Mechanical performance and water resistance of a carbonated hemihydrate gypsum and slaked lime composite

In order to improve the strength and water resistance of hemihydrate gypsum, slaked lime was incorporated and a carbon dioxide curing technique was used. First, hemihydrate gypsum, slaked lime, and water were mixed at different proportions. The mixture was pressed into block samples by a compression machine at a pressure of 3 MPa and placed a curing kettle full of CO2 at a pressure of 0.3 MPa. The results of mechanical performance tests show that when the ratio of gypsum to lime is 7 to 3 and the water to solid ratio is 0.2, the compressive strength of the sample cured under CO2 can reach 29.1 MPa and the softening coefficient is 1.05. The results of microscopic characterization show that the main constituents are dihydrate gypsum and calcium carbonate. These observations will provide guidance to the application of carbonated hemihydrate gypsum and slaked lime composite.