Developing high-strength dry-cast pastes by incorporating carbonatable chlorellestadite

A water-insoluble mineral, chlorellestadite (CE, Ca₁₀(SiO₄)₃(SO₄)₃Cl₂), would be formed in the preheater coatings of cement kilns when using chlorine-containing plastics as alternative fuels. This work investigated the viability of employing CE as an SCM to enhance the utilization of chlorine-containing fuels in cement-making. Substituting 20 wt% CE in dry-cast pastes (CE20), which were prepared by compaction method with zero workability, exhibited decreased compressive strength after 1d carbonation curing because of reduced cement content. However, carbonating CE introduced secondary gypsum into the binder system, leading to more ettringite formed in pores after water curing, aligning with thermodynamic modeling predictions. Its formation refined the pore structure, leading to 28d strength of CE20 (93.4 MPa) exceeding the OPC reference by 21.1 %. These findings underscored the potential of using CE as an SCM in dry-cast non-structural concrete and the advantages of carbonating minerals to generate secondary gypsum and ettringite for enhancing concrete properties.