Friction and fracture characteristics of engineered crumb-rubber concrete at microscopic lengthscale

Using small-scale depth-sensing techniques, we shed light on the determinants of friction and hardness in engineered crumb rubber reinforced concrete with applications into railway sleeper ties. Microscopic scratch tests were carried out to assess the hardness, friction and fracture behavior of concrete specimens reinforced with crumb rubber inclusions. Optical microscopy and scanning
electron microscopy are utilized to identify the micro-constituents. The partial replacement of aggregates with crumb rubber particle leads to an increase in the friction coecient and the fracture toughness and a slight decrease in strength properties. Our research suggests that the crumb rubber particle specific area may play a role in dictating the levels of enhancement in friction coecient. In addition, improper bonding at the cement/rubber interface is shown to result in poor strength characteristics. Furthermore, crumb
rubber particles contribute to a higher durability as evidenced by sustained high values of the friction coecient even in presence of surface lubrication with water or oil. Overall our study highlights the beneficial role of crumb rubber on the friction and fracture behavior while emphasizing the need for more research into the eect of specific surface area and interface bonding.