Stiffening effect of filler on asphalt mastic composite: A new insight based on nearest surface function. (15th August 2022) - Jia, Yanshun
Highlights: A novel methodological framework analyzing critical property of asphalt mastic was developed. A novel method to calculate filler critical volume fraction was established. Transformation from volume-based into number-based distribution functions for filler particles was conducted. Nearest surface distance of filler particles in asphalt mastic was estimated through nearest surface functions. Filler critical volume fraction of asphalt mastic under different temperatures was computed. Abstract: This study aims to provide a new insight into the reinforcement effect of filler on stiffness of asphalt mastic through the probability theory, nearest surface function and micromechanics. To implement the consideration of microphysical mechanisms in the stiffening behavior of asphalt mastic composite, a general methodological framework was developed. A new method to calculate the filler's critical volume fraction (CVF) in asphalt mastic was constructed through the volume fraction of penetrable transition zone (PTZ) acting as a link. Particle size distribution (PSD) of filler was tested by a laser particle size analyzer. Asphalt mastics were fabricated with different filler concentrations. Distributions of filler particles in these mastics were tested by a scanning electron microscope. Complex stiffness moduli of asphalt binder and mastics were tested by a dynamic shear rheometer. Nearest surface distance (NSD) of filler particles in asphalt mastics was analyzed by nearest surface functions. Filler's CVF in asphalt mastics was calculated through the constructed method. Results show that the shifted Rosin-Rammler distribution function allows to describe the PSD of filler with a high accuracy. Void nearest-surface exclusion probability of filler particles allows to represent the volume fraction of free asphalt in asphalt mastic. The larger the filler volume fraction, the higher the proportion of NSD making particles intercontact. A filler particle with larger radius has more likely to contact with other filler particles, and thus large particles tend to dominate the interparticle interaction in asphalt mastic. The mean NSD of filler particles decreases with increasing the filler volume fraction. The volume fraction of PTZ has an increased first and decreased afterwards trend with the filler volume fraction. The filler's CVF decreases with the temperature increases. The constructed method is capable of determining the filler's CVF in asphalt mastic.