Recycled Aggregate Concrete - An Investigative Study

Abstract

Australia generates approximately 43,777,000 tonnes of waste annually, in which 38% are classified as construction and demolition (C&D) waste. Recycled aggregate (RA), a construction material derived from C&D waste, has a comparatively higher water absorption rate, lower strength and modulus than natural aggregate (NA). These properties of RA have lead to their limited and low grade applications, mainly in road subbases and as fill materials. As the construction industry is actively seeking for more sustainable materials, the demands of utilising RA in high grade applications such as, as concrete aggregates are increasing. This paper summarises experimental results on workability, compressive strength, indirect tensile strength and modulus of elasticity of recycled aggregate concrete (RAC) produced using air-dry aggregates with a constant water to cement ratio of 0.45 and 25%, 50%, 75% and 100% replacement of NA by RA. The recycled aggregate samples used in this study are collected from a centralised recycling plant in Brisbane, Australia. Preliminary result shows that the effect of air-dry aggregate on concrete workability is within an acceptable range and can be rectified by adjusting mixing time.