Mechanical Behavior of Polymer-Modified Bituminous Mastics. I: Experimental Approach

Abstract

The dynamic shear rheometer was used to investigate the effect of polyphosphoric acid (PPA) and styrene-butadiene-styrene (SBS) modification on the rheological and mechanical behavior of asphalt binder and asphalt mastic. In this research, three SBS contents (2%, 4%, and 6%) and three PPA contents (0.5%, 1%, and 2% by weight of neat asphalt binder) were used. Also, two volume fractions (18% and 35%) of silica filler were selected to fabricate asphalt mastic samples. In total, 1 neat asphalt binder, 6 modified asphalt samples, and 12 modified asphalt mastics were investigated. By using storage and loss moduli data of all samples in a frequency range between 0.1 and 100 Hz at various temperatures between −25°C and 22°C, the Cole-Cole and black space diagrams were plotted and analyzed. The results clearly show that the linear viscoelastic behavior of asphalt mastic is directly related to asphalt binder because of the identical forms of the Cole-Cole curve. An optical microscope was also used to see filler particle distribution in the bitumen structure. The stiffening phenomenon for a volume fraction of 35% was observed in comparison with a volume fraction of 18%, consistent with other previous research work. Adding PPA causes extra stiffening related to formation of the strong structure of PPA between filler particles.