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116425, The objective of this study was to evaluate the influence of production variability on performance test results to determine if mixtures balanced during design could become unbalanced during production. Fourteen currently accepted mixture designs, 10 BMD mixtures and 4 Superpave mixtures (to serve as a comparison between current standards and BMD designs), were recreated in the laboratory. Additionally, the mixes were adjusted to produce coarse and fine gradations and high and low binder contents according to currently accepted tolerance limits to simulate production variability. Two interaction mixtures assessing changes in gradation and binder content were evaluated as well as two critically aged mixtures.

119857, The Virginia Department of Transportation (VDOT) has been working toward the implementation of balanced mix design (BMD) for several years. During that time, special provisions have been developed to address dense-graded surface mixtures with reclaimed asphalt pavement (RAP) contents up to 30% and with RAP contents of 40% and above. In 2020, five field trials encompassing 12 mixtures were constructed to evaluate BMD mixtures designed and produced in accordance with VDOT’s special provision for surface mixtures with high RAP contents. Typical dense-graded Superpave surface mixtures were used as controls. This study documented and assessed these trials to provide information to evaluate the impact of various RAP contents and additives, production variability, reheating, and binder properties on BMD performance test results. Twelve mixtures were evaluated during the five field trials. The mixtures included combinations of different RAP contents, two binder grades, four recycling agents, and fiber. Volumetric and gradation analysis was performed on the mixtures. The Cantabro mass loss test (Cantabro test), the indirect tensile cracking test (IDT-CT), and the Asphalt Pavement Analyzer (APA) test were performed on laboratory-produced design specimens and non-reheated and reheated plant-produced, laboratory-compacted specimens. All findings and conclusions are limited to the mixtures evaluated. Based on the test results, mixtures containing 35% or greater RAP contents, softer binders, recycling agents, and fiber may be designed and produced to meet current BMD performance thresholds and current volumetric properties, gradation, and asphalt content requirements. It was found that some mixtures that were volumetrically designed under current VDOT specifications met BMD requirements. In addition, the expected trends in mixture performance testing were not always observed, likely due to masking by variability due to specimen fabrication practices or by inherent test variabilit

119819, Many state highway agencies are currently exploring a new approach for designing and accepting asphalt mixtures, known as the balanced mix design (BMD) method (hereinafter “BMD”). The Virginia Department of Transportation (VDOT) has made a commitment to adopt BMD to enhance the performance of asphalt mixtures. Since 2018, VDOT has taken incremental steps to phase in the use of BMD in production while addressing concerns expressed by VDOT and the industry. The use of BMD line items in selected 2021 and 2022 contracts has been an important learning opportunity for VDOT and the industry along the path to implementation. This study documented and assessed the 2021 and 2022 maintenance plant mix schedule pilots. The objectives of the study were to provide information on quality control, acceptance testing, and independent assurance testing; analyze the performance properties of reheated mixtures and extracted and recovered binders; and document lessons learned from the process. The analysis addressed several topics, including variability in production and testing and binder characterization and implications for performance. The pilot projects were developed by the VDOT districts using maintenance plant mix schedule contracts. In 2021, approximately 72,000 tons of BMD mixtures were paved on selected routes in 10 maintenance schedules across five districts. In 2022, approximately 222,000 tons of BMD mixtures were paved in 13 maintenance schedules distributed across all nine VDOT districts, with at least one BMD contract executed per district. The Cantabro mass loss test, the indirect tensile cracking test (IDT-CT), the Asphalt Pavement Analyzer rut test, and the indirect tensile test at high temperature (IDT-HT) were performed on laboratory-produced design specimens and non-reheated and reheated plant-produced, laboratory-compacted specimens. Basic and advanced binder testing and analysis were conducted on extracted and recovered binders from selected samples of the mixtur

119604, This study assessed the short-term functional (surface) characteristics of pavements constructed using dense-graded asphalt surface mixtures designed with the balanced mix design (BMD) methodology as compared to counterpart mixtures designed using the existing design methodology (Superpave). Another objective of this study was to establish a functional performance baseline for the Virginia Department of Transportation’s (VDOT) BMD trial mixtures constructed in the 2019 through 2021 construction seasons in terms of friction and macrotexture. This study also sought to define a potential empirical relationship to link mixture volumetric properties to the surface characteristics of asphalt mixtures in terms of macrotexture. In this effort, 52 different field projects encompassing pairs of BMD and control mixtures with service lives ranging from 0.1 to 2.8 years were surveyed for friction, macrotexture, and pavement roughness. Descriptive statistics and parametric statistical techniques were used to identify systematic trends or differences in the functional characteristics of the pavements.