A fire-resistant gypsum panel comprises: a gypsum core layer comprising set gypsum and a high temperature sag-resistant material including mineral wool in an amount between 0.2% and 3.0% by weight of gypsum.

Disclosed are an organic binder-based coating; a composite gypsum board containing face and back cover sheets, an outside surface of the back cover sheet bearing the coating; and a method of preparing composite board where the back cover sheet contains the coating on its outer surface. The coating is formed from a composition comprising an alkaline silicate, a solid filler, and optionally, a borate. An enhancing layer can also be applied to the back cover sheet.

A waterproofed gypsum board and associated method are provided, featuring the use of a mixture of magnesium oxide and a gypsum crystal modifier for improving the resistance to sagging of the waterproofed gypsum board, in particular, in moist and warm climatic conditions.

The invention concerns an anti-sagging additive for producing shaped gypsum articles. The additive is boron-free and comprises L-tartaric acid and/or L-tartrates and a pH-enhancing compound.

Vinyl ester/ethylene copolymer aqueous dispersions containing an anionic polyacrylamide, at least one polyvinyl alcohol, and optionally a non-ionic surfactant, are useful in cementitious compositions as polymer additives.

Disclosed are an organic binder-based coating; a composite gypsum board containing face and back cover sheets, an outside surface of the back cover sheet bearing the coating; and a method of preparing composite board where the back cover sheet contains the coating on its outer surface. The coating is formed from a composition comprising an alkaline silicate, a solid filler, and optionally, a borate. An enhancing layer can also be applied to the back cover sheet.

The present invention provides a composition, a gypsum board and their preparation method and the use of ascorbic acid as an anti-sagging additive in a gypsum board. Said gypsum board comprises set gypsum prepared from the composition; while said composition comprises hemi-hydrate gypsum, water and a compound comprising ##STR00001##
group and no carboxylate groups. The set gypsum prepared from the said composition shows better anti-sagging or deformation resisting property. The gypsum board of the present invention is hardly distorted and has stronger stability even in the condition of high humidity, thus improve the quality of the gypsum board to meet the demands of the customer.

Vinyl ester/ethylene copolymer aqueous dispersions containing an anionic polyacrylamide, at least one polyvinyl alcohol, and optionally a non-ionic surfactant, are useful in cementitious compositions as polymer additives.

A gypsum board according to the invention comprises calcium sulphate dihydrate; Tartaric acid in an amount in the range of 0.01 to 0.1% w based on the weight of calcium sulphate hemihydrate; A fluidizer in an amount of 1.0 to 10.0 kg/m.sup.3; Starch in an amount of 3.0 to 12.0 kg/m.sup.3.

The present invention concerns an additive for construction chemical compositions, in particular mortar and cement compositions. The additive comprises at least one amide or ester of a sugar acid and at least one water-soluble comb polymer which contains, on the main chain, acid functions and side chains having ether functions. The additive is useful for retarding the hardening of a construction chemical composition.