Bitumen has been used in different forms and with various properties in pavement as a binder material. Meanwhile, the properties of soil-rubber mixtures (SRM) have been extensively examined for applications in geotechnical and highway engineering. These applications range from serving as a lightweight fill material, subgrade layers in pavement, and foundation materials for geotechnical seismic isolation (GSI). However, a research gap exists in understanding the effect of the interaction between bitumen and rubber granules on their mechanical properties under a range of confining pressures. In this paper, a series of unconfined compressive strength (UCS) and monotonic triaxial tests were conducted. The results show that a bitumen content as low as 3% of the total mass can significantly increase the shear strength and cohesion of SRM and reduce the deformability. Moreover, the increase in the elastic modulus due to a 3-5% bitumen content is notably less than the reduction obtained from 25% to 45% rubber replacement, which is favourable for GSI applications. The shear strength and elastic modulus in gravel-based mixtures were found to be more sensitive to changes in rubber and bitumen content compared to sandbased mixtures. Conversely, the effect of confining pressure was more pronounced in sandy soil than in gravelly soil.
