Performance of Recycled Aggregate Concrete Incorporating Copper Slag at Elevated Temperature

Effective and economic utilization of waste materials produced from different construction and industry sectors is a big challenge for the engineers and researchers in the recent decade due to its disposal and environmental issue. In this context, the present research work utilizes recycled concrete aggregate and copper slag as a substitution of natural coarse and fine aggregates to produce waste based and environmentally friendly concrete. This experimental study aims to analyse the impact of using copper slag as a replacement of fine aggregate on the characteristics of recycled aggregate concrete exposed at elevated temperature. For this, total seven number of mixes and 315 number of samples were prepared in two series of mixes. Natural coarse aggregates are replaced by recycled coarse aggregate of varying proportions (0%, 33%, 66% and 100%) in the first series, whereas copper slag is utilized to substitute as fine aggregate up to 60% with increments of 20% in the second series to examine the different properties of various concrete mixtures containing 33% recycled coarse aggregate. The mixtures were designed for M30 grade concrete with control mix proportion of 1:2.20:3.053 as per IS code of practice. Properties like compressive strength, split tensile strength, flexural strength, mass loss and ultra-sonic pulse velocity of various concrete mixtures were evaluated before and after exposure of different temperatures (i.e., 30 degrees C, 200 degrees C, 400 degrees C, 600 degrees C and 800 degrees C) and the values were compared with that of control concrete. The study revealed that, although the strength properties of all the mixes reduced with the increased temperature, the residual performance of recycled aggregate concrete is found satisfactory with the addition of copper slag up to 40% as a replacement of fine aggregate and comparable with the control concrete. The optimum performance is attained by the addition of 20% copper slag, i.e. up to 25% higher mechanical strength than the control mix at elevated temperature up to 800 degrees C. From the microstructural analysis, it was confirmed that by incorporating up to 40% copper slag as a replacement for fine aggregate, the development of voids is minimum in comparison with control concrete which escalated the residual strength properties. Thus, using RCA and CS as waste materials could decrease the quantity of natural resources used in the building sectors as well as reduce the amount of waste disposal.