Water-resistant gypsum products

A process for preparing a set, water-resistant gypsum product comprising providing a mixture of water, gypsum, at least about 0.15 wt. % polyvinyl alcohol and at least about 3 wt. % wax-asphalt emulsion, and forming and setting said mixture into said gypsum product, wherein the total amount of said polyvinyl alcohol and said wax-asphalt emulsion present in the mixture is such that the water-resistant properties of said gypsum product are greater than a gypsum product prepared from a like gypsum mixture which contains one of said polyvinyl alcohol or said wax-asphalt emulsion in an amount the same as the figure of said total amount.

A composition, capable of being set by water into a water-resistant gypsum product, comprising at least about 87 wt. % and no greater than about 96 wt. % gypsum, about 0.15 to about 0.4 wt. % of polyvinyl which is about 97 to 100% hydrolyzed polyvinyl acetate and about 3 to about 5 wt. % of wax-asphalt emulsion, wherein the total amount of said polyvinyl alcohol and said wax-asphalt emulsion present in the composition is such that the water-resistant properties of said gypsum product are greater than a gypsum product prepared from a like gypsum composition which contains one of said polyvinyl alcohol or said wax-asphalt emulsion in an amount the same as the figure of said total amount.