Effect of rubber particles on fracture properties and microstructure of matrix for PDCC

Non-biodegradable rubber waste from tyres can be employed for the making of pseudo-ductile cementitious composites (PDCC) which requires a matrix of low toughness. In the present study, compressive strength and fracture toughness are measured for cementitious mortar containing small volume of sand, and with or without rubber particles. Also micro-hardness testing, mercury intrusion porosimetry and scanning electron microscopy are performed. According to the test results, the incorporation of 10%∼11% rubber particles with average size of 0.4mm or 0.2mm by volume decreases the compressive strength by 40%∼60% and the fracture toughness by 10%∼40% which makes preparation of PDCC easier. These can be explained by the presence of cracks at the interface between rubber particle and matrix, as well as the increased porosity and specifically the increased content of large capillary pores in the cementitious composites with rubber particles which is considered as solid air-entraining agent. Moreover, there is a more significant increase in the content of capillary pores for composites with small size rubber particles, explaining the lower strength and toughness when these particles are employed.