Relation between the reactivity and surface area of gypsum

Concrete/Glass Construction and Demolition Waste (CDW) Synergies in Ternary Eco-Cement-Paste Mineralogy

The study described sought further understanding of the synergies in a mix of CDW pozzolans, containing (calcareous and siliceous) concrete and glass waste, used to prepare ternary eco-cement paste bearing 7% of the binary blend at concrete/glass ratios of 2:1 and 1:2. The mineralogical phases in the 2-day, 28-day, and 90-day cement matrices were identified and monitored using XRF, XRD-Rietveld, SEM-EDX, FT-IR, and NMR. The findings showed that changes in the reaction kinetics in the ternary blended pastes relative to OPC pastes depended on the nature of the recycled concrete and the glass content. Adding the binary mix bearing calcareous concrete (at a ratio of 2:1) favoured ettringite, portlandite, and amorphous phase formation, whilst the blends with siliceous concrete favoured C-S-H gel formation. Monocarboaluminate was detected in the 90-day siliceous concrete and glass pastes in amounts similar to those found in the reference OPC paste.

Red gypsum utilization and acidic wastewater treatment based on metal self-enrichment process

The massive accumulation of red gypsum has brought great harm to human and environment. In order to achieve low-cost and high-benefit resource utilization of red gypsum, a method of metal self-enrichment during the cycle and transformation of red gypsum was proposed. The carbon dioxide and ammonia water react with red gypsum to manufacture ammonium sulfate and solid phase products. And solid phase products neutralize pickling wastewater to produce metal-enriched red gypsum for the next cycle. After the cycle, solid phase product with one circulation (containing 39.45% Fe and 7.37% Ca) and two circulation (containing 45.79% Fe, 4.75% Ca) could be obtained, which can be used as the proportioning of metallurgical sinter. The self-enrichment process not only realizes the comprehensive utilization of red gypsum, but also solves the treatment of acidic wastewater.