Feasibility of using calcined clays and reclaimed coal ashes in binary and ternary cementitious systems

Abstract

This study evaluates the feasibility of using three different calcined clays (CCs) to partially replace ordinary Portland cement (OPC) in concretes. Furthermore, the best performing CC was investigated in conjunction with the addition of reclaimed fly ash (RFA) or reclaimed ground bottom ash (GBA) to partially replace OPC. OPC replacement levels by mass considered in the present study for both binary (i.e., OPC + CCs) and ternary (i.e., OPC + CC + GBA or RFA) cementitious systems were 10, 20, and 30 %. It was shown that, relative to the control mixture (CO), the utilization of CCs can significantly improve properties of the hardened concrete, at the cost of significantly reducing the workability of fresh concrete mixtures. Conversely, the incorporation of coal ashes to form ternary system produced concretes with superior hardened properties (relative to CO) while partially mitigating workability loss. Overall, both binary and ternary systems can produce concretes with significantly higher strength and surface resistivity. Additionally, characteristics of CCs that could be used as rapid indicators to predict their performance as supplementary cementitious materials (SCMs) in concrete were identified by coupling materials characterization techniques and concrete test results.