In general, the present invention is directed to a method of making a gypsum board. The method comprises: applying a phosphorus containing compound to a first gypsum composition to provide a phosphorus modified gypsum composition; calcining the phosphorus modified gypsum composition to provide a calcined gypsum composition; preparing a gypsum slurry by combining water and the calcined gypsum composition; depositing the gypsum slurry on a first facing material; providing a second facing material on the gypsum slurry; and allowing the calcined gypsum to convert to calcium sulfate dihydrate.

A method of conditioning stucco comprises the steps of supplying a quantity of stucco particles to a reaction vessel, the stucco particles comprising calcium sulphate hemihydrate and/or calcium sulphate anhydrite, as well as calcium sulphate dihydrate; and conditioning the stucco particles at a temperature of at least 100? C. and a humidity of at least 70%. During the step of conditioning the stucco particles, the bulk density of the stucco particles within the reaction vessel is at least 1 g/cm.sup.3.

Disclosed is a composite gypsum board comprising a board core and a concentrated layer of substantial thickness (e.g., at least about 0.02 inches). The concentrated layer includes a higher weight percentage of an enhancing additive than the hoard core. The board core has a thickness greater than the thickness of the concentrated layer and forms the bulk of the board volume. The concentrated layer has a higher density (e.g., at least about 1.1 times greater) than the density of the board core. Also disclosed is a method of preparing a composite gypsum board.

Disclosed is a composite gypsum board comprising a board core and a concentrated layer of substantial thickness (e.g., at least about 0.02 inches). The concentrated layer includes a higher weight percentage of an enhancing additive than the board core. The board core has a thickness greater than the thickness of the concentrated layer and forms the bulk of the board volume. The concentrated layer has a higher density (e.g., at least about 1.1 times greater) than the density of the board core. Also disclosed is a method of preparing a composite gypsum board.

The present disclosure relates more particularly to calcium sulfate-based slurries useful, for example, in making gypsum boards for building construction, as well as methods for using them, e.g., to make gypsum boards, in one aspect, the present disclosure provides a calcium sulfate slurry composition comprising calcium sulfate present substantially in the form of one or more hydrates, the calcium sulfate being present in an amount in the range of 70-99.8 wt % on a dry basis, calculated as stucco; and a cationic starch present in an amount of 0.10-10 wt % of the amount of calcium sulfate as stucco on a dry basis, the cationic starch being substituted with amine and/or ammonium groups and having a % N value in the range of 0.10 wt. % to 2 wt %, and an RVA viscosity value of at least 100 cP at 65 C. and 16 wt %; and water, in an amount sufficient to form a slurry. The disclosure also provides gypsum-based materials useful as building materials, e.g., for use as building boards in construction of walls and ceilings of buildings.

The Invention is related to increasing of early strength and final strengths of cements classified under EN and ASTM as Portland or CEM cements and also related to all clinker employing cements and to any kinds which employ calcium sulphates for set optimization and is for composing of new cements by only assessing new methods for production and is for composing of new cements by only assessing new methods to formation and inclusion of calcium sulphate resources which are used for set optimization. A new calcium sulphate resource is obtained by employing lower heats and this input is arranged to different dehydration levels at which they can be most efficient for the selected use. These different dehydration levels are called intermediate phases of dehydrate or hemihydrates or called as monohydrate.