Compression properties and micro-mechanisms of rubber-sand particle mixtures considering grain breakage

The waste materials of scrap tires are becoming more prevalent in geotechnical engineering. While adding scrap tires particles into sand particles as a filling material can reduce the stockpiles of scrap tires and minimize the environmental pollution. Therefore, investigating the effect of scrap tires-sand particle mixtures on compression properties is in urgent demand. In this study, the effect of the rubber particle content and vertical stress on the actual density, void ratio, coefficient of compressibility, modulus of compression, rebound and grain breakage is investigated systematically by a serious of laboratory tests. The test results reveal that when rubber content RV exceeds 50% (or less than 50%), the three-stage change trend of void ratio is proposed: accelerating reduction, deceleration stage and slow reduction (or accelerating reduction, slow reduction and stable stage). A region where the actual density is lower than the control density is given under different vertical stress and RV. In accordance with the coefficient of compressibility, the rubber-sand mixtures used in this paper is categorized into three groups: (1) Low compressive materials (RV = 0-10%); (2) Medium compressive materials (RV = 20-30%); (3) High compressible materials (RV > 50%). The addition of rubber particles to sand particles generates a significant reduction in modulus of compression, and the modulus of compression at the same rage of vertical stress decays exponentially with increasing RV. In addition, the plastic strain of specimens is greater than the elastic strain, and the gap between elastic strain and plastic strain is increasing with the increase of RV. A good linear relationship is derived between grain breakage Br and RV. Obviously, the particle breakage decreases with the increase of RV at different vertical stress levels. Based on the analysis of SEM, three force transmission ways with different RV are proposed to describe the compression micro-mechanic of rubber-sand particle mixtures.