Evaluation of binder and mixture performance in crumb rubber asphalt modified with Sasobit

The accumulation of waste tires and their environmental impact is a serious global issue. Incorporating Crumb Rubber (CR) into asphalt mixtures allows this waste to be recycled while improving pavement performance, but it also increases production temperatures, energy use, and emissions. Warm Mix Asphalt (WMA) additives can mitigate this drawback, enabling more sustainable mixtures. This study presents laboratory investigation of the rheological properties and mechanical performance of CR–modified asphalt binder and mixtures obtained by wet process and containing Sasobit as a WMA additive. The bitumen investigation employed penetration, softening point, viscosity, and dynamic shear rheometer tests. Results showed that CR increased binder stiffness, as evidenced by reduced penetration and higher softening point, while Sasobit further contributed to lowering penetration at low temperatures but also reduced viscosity at high temperatures, thus improving workability. The formulation with 15 % CR and 3 % Sasobit (15 %CR–3 %S) emerged as the optimal compromise, achieving a high-temperature Performance Grade (PG 82) without excessive stiffness. The dynamic (complex) modulus and fatigue resistance at different temperatures and load frequencies of the 15 %CR CR–3 %S modified asphalt mixture, intended for use as the wearing course of road pavements, were evaluated through 4-point bending tests. Moreover, dynamic creep tests were conducted to assess its rutting resistance. Compared with the unmodified asphalt mixture, the modified one generally exhibited a higher complex modulus, improved fatigue resistance, and enhanced rutting resistance. These results indicate that combining CR with Sasobit enhances binder rheology and asphalt mixture performance while supporting lower-temperature production, contributing to the development of more sustainable asphalt pavements. • Binder–mixture tests clarify Sasobit effects on CR-modified asphalt performance. • 15 % crumb rubber + 3 % Sasobit gives the best workability–stiffness balance. • Sasobit lowers viscosity and enables reduced mixing and compaction temperatures. • CR–Sasobit binder reaches high-temperature grade PG 82 without excessive stiffness. • Modified mixtures show higher modulus, better rutting resistance, and good fatigue.