An experimental study on the shear behaviour of recycled concrete aggregate incorporating recycled tyre waste

Very limited research has been conducted to examine the shear behaviour of blended recycled waste materials using the large direct shear testing apparatus. In this study, a series of large-scale direct shear test (LDST) was undertaken to evaluate the effect of different sizes and different amounts of recycled tyre waste on the shear strength properties of recycled concrete aggregate (RCA) mixed with crumb rubber as pavement base/subbase application. The results of LDST indicated that RCA mixed with two different sizes (i.e., fine and coarse rubber) and three different percentages (i.e., 0.5%, 1% and 2%) of crumb rubber satisfied the shear strength requirements for use in pavement base/subbase applications. The introduction of both fine and coarse crumb rubber led to an increase in the apparent cohesion of RCA/rubber blends. However, beyond 0.5%, increasing the content of crumb rubber resulted in a decrease in the apparent cohesion. Based on the results of the laboratory testing undertaken in this research, a rational and useful model was proposed to estimate the shear strength parameters of RCA incorporating crumb rubber.