Study of Gypsum Samples with Additions of Mineral Particles

The DSC method revealed endothermic effects (–613.9 J/g) during gypsum dihydrate heating associated with the heat absorption during the release of crystalline hydrate water in the range of 100–250°C during the heating process. Mass losses during water evaporation were determined by TGA and amount of up to 20%. The thermal conductivity coefficient of gypsum samples is 0.288 W/m K. The influence of mineral additives—glass spheres, wollastonite, and chopped basalt fiber—on changes in the properties of gypsum samples at curing times of 2 h and 1, 3, 7, and 14 days was studied. An addition of glass spheres up to 10 wt % reduces gypsum strength by 10–13% and density, by 16%, additive up to 20 wt % reduces strength by two times and density by 36–40%, and additive up to 50 wt % reduces strength by from five to six times and density by 80–85%, with the thermal conductivity coefficient decreasing to 0.236 W/m K. An addition of wollastonite 10–20 wt % increases the strength of gypsum samples by 13–16%, and addition of 50 wt % reduces the strength by two times. An addition of 0.5–1.5 wt % chopped basalt fibers increases strength by 10–16%, as well as the strength gain rate. Additions of wollastonite and basalt fibers practically do not change the density of gypsum samples, but increase the thermal conductivity coefficient to 0.320–0.373 W/m K.