Research on degradation mechanisms of recycled building gypsum

In order to provide a solid theoretical foundation for the efficient reuse of waste gypsum, the research on the degradation mechanisms of recycled gypsum mechanical performance was carried out in this paper. The recycled gypsum was prepared with natural gypsum ores in the laboratory and three rational comparative methods were proposed through constraining the conditions: the preparation process, the particle size distribution and the water/gypsum ratio. The results showed that the recycled dihydrate gypsum was much easier to grind than the natural gypsum ores, resulting in deteriorated particle size distribution, large specific surface area and void fraction, poor sphericity, which remarkably increased the water requirement. The increase in porosity and larger pore size due to excessive water evaporation was the determining factor leading to a significant decrease in the strength of the recycled gypsum. However, the short columnar shape crystals seemly would only have a slight disadvantageous on the flexural strength. Moreover, the crystal morphological characteristics of dihydrate gypsum had a decisive influence on the sphericity of recycled hemihydrate particles. (C) 2018 Elsevier Ltd. All rights reserved.