INFLUENCE OF STYRENE-BUTADIENE-STYRENE POLYMER MODIFICATION ON BITUMEN VISCOSITY

Effects of polymer content/structure and bitumen type on viscosity cha racteristics of styrene-butadiene-styrene (SBS) polymer modified bitum ens were investigated. The study indicated that SBS polymers were not inert additives and increases in kinematic and dynamic viscosities of the modified bitumens were not directly proportional to polymer conten t; a marked viscosity increase was observed when the polymer content i ncreased from 3 to 6% by weight of the blend. Modification with a suff iciently high polymer content also increased the degree of non-Newtoni an behaviour of the bitumens. The base bitumens and modified bitumens containing 3% SBS were observed to be essentially shear rate independe nt, while those containing 6 or 9% SBS displayed shear-thinning behavi our. Compared to the modified bitumens with linear SBS, the modified b itumens with branched SBS demonstrated a higher degree of shear-thinni ng behaviour. These effects were dependent on ranges of shear rate and temperature. The increased degree of non-Newtonian behaviour was obse rved to influence the correlations between kinematic and dynamic visco sities. (C) 1997 Elsevier Science Ltd.