Characterization of Sustainable Asphalt Binders Modified with Styrene–Isoprene–Styrene (SIS) and Processed Oil

The current study aims to evaluate the viscosity and rheological properties of PG 64-22 modified with Styrene–Isoprene–Styrene (SIS) and Processed Oil (PO) to enhance asphalt binder properties. Performance properties were measured at high, intermediate, and low temperatures. PG 64-22 was blended with SIS and Processed Oil at three levels (5%, 10%, and 15% by weight of binder) and two concentrations (6% and 12% by weight of binder), respectively. Modified binders underwent two short and long artificial aging processes, through the spinning of the thin film in an RTFO oven and a pressure aging vessel (PAV). The Superpave binder evaluations were carried out using a rotational viscometer (RV), dynamic shear rheometer (DSR), and bending beam rheometer (BBR). According to the findings of the research, the addition of SIS caused higher values of viscosity, but when co-modified with processed oil, there was a substantial decrease in viscosity values. As a result, workability was improved. (1) It was observed that a greater reduction in viscosity was achieved when the processed oil was present at a higher concentration at 135 °C compared to a lower concentration. (2) The study showed that the incorporation of processed oil led to a reduction in rutting performance of the asphalt binder. However, the addition of SIS resulted in a notable enhancement of rutting resistance. (3) The role of processed oil as co-modifier at concentrations of 6% and 12% caused significant decreases in G*sin δ, based on the susceptibility of asphalt molecules to accept oil molecules in their network links. (4) The extracted measurements from the BBR tests indicated that modification with SIS and PO improved the low-temperature cracking resistance significantly. Comparison of asphalt binders modified with 6% and 12% PO and the same SIS content showed significant changes in modification with 12% PO rather than 6%.