RHEOLOGICAL PROPERTIES OF ROAD BITUMEN BINDERS MODIFIED WITH SBS POLYMER AND POLYPHOSPHORIC ACID

A commonly used method to improve the viscoelastic properties of road bitumens is polymer modification with styrene-butadiene-styrene (SBS). New binder modifiers are being searched for to provide a technically and economically justified alternative. A recent method of modification, which has been in use for over 15 years (mainly in the U.S.), is based on addition of polyphosphoric acid (PPA). The effect of modification with polyphosphoric acid is similar to that of oxidation, i.e. it increases the binder stiffness yet without compromising its low-temperature performance. The effect of modification with polyphosphoric acid has not been so far comprehensively tested in Poland. According to various reports from research projects carried out in different countries improvement of binder properties and durability of asphalt mixtures largely depends on the type of pure bitumen used. This paper describes the effect of PPA modifier on the rheological properties of a bitumen obtained from a Polish refinery.