the parallel plate geometry is used to test this type of binder, the larger incompletely digested rubber particles can contact the plates. If this occurs, the rubber particle rheology can potentially dominate the results, which in turn may not be representative of the modified binder as a whole. To address this problem, a potentially more appropriate DSR testing protocol using concentric cylinder geometry was investigated in Phase 1 of this study to explore an alternative means of determining the performance properties of asphalt rubber binders. Phase 2 of the study, documented in this report, continued the investigation into the use of the concentric cylinder geometry and alternate parallel plate geometry with a 3-mm gap. The use of these geometries for intermediate-temperature testing and multiple stress creep recovery testing was also investigated, along with modified procedures for short- and long-term aging in the rolling thin-film oven and pressurized aging vessel, respectively, and specimen preparation procedures for bending beam rheometer (BBR) testing. Limited mix testing was also conducted to relate high- and low-temperature mix performance to the performance grades determined for the binders used in the mixes. The concentric cylinder testing approach to measuring the rheological properties of asphalt rubber binders is considered feasible, and that with its use, the edge effects and trimming issues associated with parallel plate testing can be eliminated. However, the concentric cylinder method requires a longer testing time and a larger binder sample than the parallel plate test method. Initial findings from performance grading and related mix testing indicate that the incompletely digested rubber particles, which have different sensitivities to temperature and applied stress and strain than the asphalt binder, appear to dominate the test results. This will need to be factored into analyses and interpretation of rheology and mix performance test results. The proposed modifications to the short- and long-term aging procedures and to the BBR specimen preparation procedures are considered to be more aligned with the original intent of the tests and will likely reduce the variability between replicate specimens during testing. The results from Phase 2 support the continuation of testing, which should be in line with the original workplan and objectives of this research effort. The research should continue to refine the testing procedures on additional field binder sources, assess the repeatability and reproducibility of any proposed test methods, and evaluate the applicability of the results to the actual performance properties of mixes produced with asphalt rubber binders.

Cover page of Life Cycle Assessment and Life Cycle Cost Analysis for Six Strategies for GHG Reduction in Caltrans Operations

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 in operating the California (CA) state highway network and other transportation assets so it can help meet the state’s GHG reduction goals. Although many GHG reduction strategies appear to be attractive, simple, and effective, most also have limitations, trade-offs, and unintended consequences that cannot be identified without a preliminary identification and examination of the full system they operate in and their full life cycle. To achieve the most rapid and cost-effective changes possible, the costs, times to implement, and difficulty of implementation should also be considered when the alternative strategies are being prioritized. This project first developed an emissions reduction “supply curve” framework by using life cycle assessment (LCA) to evaluate full-system life cycle environmental impacts and life cycle cost analysis (LCCA) to prioritize the alternative GHG-reduction strategies based on benefit and cost. This framework was then applied to an example set of strategies and cases for Caltrans operations. This technical memorandum presents the results of the supply curve framework’s development and its application to six strategies for changing several Caltrans operations identified by the research team. The six strategies were: (1) pavement roughness and maintenance prioritization, (2) energy harvesting using piezoelectric technology, (3) automation of bridge tolling systems, (4) increased use of reclaimed asphalt pavement, (5) alternative fuel technologies for the Caltrans vehicle fleet, and (6) solar and wind energy production on state right-of-ways. A summary of the methodology and the resulting supply curve that includes all the strategies considered and ranked is published in a separate white paper. This technical memorandum provides the details, assumptions, calculation methods, and results of the development of the GHG reduction supply curve for each strategy. Although this current study’s scope is limited to development of a supply curve for GHG emissions only, there are plans to expand the study’s scope to include other environmental impacts and to develop supply curves for them as well.