Experimental investigation on the influence of interfacial effects of limestone and fly ash filler particles in asphalt binder on mastic aging behaviors

Abstract

The incorporation of mineral filler has significant influence on the rheological response of asphalt binders over oxidative aging. This study focuses on understanding the physicochemical interaction of filler particles (i.e., fly ash and limestone) to asphalt binders and how fillers affect oxidative aging of binder by using Atomic Force Microscopy (AFM) and Fourier Transform Infrared (FTIR). The microstructural and chemical characteristics regarding base asphalt as well as different asphalt adsorbed films of fly ash and limestone asphalt mastics were obtained before and after aging process via AFM and FTIR, respectively. The results show that significant differences in terms of surface morphology were obtained for binders with different fillers. The typical “bee-like” structure was not found but instead “flake-like” or round shape dispersed phases appeared on the surface various asphalt adsorbed samples. As approaching the filler surface, the size and number of these dispersed phases changed under the asphalt -filler interaction effect. The infrared peaks of carbonyl and sulfoxide bands are used to evaluate the extent of oxidative aging. Compared to the base asphalt, the oxidation resistance of binder was improved by adding fly ash and limestone filler. Moreover, the IC=O and IS=O aging indexes of each asphalt adsorbed film of fly ash asphalt mastics were lower than that of corresponding sample of limestone asphalt mastic.