Browsing by Author "Habbouche, Jhony"

Now showing 1 - 4 of 4
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    Assessment of the Production Variability and Composite Performance Index for Conventional and High Reclaimed Asphalt Pavement Balanced Mix Design Mixtures
    Tong, Bilin; Habbouche, Jhony; Diefenderfer, Stacey D.; Flintsch, Gerardo W.; Boz, Ilker (Sage, 2024-11-08)
    The balanced mix design (BMD) concept enables the design of engineered mixtures containing conventional and high reclaimed asphalt pavement (HRAP) contents, moving beyond the constraints of traditional volumetric design methodologies. During production, the designed mixture undergoes verification and potential modifications at the plant to accommodate actual production and field circumstances, regardless of the mix design method. This study assessed the impact of production and associated performance variability on a volumetrically designed control mixture and five mixtures designed with the BMD concept. This investigation showed relatively precise gradation control, but exceedances of volumetric property tolerances were observed in BMD-optimized mixtures during production. Performance, including durability, cracking, and rutting susceptibility, was evaluated using the Cantabro test, indirect tensile cracking test (IDT-CT), and asphalt pavement analyzer (APA) test, respectively. Test results uncovered that produced mixtures may become unbalanced. Observations from the Cantabro test and IDT-CT highlighted the necessity and effectiveness of employing the BMD for HRAP mixtures. The potential aging effect introduced during the reheating process may compromise durability and cracking resistance. In addition, a three-dimensional plot with a revised composite performance index (CPIR) was used to optimize the process of evaluating the mixture “balance” status among multiple primary performances. It revealed that almost all produced HRAP mixtures demonstrated a well-balanced status. Finally, agencies can use the CPIR as part of their acceptance program for BMD mixtures to determine a pay factor for possible bonuses or penalties.
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    Evaluation of Balanced Asphalt Surface Mixtures with Conventional and High RAP Contents Using Laboratory and Accelerated Pavement Testing
    Tong, Bilin (Virginia Tech, 2025-01-22)
    Balanced Mix Design (BMD) represents an asphalt mixture design methodology that replaces certain traditional volumetric parameters with performance-based testing to address predominant distresses such as rutting and cracking. This approach offers an avenue to properly design and produce engineered asphalt mixtures, including those with high reclaimed asphalt pavement (HRAP) contents, recycling agents (RAs), fibers, and polymer-modified binders. Laboratory performance tests are essential to the BMD process, as they ensure the production of durable, high-performance materials. Beyond laboratory performance evaluation, accelerated pavement testing (APT) plays a crucial role in bridging the gap between laboratory material characterization and field pavement performance. This dissertation aimed to assess the BMD concept for designing durable, long-lasting surface mixtures in Virginia, with particular emphasis on higher RAP content mixtures (HRAP mixtures, i.e., exceeding 30% RAP). The study involved laboratory and APT testing of six surface mixtures featuring a range of RAP contents (both conventional and high), two binder grades (PG 64-22 and PG58-28), one RA, and one warm mix additive. Findings indicated that dense-graded, unmodified surface mixtures with higher RAP contents can be successfully designed using the current Virginia Department of Transportation (VDOT) BMD special provision. These mixtures can be produced in the plant with no significant deviations in aggregate gradation and asphalt binder content from the design specifications. The combined effect of variations in different volumetric properties during production may influence the primary performance of the mixtures, potentially resulting in an imbalance. As a consequence, the produced BMD mixture may fail to meet one or more performance thresholds. Additionally, the results underscored the effectiveness of BMD concept with incorporating RAs and/or a softer binder when designing HRAP surface mixtures. Importantly, the current selected BMD tests characterized the laboratory performance of mixtures, aligning with the performance observed under APT. This research provided a steppingstone towards the examination and validation of the VDOT BMD thresholds, which ensures satisfactory field performance. The study also indicated that while current BMD thresholds provided sufficient margins for satisfactory field cracking performance, rutting resistance may become a concern for overly designed BMD HRAP mixtures. For instance, mixtures with excessively high asphalt binder content may exhibit compromised rutting resistance. Furthermore, to address the challenges uncovered during BMD test analysis—issues like the constraints of traditional pair-wise comparisons, risks of repetitive design processes, and the difficulty in pinpointing critical factors in mixture production—this dissertation proposed innovative solutions to enhance BMD application and streamline the evaluation process. First, a novel Composite Performance Index (CPI), visualized through a 3D plot, captured the "balance" status of various mixtures. Second, a machine learning-enhanced BMD framework was introduced, offering intelligent optimization throughout the design and production phases. The integration of these two tools offers significant potential for simultaneously improving multiple performance indices of asphalt mixtures. Finally, this research demonstrated that the performance of higher RAP content mixtures can exceed that of lower RAP content mixtures through the application of BMD approaches. This dissertation not only advanced the implementation of BMD for surface mixtures but also contributed to the sustainable and performance-driven evolution of asphalt mix design. The insights gained from this study provided practical guidance and strategic recommendations for enhancing asphalt mixture design, production, and performance monitoring.
