Using low-grade calcined clay to develop low-carbon and lightweight strain-hardening cement composites

Abstract

The paper reports the use of low-grade calcined clay (LCC), a waste clay from construction and excavation works, to produce low-carbon and lightweight strain-hardening cement composites (SHCC). The influence of LCC content (20, 40 and 60% by mass) on the hydration, microstructure, strength, ductility, shrinkage and embodied carbon of SHCC has been investigated. Pozzolanic reaction between LCC and cement hydration products has been observed, which results in significant pore refinement at 20% and 40% cement replacement. The density of SHCC containing LCC was only around 1600 kg/m3. The compressive strength, tensile strain, and tensile strength of SHCC mixtures containing 20% LCC were improved by 3.21%, 22.10%, and 32.28%, respectively. A continued increase in LCC substitution caused a decrease in the strength by the agglomeration of LCC and insufficient calcium hydroxide supply. Furthermore, a significant reduction in embodied carbon was achieved by replacing cement with LCC. Overall, this study shows that low-grade calcined clay has a high potential in producing low-carbon and lightweight SHCC.