Rheological characterization of styrene-butadiene-styrene copolymer modified bitumens

The rheological properties of styrene-butadiene-styrene copolymer (SBS) modified bitumens were studied. The modified binders were prepared using a laboratory mixer. Five types of bitumen from four sources were mixed with two SBS polymers at different polymer content levels. The rheological properties of the modified binders were characterized using dynamic mechanical analysis over wide ranges of temperatures and frequencies. It was found that the addition of the SBS polymers increased the binder elasticity at high temperatures and improved the binder flexibility at low temperatures. The temperature susceptibility of bitumens was also reduced by SBS modification; however, this property cannot be evaluated with a single-valued parameter. The degree of modification with respect to the binder rheology varied with temperature and frequency, and was dependent on the bitumen source/grade and the polymer concentration and structure. (C) 1997 Elsevier Science Ltd.