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

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 modem 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 Al3+ 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. (c) 2006 Elsevier B.V. All rights reserved.