Experimental studies on utilization of coarse and finer fractions of recycled concrete aggregates in self compacting concrete mixes

Abstract This experimental study deals with utilization of Coarse Recycled Concrete Aggregate (CRCA) and Fine Recycled Concrete Aggregates (FRCA) in Self compacting concrete (SCC) mixes. The concrete mix is designed for target strength of 40 MPa as per “Modified Nan-su Method”, with Fly Ash as mineral admixture. Four mixes are considered in the study viz., Control Mix (CM) with natural aggregates, 20% CRCA, 20% FRCA and both at 20% replacement levels. The slump flow and T500 time, V-funnel time, L-box height ratio, GTM stability test are conducted to evaluate the fresh properties of SCC mixes. The slump flow test result of the SCC mix containing 20% CRCA and FRCA, fails to satisfy the EFNARC (European Federation of National Associations Representing for Concrete) acceptance criteria marginally. However, results of T500 time, V-Funnel time, L-box height ratio, GTM screen stability test of all the four mixes are found to be within the specified limits. The tests on hardened properties are conducted to assess the cube compressive strength at 3, 7 and 28 days and split tensile strength of cylinders at 28 days. The hardened properties of SCC mixes containing recycled concrete aggregates (RCA) are found to be slightly higher than CM. Based on test results with respect to fresh and hardened properties and with focus on concrete waste utilization, SCC with 20% (CRCA+FRCA) is considered as the preferred mix combination. The durability tests such as sulphate and acid attack are conducted for this mix. The compressive strength is found to reduce by about 11% and 40%, after thirty days of immersion in Na 2 SO 4 and H 2 SO 4 solutions respectively.