Investigating the Potential of Limestone and Calcined Clay as a Substitute for Fly Ash in Strain-Hardening Cementitious Composites (SHCC)

This study focuses on the feasibility of replacing fly ash with limestone and calcined clay in strain-hardening cementitious composites (SHCC). Three types of composites were considered: a reference one containing fly ash and the other containing two distinct calcined clays (moderate and high metakaolin content) as supplementary cementitious materials (SCM). Mixtures utilized portland cement (PC) with clinker factors of 0.4 and 0.3, reinforced with 2 vol.% high-density polyethylene (HDPE) fibers. At first, the R3 bound water test was carried out to explicitly assess the reactivity of fly ash and the two calcined clays. Subsequently, the compressive and direct tensile behavior of the SHCCs after 28 days of curing age was evaluated. The results revealed that the SHCCs incorporating calcined clays outperformed their counterpart in terms of compressive strength, tensile strength, and ultimate strain, owing to their high pozzolanic activities, and physical properties, particularly their distinct morphologies. Crack analysis conducted through digital image correlation (DIC) highlighted that the SHCCs with calcined clays established a stronger fiber/matrix interface. In conclusion, this research provides valuable insights into the design of ductile SHCC with novel limestone calcined clay cement (LC3), for enhanced sustainability and cost-effectiveness.