Evaluation indices of asphalt–filler interaction ability and the filler critical volume fraction based on the complex modulus

The asphalt–filler interaction plays a significant role in the performances of asphalt mastics and mixtures, and the asphalt–filler interaction ability could be evaluated by the rheological properties. In this paper, two kinds of matrix asphalt binders and six kinds of fillers were selected to prepare asphalt mastic with different filler volume fractions, and the dynamic shear rheological properties of asphalt mastics were measured and analysed. The filler critical volume fraction which is the transition point from “diluted region” to “concentrated region” for asphalt mastic was defined and determined according to the variation of asphalt mastic’s complex modulus with filler volume fractions. In the “diluted region”, the asphalt–filler interaction plays a dominant role in the increasing of complex modulus. However, the interaction between filler particles plays a dominant role in the “concentrated region”. Then, the complex modulus coefficient ΔG*, the Einstein coefficient KE and the coefficient K−B−G* were applied to evaluate the asphalt–filler interaction ability in the range of the filler critical volume fraction. It indicated that the three evaluation indices had good consistency for characterising the asphalt–filler interaction ability, but the coefficient K−B−G* had the best sensitivity. So the coefficient K−B−G* can significantly distinguish the interaction ability between asphalt binder and different fillers.