UTC 2022 Funding - Cycle 1 Research Projects

Project No.: CY1-LTU-02
Title: A Screening Tool for Assessment of Moisture-Induced Damage of Asphalt Mixes Containing RAP Based on Molecular Dynamics Simulation
Performing Institution: Louisiana Tech University
Principal Investigator: Andrew Peters and Nazimuddin Wasiuddin, Louisiana Tech University
Start and Anticipated Completion Dates: 10/1/2023-9/30/2024
Abstract: Infiltration of moisture into asphalt mixes leads to diminished performance, shortened lifespan, and unforeseen failures, thereby reducing the environmental and economic sustainability of road networks. Although the damage mechanism for moisture-induced damage was identified in the 1970s, the underlying fundamentals are not well understood. Also, most of the moisture-induced damage evaluation techniques rely on empirical test methods. In this project, the research team seeks to develop a screening tool for the assessment of moisture-induced damage potential of asphalt mixes containing reclaimed asphalt pavement (RAP). Molecular dynamics (MD) simulation, a widely accepted physics-based numerical simulation technique, will be used to examine the compatibility between asphalt binders and aggregates, including RAP. Because rejuvenators are used frequently in asphalt mixes containing RAP, particularly with increased RAP contents, rejuvenators will be included in the MD simulations. Adhesive interactions between asphalt binder and aggregate, in the presence of moisture, will be used as an indicator of compatibility or resistance to moisture-induced damage. Because of the limited budget and timeline, existing asphalt, aggregate, and rejuvenator molecules will be used in the MD simulations. Atomistic molecular dynamics will be used to simulate the binder and aggregate interfaces and determine the interaction energies and adhesive strengths between the binder and the aggregate. Bell’s model will be used to quantify the adhesion energy. The adhesive strength obtained from the MD simulations will be compared with the direct tensile strength determined in the laboratory using pneumatic adhesion tensile tests. The following tasks will be performed to meet the project goals: Task 1: determine adhesion energy following the procedure described in the literature; Task 2: determine the adhesion energy as a function of water concentration; Task 3: calculate the adhesion energy as a function of water concentration for selected additives or rejuvenators; Task 4: conduct laboratory tests to determine direct tensile strengths; Task 5: compare adhesion energy obtained from the MD simulations with the direct tensile strength results from Task 4, and Task 6: conduct a parametric study involving different parameters and develop an excel-based interactive spreadsheet that can be used by designers as a tool for evaluating aggregatebinder compatibility in presence of rejuvenators and resistance to moisture-induced damage of asphalt mixes. This project is expected to provide guidelines for improving the compatibility between asphalt binder and aggregate, with and without rejuvenators, in the presence of moisture. The Excel-based spreadsheet will be used to determine the optimum rejuvenator amount and binder-aggregate compatibility using the results from the MD simulations.
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