Research on surface morphology characteristics and micro-damage mechanism of asphalt mastic based on charge transfer principle

Abstract

Asphalt mastic damage is a major element influencing the mechanical qualities of the asphalt mixture. Based on electrochemistry theory, the idea of charge transfer of moisture between asphalt-asphalt and asphalt-mineral powder is proposed in this study to explore the damage mechanism of asphalt mastic under the operation of freeze–thaw cycles.On this basis, the damage mechanism of asphalt mastic was analyzed at multiple scales using relevant experimental means (Scanning electron microscopy-Energy dispersion spectrum(SEM-EDS) experiment, Fourier Transform Infrared(FT-IR) experiment and Atomic Force Microscope(AFM) experiment). FT-IR and AFM experiments results showed that: Water molecules in asphalt mastic might compete for asphaltene electrons in the asphalt mastic, causing the carboxyl dimer formed between asphaltenes to be disrupted. This causes asphaltene dispersion and a reduction in asphaltene concentration. Asphalt colloid structure changes from gel to sol, causing asphalt mastic degradation. Furthermore, freeze–thaw cycles accelerate the damage. On the other hand, the results of FT-IR and SEM-EDS experiments showed that: Freeze-thaw processes in asphalt mastics can also result in varying pore sizes and higher carbon concentration. Water molecules can create structural water on the subsurface of mineral powder crystals as well as physical water on the surface of mineral powder. This affects the adsorption of structural asphalt on the subsurface of the mineral powder crystals, resulting in the dissociation of the adsorbed asphalt from the mineral powder crystals' surface. The results of the study have some theoretical value to further explore the damage mechanism of asphalt mastic.