Preparation and performances of SBS compound modified asphalt mixture by acidification and vulcanization

Polyphosphoric acid (PPA) was used to improve the performances of styrene–butadienestyrene (SBS) modified (SM) asphalt mixture further and decline the SBS content, however the negative effect of PPA on the performances of SM asphalt mixture is still unclear. The major purpose of this paper is to indicate the negative effect and provide an efficient way to solve the problem. In this paper, SM asphalt, SBS/PPA-modified asphalt (SPMA), SBS/PPA/sulfur-modified asphalt (SPSMA) were prepared, the physical properties were studied and the morphology was investigated by using scanning electron microscope (SEM). The mixtures of base asphalt (BA), SM asphalt, SPMA, SPSMA were designed and prepared in the light of Superpave mixing design method and Phoenix specifications. Universal testing machine (UTM) system was used to investigate the effect of SBS, PPA, sulfur on the properties of BA mixture. It was found that PPA declined the crack, fatigue resistance and moisture susceptibility of SM asphalt mixture and the problem can be solved well by vulcanization, the morphology change of SBS from coarse particle to threadlike one after vulcanization prompted the swelling of SBS in asphalt. Therefore SBS compound modified asphalt pavement material with better performances and lower cost can be prepared by taking advantage of acidification and vulcanization.