Experimental investigation on the mechanical and damping properties of rubber-sand-concrete prepared with recycled waste tires for aseismic isolation layer

Waste tires pose a serious potential threat to environment. Recycling and reusing of waste tires are becoming more important and prevalent. Meanwhile, the aseismic design of underground tunnels requires a material with a low strength able of dissipating the ground motion energy. Therefore, a new type of rubber-sand-concrete (RSC), which is composed of a specific formula of rubber particles, sand, and cement, is proposed. The ingredients proportions in the RSC formula were investigated considering the seismic design demand for underground tunnels. The effects of rubber content (RM), cement content (CM), and rubber particle size (RPS) on the mechanical and damping properties such as density, Poisson's ratio, elastic modulus, compressive and tensile strengths, energy dissipation ability, dynamic shear modulus as well as the damping ratio were discussed. Based on current research, the RM and CM have a notable influence on the mechanical and damping properties, while the influence of RPS is insignificant within a specific range of 0.075-2 mm. When the RM is higher than 30%, or the CM lower than 50%, or the RPS lower than 1 mm in the selected formula scheme, the phase for which the RSC can withstand more deformation before failure is observed. The elastic modulus, compressive and tensile strengths decay exponentially with the RM increase. In addition, the RSC morphological characteristics and energy dissipation performance with different formula schemes subjected to dynamic impacts are presented. The dynamic shear modulus and damping ratio correlation are detailed. Based on the SEM analysis, the influential mechanisms of different ingredients proportions on the RSC properties are discussed.