EFFECT OF SURFACE ACTIVE SUBSTANCE CONCENTRATION ON THE PROPERTIES OF FOAMED AND NON-FOAMED GYPSUM

Foamed gypsum was prepared by direct foaming. Properties of foamed and non-foamed gypsum were investigated using plaster suspensions containing surface active substances (SAS). Since SAS have amphiphilic properties, their solutions are prone to foaming. The combination of foaming and the hydration of calcium sulphate hemihydrate (CaSO4.1/2H2O) led to fast solidification, resulting in strong, porous bodies. Bulk density, compressive strength and the pore size varied markedly depending on both the quantity of SAS and water/plaster weight ratio. Bulk density of the foamed gypsum ranged from 0.20 to 0.58 g/cm3 and the pore size reached 50 micron to 1.3 mm, depending on the concentration of the surfactant. The compressive strength of the foamed gypsum and the non-foamed one increased with increasing bulk density. The dried non-foamed gypsum showed high compressive strengths up to 12 MPa.