Investigation of the conventional and rheological properties of bitumen with SIS and CR modification

Hot mix asphalts require modification to resist increasing traffic loads and detrimental effects on the environment. Because polymer types of materials that are used in the modifications are expensive, it is necessary to investigate the use of economically viable additive materials as alternatives in terms of sustainability. In this study, the usability of crumb rubber (CR) and Striren-Isopren-Stiren (SIS) as alternative additives to Styrene-Butadiene-Styrene (SBS), which has been used recently, was investigated. It was aimed to create a design that was more viable economically by reducing the ratio of polymer modification in mixtures without sacrificing performance. Additionally, the utilization of SIS and CR additives as alternative additives to SBS modification, which is the most common additive material of today, was evaluated on a wide scale. Thus, it was attempted to improve the high and low-temperature characteristics of bituminous binders, hence, bituminous mixtures. In the study, pure bitumen was modified with CR and SIS additives both separately and together in the same mixture. In this way, 14 specimens with different contents were prepared. The efficiency of the additives was extensively evaluated by conducting softening point, penetration, dynamic shear rheometer (DSR), rotational viscometer, and bending beam rheometer tests on both pure and aged binders. These testing methods aim to determine high and low-temperature performances, resistance to aging, workability, and flexibility characteristics of the binders. According to the results of the study, it was determined that using 2% SIS and 7% CR by the weight of the bitumen demonstrated both more economic and superior performance compared to binders with only SIS or CR. Furthermore, it was determined that binders with two modifiers preserved their flexible characteristics after aging in a better way only compared to binders with SIS or CR