CHARACTERIZATION OF STYRENE-BUTADIENE-STYRENE POLYMER-MODIFIED BITUMENS - COMPARISON OF CONVENTIONAL METHODS AND DYNAMIC-MECHANICAL ANALYSES

Rheological properties of styrene-butadiene-styrene polymer (SBS) modi fied bitumens were studied using conventional test methods (penetratio n, softening point, kinematic viscosity and Fraass breaking point) and dynamic mechanical analysis (DMA). The study indicated that SBS modif ication improved the viscoelastic properties of bitumens, which can be demonstrated using DMA but not conventional methods. Significantly im proved properties of binders included increased dynamic mechanical mod uli and decreased phase angle at high temperatures, as well as reduced complex modulus and increased phase angle at low temperatures. SBS mo dification also caused reductions in glass transition temperature, Fra ass breaking point, and temperature susceptibility. The degree of impr ovement was observed to be influenced by bitumen source/grade and poly mer content/structure. Comparison showed that certain relationships ex ist between parameters obtained using conventional methods and DMA, su ch as between penetration and complex modulus, kinematic viscosity and complex viscosity, and Fraass breaking point and glass transition tem perature. However, the main conclusion of the study is that convention al test parameters such as penetration and softening point are not sui table for characterization of rheological properties of SBS modified b itumens.