Date of Award

2016

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy in Civil Engineering (PhD)

Administrative Home Department

Department of Civil and Environmental Engineering

Advisor 1

Zhanping You

Advisor 2

Qingli Dai

Committee Member 1

Patricia Heiden

Committee Member 2

Jianping Dong

Abstract

The main objectives of this dissertation are to build the Molecular Dynamics (MD) model for the asphalt binders with three components, asphaltenes, aromatics and saturates, and analyze the properties of the asphalt models to discover the interactions and mechanisms of asphalt-aggregate and asphalt-modifier. The contributions of this dissertation are summarized as follows: (1) the Amber Cornell Extension Force Field (ACEFF) was assigned to each component, and most of the parameters of the force field were obtained from the General Amber Force Field (GAFF). Electrostatic Potential (ESP) charges were assigned to each atom with the NWChem calculation; (2) the modified asphalt model with the multi-layer graphite nanoplatelets (xGNP) was generated by the MD method to analyze the effect of the modifier on the asphalt binder model; (3) the aged components of the asphalt model were proposed, and the analysis of moisture susceptibility of asphalt-aggregate by the MD method; (4) the interaction or diffusion of the asphalt binder on aggregates was also realized by the MD method.

The MD simulations and laboratory test evaluations show that (1) the MD asphalt model with ACEFF and ESP charges has a better prediction for the different properties than the reference model; (2) The primary aging products in the asphalt binder contain ketones, carboxylic acids and anhydrides. The difference in adhesion was observed between aggregate-asphalt and aggregate-water interfaces; (3) the addition of xGNP nanoplatelets in the asphalt model increased the density, viscosity and thermal conductivity. The same trend was observed in the experimental data. A better observation of these properties was found in the xGNP modified asphalt model compared to the base asphalt model; (4) Different moduli of the asphalt binder models had a trend similar to that of the laboratory test results; (5) The asphalt started to diffuse when the activation energy was reached, and the contact angle and area of the asphalt-aggregate interface changed. Therefore, the findings or conclusions in this dissertation have a good guidance for improving the performance of asphalt binders. Most importantly, this dissertation provides a promising way to analyze and develop the material and its properties.

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