Performance of rubber mortars containing silica coated rubber

This paper investigates the influence of silica coated rubber on the performance of rubber mortars. A classical Stöber sol-gel method is applied to produce a layer of silica coating on rubber particles, which is used to partially replace the fine aggregates in concrete. The effects of the surface-modified rubber particles on the flowability, mechanical strength, capillary water absorption rate, and microstructure of mortars are examined. The results show that the silica coating on the rubber particles reduces the contact angle between the rubber particles from 120° to 103° (i.e., by 17°) and changes the hydrophobic properties from strong hydrophobicity to weak hydrophobicity. The mechanical strengths of mortars are significantly improved by the incorporation of surface-modified rubber particles, i.e., from 41.60% to 44.86% (compressive strength) and from 7.80% to 26.28% (flexural strength). In addition, the incorporation of surface modified rubber particles increases the density of the mortar’s microstructure and enhances the interfaces with its surrounding pastes.