The influences of gypsum water-proofing additive on gypsum crystal growth

Abstract The gypsum water-proofing additives were composed of organic emulsion that were emulsified by polyvinyl alcohol and stearic acid and saline water-proofing additive made of alunite, carboxylic acid sodium, aluminium sulfate, etc. Using modern testing instrument, such as SEM, EPS, the influences of gypsum water-proofing additives on the crystal growth of gypsum products and its water-proof mechanism were analyzed from the perspective of the crystal changing of gypsum after adding gypsum water-proofing additive. Such results show that organic emulsion can be adsorbed selectively on the gypsum crystal surface, inhibiting the crystal growth along axis c . Besides, anion RCOO − , cations Na + and Al 3+ in saline water-proofing additive can be adsorbed selectively to crystal section (111) to coordinate, slowing down the growth speed along axis c , which could balance the speed in all directions and turn the crystal into a short hexahedron pole.