Characterization of RCAs and their concrete using simple test methods

Abstract

From a sustainability point of view, the use of recycled concrete aggregate (RCA) in concretes is of great interest in the present day. The original virgin concrete from which RCA is obtained determines the properties of the RCA, and it also controls the durability of recycled aggregate concretes (RACs) produced. In this study, the performance of three sources of RCAs with different absorption, obtained from crushed concrete pavement and stockpiles, were evaluated using various mechanical, thermal and non-destructive durability test methods. Suitability of RCA for cold climates was evaluated using a test method for the resistance of unconfined coarse aggregate to freezing and thawing (CSA A23.2-24A). The mechanical properties of the RACs were assessed with the compressive strength test. Non-destructive durability tests on the RACs included surface and bulk electrical resistivity, ultrasonic pulse velocity (UPV), and volume of permeable voids (ASTM C642, boil test). The effect of RCAs on the thermal conductivity of concrete was also evaluated. All of the measured properties of RACs were compared with a concrete mix containing natural virgin aggregate. Correlations between the absorption of aggregates and measured properties were also established. The test results provide an overall understanding of the feasibility of using different sourced RCAs in concretes.