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    Multi-level performance evaluation of BMD surface mixtures with conventional and high RAP contents: a case study in Virginia
    Tong, Bilin; Habbouche, Jhony; Diefenderfer, Stacey D.; Flintsch, Gerardo W. (Taylor & Francis, 2024-03-07)
    This study investigated one control and five Balanced Mix Design (BMD) optimised asphalt surface mixtures, four of which had high reclaimed asphalt pavement (RAP) contents (HRAP mixtures), using laboratory performance tests characterised with different levels of complexity. The performance of the evaluated mixtures was assessed based on durability, rutting resistance, and cracking resistance as emphasized by BMD. The study explored the ranking of a single index and correlations among various indices. Assisted by 3-Dimensional and ternary plots, this study also proposed a novel composite performance index [CPI] that combines major indices (durability, cracking, and rutting) to evaluate the performance of BMD optimised mixtures. The results revealed discrepancies between basic/intermediate performance test results and advanced performance test results. The comparisons conducted also underscored the beneficial impacts derived from using softer binders and/or recycling agents in HRAP mixtures. Furthermore, the findings indicated that the BMD approach can serve as an effective framework for designing asphalt mixtures that simultaneously enhance both fatigue and rutting performance. Moreover, the study revealed HRAP BMD surface mixtures can exhibit superior overall performance when compared to conventionally designed control mixtures.
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    Rutting Performance Evaluation of BMD Surface Mixtures with Conventional and High RAP Contents under Full-Scale Accelerated Testing
    Tong, Bilin; Habbouche, Jhony; Flintsch, Gerardo W.; Diefenderfer, Brian K. (MDPI, 2023-12-12)
    The balanced mix design (BMD) constitutes a significant step forward in the pursuit of better-performing asphalt mixtures. This approach/framework offers increased innovative opportunities for the proper design and production of engineered asphalt mixtures without the need to strictly adhere to traditional volumetric requirements. The primary objective of this paper is to conduct a comprehensive investigation of the permanent deformation (rutting) behavior of surface mixtures (SMs) with conventional and high reclaimed asphalt pavement (HRAP) contents through full-scale accelerated testing under incremental loading conditions while accounting for the environmental aging effect. HRAP SMs were designed in this study, marking the initial application of Virginia Department of Transportation (VDOT) BMD special provisions, with attempts to incorporate 45% and even 60% RAP. Results showed that all BMD HRAP mixtures exhibited higher rut depths compared to the control mixture, which can be attributed to the inclusion of high binder contents aimed at enhancing cracking resistance. The asphalt pavement analyzer (APA) rut test and the stress sweep rutting tests were performed on mixtures sampled during production. Correlation analysis revealed significant and strong positive correlations between accelerated pavement testing (APT) and the multilevel laboratory rutting performance tests considered in this study. Finally, while acknowledging the limitations and all the assumptions considered in this study, the correlation analysis recommended refining the VDOT BMD APA rut depth threshold by lowering the current limit of 8 mm to 7 mm to ensure good performing mixtures from a rutting point of view.