Effects of di̇fferent natural asphalts on the properti̇es of bi̇tumen and hot mi̇x asphalts

In this dissertation study, the effects of using different natural asphalts and styrene-butadiene-styrene (SBS) as a binder modifier were investigated. Three different natural asphalts (Trinidad Lake Asphalt (TLA), Iranian Gilsonite and American Gilsonite) and SBS were used as additive in bitumen modification. Binder and mixture design were done according to Superpave method. Bituminous binders were short- and long-term aged in accordance with rolling thin film oven test (RTFOT) and pressure ageing vessel (PAV) procedures. Rotational viscosimeter (RV), dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests were done on bituminous binders. Marshall stability and flow, moisture-induced damage, indirect tensile stiffness modulus, indirect tensile fatigue and wheel tracking tests were done on the hot mix asphalt samples. Results of binder tests showed that addition of 10.0% American Gilsonite (MB10%AG), 9.5% Iranian Gilsonite (MB9.5%IG), 60% Trinidad lake asphalt (MB60%TLA) and 3.8% SBS (MB3.8%SBS) to pure bitumen (PG 58-34) achieved the desired performance level (PG 70-34). Experiments conducted on mixtures showed that mixtures prepared with MB60%TLA had the highest stiffness, stability, tensile strength and resistance to fatigue and permanent deformation. On the other hand, mixtures prepared with MB9.5%IG and MB3.8%SBS were observed to have highest resistance to moisture induced damage. Keywords: Hot mix asphalt, Modification, Natural asphalt, Styrene-butadiene-styrene.