Evaluation of the adhesion characteristics of material composition for polyphosphoric acid and SBS modified bitumen based on surface free energy theory

Abstract

Styrene-butadiene-styrene (SBS) modified bitumen is widely applied to the construction of high-grade pavement because of its good pavement properties. However, with the rising price of SBS polymer, SBS modified bitumen is more expensive. By adding the cheap modifier polyphosphoric acid (PPA) to bitumen and compounding with SBS, the production price of SBS modified bitumen is obviously reduced, and the miscibility between SBS and bitumen is promoted. In this study, the effect of base bitumen type, PPA type and raw materials content on the adhesion performance of polyphosphoric acid compounded SBS (PPA/SBS) modified bitumen was evaluated quantitatively using the contact angle test and surface free energy method. Three different bituminous materials, two types of PPA, SBS, stabilizer, compatibilizer and dibutyl phthalate (DBP) were used as raw materials to prepare PPA/SBS modified bitumen. The results indicate that PPA improves the adhesion of PPA/SBS modified bitumen, but with an increase in PPA content above a certain value, the cohesion work, adhesion work and compatibility ratio of PPA/SBS modified bitumen decrease gradually and the peeling work increases gradually. In the blending process of PPA and SBS, changes in adhesion performance depend mainly on the base bitumen type, PPA type and raw material content. Using SK 90# base bitumen; 105% PPA; and PPA, DBP, extraction oil, and SBS contents of 0.5%, 1%, 1.5%, and 3.5%, respectively, the water damage resistance of PPA/SBS modified bitumen is considerably improved.