Cross-scale analysis of asphalt binder tensile fracture using molecular dynamics simulation

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The tensile failure behavior of asphalt binder is crucial for longevity and durability of asphalt concrete, which is one of most common infrastructure materials. This study provides a cross-scale approach to investigate tensile fracture of asphalt binder using MD simulations. First, two asphalt models for asphaltene-doped and saturate-doped binders were constructed at nanoscale. Tensile simulations were then conducted to observe the evolution of nanovoids and changes in voids surface area. Using tensile strength values at various temperatures and strain rates, the master curve of tensile strength was established based on time-temperature superposition. Results show that cohesive cracking in asphalt binders begins with nanovoids, which rapidly evolve into larger cavities and form thinning filamentation structures, eventually resulting in a complete crack. Locations with lower concentrations of polar components are more likely to initiate nanovoids. After complete fracture, voids surface area of asphaltene-doped binder is larger than that of saturate-doped binder. Increasing the proportion of asphaltene enhances tensile strength of asphalt binders. As expected, tensile strength increases with strain rate but decreases with temperature The time-temperature superposition method is shown to be effective in obtaining macroscale tensile strengths from MD simulations that are comparable to experimental measurements. This study presents an effective simulation method to obtain cross-scale parameters, providing new insights into crack initiation and propagation in asphalt binders.