Optimizing crystallization processes in desulfurized gypsum using zinc oxide for superior construction gypsum

This study investigates the relationship between crystal characteristics and performance enhancement in construction gypsum through zinc oxide modification of desulfurized gypsum. Systematic experiments demonstrated that ZnO addition effectively controlled crystal formation and improved material properties across multiple parameters. The incorporation of 0.6 % ZnO facilitated complete conversion to α-hemihydrate at temperatures between 160 and 200 °C, with optimal crystallization observed at 180 °C. Microstructural analysis revealed that ZnO modification promoted the formation of interlocking needle-like crystals with lengths of 20–30 μm and widths of 1–2 μm after 7 days of hydration. The modified gypsum exhibited significantly enhanced performance characteristics, including reduced water demand (66.8 % vs 71.2 % for control), moderate setting times (initial 8.2 min, final 13.5 min), and superior mechanical properties. The progressive strength development showed continuous improvement over time, with 7-day flexural and compressive strengths reaching 4.8 MPa and 21.5 MPa, respectively. The modified crystal structure demonstrated improved packing density and reduced porosity (35.2 % compared to 38.5 % in unmodified samples), contributing to enhanced material performance. These findings provide valuable insights for industrial-scale production of high-performance construction materials from desulfurization byproducts.