Improving the Durability Properties of Self-Consolidating Concrete made with Recycled Concrete Aggregates using Blended Cements

Abstract

The paper evaluates the durability properties of Self-Consolidating Concrete (SCC) containing fine and coarse recycled concrete aggregates. The SCC mixtures were made with 0%, 25%, 50%, 75% and 100% substitution of Fine Natural Aggregates (FNA) with Fine Recycled Concrete Aggregates (FRCA) whereas Coarse Natural aggregates (CNA) were partially substituted (50%) with Coarse Recycled Concrete Aggregates (CRCA). Ordinary Portland Cement (OPC) was blended with 30% of Fly Ash (FA) which is further substituted with 10% of Metakaolin (MK). The durability parameters of SCC mixtures were evaluated using tests such as, Initial Surface Absorption Test (ISAT), Water Penetrability Test, Rapid Chloride Penetrability Test (RCPT), and Capillary Suction Test (CST). The Compressive strength test and Ultrasonic Pulse Velocity (UPV) test was also conducted on SCC mixtures. The durability and compressive strength properties of the SCC mixtures were found to deteriorate with the replacement of both CNA and FNA. At 120 days of curing, an increase of the order of 17.5%, 18.7%, 7.1% and 26.7% was observed in the results obtained in ISAT, RCPT, CST and Water Penetrability Test respectively with the substitution of FRCA with FNA and CRCA with CNA. However, the introduction of MK in the concrete matrix proved very effective as the values of ISAT, RCPT, CST and Water Penetrability Tests were observed at par with the control mix even with 75% FRCA and 50% CRCA content. In case of compressive strength, 9.3% drop was observed with 100% FRCA and 50% CRCA content. However, the presence of MK has been found to compensate this to 4.5% only. Moreover, all SCC mixtures with CRCA and FRCA and MK can be classified in the excellent category on the basis of their UPV values.