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Gypsum paste was subjected to the temperatures up to 1000 °C and its microstructure was investigated by SEM microscopy. The volume and mass changes were also measured and the bulk density, porosity and residual strength were determined. After heating to the 1000 °C the structure of paste changed substantially, as can be seen in the micrographs. The structure of heated material is denser and the anhydrite crystals are bigger. The volume of the samples decreased more than 50%. The bulk density increased by 20%, whil...

The paper emphasizes the ecological restoration (renaturation) of the natural conditions of a saline soil, which was previously under long term melioration. The soil is a Salinic Pelic Alluvic Sodosol with relict gleization, covering an Alkali soil (according to SRTS-2012). The site is located in Moldova Tableland, where Tma is 584.6?C and Pma is 9.5 mm. The depth of the groundwater table is about 1.80 m, with frequent seasonal fluctuations and weak-moderate mineralization. The soil had a polyphasic evolution, bot...

The properties of materials obtained during the thermal treatment of gypsum depend on structural defects in the multiphase gypsum-anhydrite system. Analysis of the crystal structures of gypsum (CaSO4·2H2O), bassanite (CaSO4·0,5H2O), ?-anhydrite (?-CaSO4) and natural anhydrite (?-CaSO4) allowed us to identify a common structural motif in each of these structures. This is an irregular hexagon formed by chains of ?Ca?SO4?Ca?SO4?. During successive thermal transformation of gypsum into anhydrite, this structural motif...