Shear behaviour of crushed concrete and bricks

Demolition waste materials mainly consist of concrete and bricks and arise from the demolition of existing structures and buildings. Environmental and economical reasons make their recycling necessary, but to date, their use is curtailed due to the lack of research in determining their properties. This paper reports on the efforts to understand the behavioural characteristics of three types of recycled material to determine their potential for engineering fill applications. For this purpose, their physical and mechanical characteristics were extensively investigated. Two types of crushed concrete, one obtained straight after demolition and the other processed to industry specifications, and one type of crushed brick were tested. An extensive large-scale shear box test regime was employed to determine the shear strength behaviour of the materials. The influence of the normal stress on the peak friction angle, the shear stress– horizontal displacement relationship and horizontal displacement– vertical displacement behaviour of the materials are discussed in this paper. The results showed that the behaviour of the three recycled materials during shear testing was similar to the behaviour exhibited by natural granular materials from literature. In conclusion, the shear box test results have shown that the specific demolition waste products exhibit considerable shear strength and can be utilised in construction as low-level engineering fill.