Potential of desulfurized gypsum as a sulfate alternative in preparing solid waste-based limestone calcined clay cement (LC3) and its effects on early properties

Desulfurized gypsum (DG) presents significant challenges in recycling with the rapid development of industrialization. To explore the feasibility of DG as a sulfate source in producing limestone calcined clay cement (LC3), this study investigates the differences between LC3 samples containing DG and those containing natural gypsum (NG) in terms of hydration, workability and mechanical properties. Results indicate that at the same addition of gypsum, DG samples exhibited lower promotion in rheological parameters and weaker retardation in setting time relative to NG samples. For strength development, the optimal content of NG samples was 3 wt%, whereas no such similarity was observed in DG samples. Furthermore, the mixture incorporating higher amounts of sulfate exhibited a lower aluminate peak and slower consumption of capillary water. Although differences in the sulfate source had no effect on the phase species of LC3, the amount of ettringite increased with the addition of gypsum (especially NG), while exhibiting a further growing trend as the curing age prolonged. This study is expected to develop novel LC3 binder formulations by promoting the utilization of DG, thereby achieving sustainable development.