Strength and microstructure analysis of sustainable self-compacting concrete with fly ash, silica fume, and recycled minerals

Abstract

Self-Compacting Concrete (SCC) is often made with natural aggregates and a portion of single or binary admixtures in place of Ordinary Portland Cement (OPC). The use of Recycled Coarse Aggregates (RCA) derived from demolition and rubble wastes may also be beneficial and may provide a number of benefits, including maintaining ecological balance, providing cost-effective constructions, lowering CO2 emissions, reducing excessive resource consumption, and producing concrete for sustainable development. In order to partially replace the OPC and Natural Coarse Aggregates (NCA) for the production of M−30 grade SCC, the current work explores and uses a combination of mineral admixtures viz., Fly Ash (FA) + Silica Fume (SF), and RCA, respectively. The effect of inclusion of these admixtures in both separately (FA and SF) and combination (FA + SF) with and without RCA content on the fresh properties, compressive strength and microstructure characteristics (XRD and SEM) of all the SCC mixtures for the durations of 28, 120, 270 and 540 days, are evaluated. It is concluded that the compressive strength of different SCCs rises in the range of 1.26–19.10 % when using different type of admixture(s) or their combination, but the strength of various SCCs decreases in the range of 2.14–5.08 %, when using RCA content in the SCC mixtures. Also, concrete containing either FA, SF or FA + SF content are beneficially used in the SCCs but the mechanical characteristics of SCC mixtures are negatively impacted by RCA content.