Investigation of the effects of using styrene-butadiene-styrene in conjunction with gilsonite on the mechanical properties of hot mix asphalts

In this study, the effect of the combined use of styrene-butadiene-styrene (SBS) and the American Gilsonite (AG) modifications on rheological properties of bituminous binders and mechanical properties of hot mix asphalts was investigated. Suitable binder performance level for Sanliurfa province was determined to be PG 76-10 according to the Superpave method. Firstly, the modified bitumen (PG 76-16) with an appropriate performance level for Şanlıurfa was obtained using SBS and American Gilsonite only. Then, the SBS content in SBS-modified bitumens was reduced, and American Gilsonite at different portions was added instead. Thus, at least 3 different modified bitumens with SBS + American Gilsonite with an appropriate level of performance for Şanlıurfa was obtained. Sample mixtures were prepared with 2 binders containing a single additive (5% SBS ve 18% AG) and at least 3 binders containing two different additives (4% SBS + 6% AG, 3% SBS + 10% AG ve 2% SBS + 13% AG), which have the same performance level. Marshall stability and flow, resistance to moisture damage, indirect tensile stiffness modulus, indirect tensile fatigue and dynamic creep tests were applied to hot mix asphalt samples prepared in the design bitumen content. Thus, the effect of the use of American Gilsonite in conjunction with SBS on stability, moisture damage, stiffness, permanent deformation was tried to determine. As a result of the experiments in aforementioned study, improvement of the rheological properties of the binder, positive effect on the mix of all additives stability, resistance to moisture damage, stiffness, fatigue life and resistance to permanent deformation with the use of additive was determined. The most effective additives as 18% AG and 3% SBS + 10% AG on Marshall stability, Marshall quotient, tensile strength, flow number and the creep modulus, the most effective additives as 18% AG, 2% SBS + 13% AG and 3% SBS + 10% AG on stifness and fatigue life, the most effective additives as 5% SBS, 2% SBS + 13% AG and 3% SBS + 10% AG on the resistance to moisture damage, the use of 5% SBS as the additive which increased the elasticity of mixture most were determined. When considering all the results, the conclusion was reached that instead of the use of alone SBS or AG, the combined use of SBS and AG is more beneficial.