Preparation of specific gypsum with advanced hardness and bending strength by a novel In-situ Loading-Hydration Process

An interesting approach named as “In-situ Loading-Hydration Process” is proposed and demonstrated to develop a new type of compact gypsum product with load-bearing ability, benefited from excellent hardness and bending strength. In detail, bassanite (CaSO4·0.5H2O) is press-formed in a mold and in-situ hydrated into gypsum (CaSO4·2H2O) under the control of loading-pressure. The maximum hardness of 1.47 GPa and bending strength of 17.8 MPa are achieved at the loading pressures of 50 and 20 MPa, respectively. These outstanding mechanical properties of the processed gypsums are mainly attributed to the low-level porosities and interlocking crystal microstructures.