Strength and bonding properties of polymer-modified hardened gypsum plaster

The strength elongation at fracture and bonding power of hardened products consisting of inorganic binders are important properties for their use in t he construction industry. A means of specifically influencing these propert ies in the case of hardened gypsum plaster is the addition of polymers. The action of various polymers with regard to hardening behaviour; mechanical properties and bonding were investigated. To this end, different proportion s of selected polymers were added to the gypsum binder suspension before th e production of normal test specimens. The bonding strength was determined by means of pull-out tests with embedded wood chips. It was shown that the influence of synthetic resins on the hydration of the gypsum binder can alr eady give an indication of the strength development of the hardened gypsum plaster. In particular synthetic resin dispersions or redispersion powders containing polyvinyl acetate can increase the strength of hardened gypsum p laster. Synthetic-resin-modified hardened gypsum plaster exhibits markedly better bonding. At higher synthetic resin/gypsum binder ratios, good bondin g strength was achieved even to difficult bonding partners.