AN INVESTIGATION OF SHEAR FRICTION - IN R.C.A. CONCRETE

Abstract

The use of recycled concrete aggregate is considered one of the viable means of producing a more environmentally friendly concrete. Using crushed concrete as coarse and fine aggregate reduces the use of natural resources and reduces the use of landfills. Sources of concrete for crushing can be obtained from various sources such as demolished buildings and reject concrete from ready mix plants. The suitability of the use of RCA as aggregate for structural concrete needs to bejustified using research on different aspects of its behaviour. The shear behaviour of concrete depends on various factors including a phenomenon referred to as aggregate interlock. This report investigates the shear friction behavior of different grades of RCA concrete and also benchmark the same with comparable concrete made using natural coarse aggregates. The RCA as well as the natural coarse aggregate particles have been used in the saturated surface dry (SSD) moisture state. Shear friction behavior has been investigated with the help of pushoff specimens for two concrete grades representative of a normal and a high-strength concrete mixture. Equivalent mixture proportions have been used for the RCA concrete and three RCA replacement levels by weight of the natural coarse aggregates were considered: nil, 50% and 100%. For each concrete type, grade and RCA replacement level the following three combinations of transverse reinforcement crossing the shear plane were considered: 3 bars of 3mm diameter, 3bars of 6mm diameter and 3 bars of 8mm diameter. The measured shear strengths have been compared with predictions from relevant AC! and PCI codes as well as predictions from selected empirical shear friction models available in the literature.