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    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
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      <title>Research in Progress (RIP)</title>
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      <title>A Screening Tool for Assessment of Moisture-Induced Damage of Asphalt Mixes Containing RAP Based on Molecular Dynamics Simulation</title>
      <link>https://rip.trb.org/View/2291283</link>
      <description><![CDATA[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. Using Bell’s model, the pulling velocity v=v_0 exp(f x_b⁄k_b  T), where x_b is the distance between the equilibrium states and the transition state, and v_0=ω_0 x_b exp⁡((-E_b)⁄k_b  T), where f is the external pulling force, x_b is the distance between the equilibrium state and the transition state, k_b is Boltzmann’s constant, T is temperature,  ω_0 is the natural vibration frequency, and E_b is the adhesion energy, will be quantified. The adhesive strength obtained from the MD simulations will be compared with the direct tensile strength determined in the laboratory using a pneumatic adhesion tensile testing instrument. 
The following tasks will be performed to meet the project goals: Task 1: Determine adhesion energy following the procedure described in Gao, P. et al. (Appl. Surf. Sci. 2022, 577, 151930) for standard AAA-1 type binder. Use the asphalt binder model described in Li, D. D. and Greenfield, M. L. (Fuel 2014, 115, 347–356) with SiO2 and CaCO3; 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; Task 6: Develop a MS Excel-based interactive spreadsheet based on results from Task 5 that can be used by designers as a tool for evaluating aggregate-binder compatibility in presence of rejuvenators and resistance to moisture-induced damage of asphalt mixes.
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      <pubDate>Wed, 15 Nov 2023 17:19:44 GMT</pubDate>
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