Investigation of the effects of polyurethane additive on the traditional and rheological properties of CR modified bitumen

It has become inevitable to modify the bitumen with various additives in order to improve the properties of bituminous mixtures. The most common additive used is styrene-butadiene-styrene (SBS). The fact that SBS additive is expensive keeps the search for alternative additives constantly. Ground rubber (CR) obtained from waste vehicle tires is used in bitumen modification due to its economic and ecological benefits. CR modification does not perform as well as SBS in terms of some rheological properties. Therefore, generally, CR additive is used together with various polymers to achieve the desired performance with lower polymer consumption. In this study, the effectiveness of the CR modified binder was increased by the addition of polyurethane (PU). Addition of 4% PU to 8% CR modification was compared with SBS and CR modification by determining its traditional and rheological properties. Softening point, viscosity, dynamic shear rheometer (DSR), beam bending rheometer (BBR) and storage stability tests were applied to binders. As a result, it was determined that the use of PU together with CR significantly improved the properties of the CR modification, offered better high and low temperature properties than the SBS modification, and was more stable in terms of storage.