Gypsum panels, sheathing systems, and methods of making and using the same are provided. A gypsum panel includes a gypsum core associated with a first fiberglass mat having a continuous barrier coating, the coating penetrating a portion of the first fiberglass mat opposite the gypsum core, wherein gypsum penetrates a remaining fibrous portion of the first fiberglass mat such that voids in the first fiberglass mat are substantially eliminated. A building sheathing system includes at least two gypsum panels and a seaming component to provide a seam at an interface between the gypsum panels.

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.

Techniques of forming a foamed insulation material from gypsum waste are disclosed herein. One example technique includes mechanically comminuting the gypsum waste from an original size into particles of gypsum at a target size smaller than the original size and mixing the particles of the gypsum with a binder to form a mixture of particles and binder. The binder is configured to bind the particles of gypsum upon hydration. The example technique can further include performing air entrainment on the mixture until a foam is formed from the mixture having the particles of gypsum and binder. The foam has water that causes the binder to bind the particles of gypsum. The example technique can then include removing moisture from the mixture with the formed foam to form a foamed insulation material from the particles of gypsum.

Aspects of the invention include a method of producing a cement material comprising step of: first reacting a calcium-bearing starting material with a first acid to produce an aqueous first calcium salt; second reacting the aqueous first calcium salt with a second acid to produce a solid second calcium salt; wherein the second acid is different from the first acid and the second calcium salt is different from the first calcium salt; and thermally treating the second calcium salt to produce a first cement material. Preferably, but not necessarily, during the second reacting step, reaction between the first calcium salt and the second acid regenerates the first acid.

A method for continuously forming gypsum-based panels of high fixing strength comprises the steps of: •forming a mixture comprising stucco, non-pregelatinized migratory starch, glass fibre, fluidizer and water; •casting the mixture in a continuous band; •maintaining the band under conditions sufficient for the stucco to form an interlocking matrix of set gypsum; •cutting the band to form one or more wet panel precursors; and •drying the wet panel precursor to form one or more gypsum-based panels. •The weight ratio of water to stucco in the mixture is less than 0.7; •the stucco is present in the mixture in an amount of over 60 wt % relative to the total solids content of the mixture; •the starch is present in the mixture in an amount of over 3 wt % relative to the stucco; •the glass fibre is present in the mixture in an amount of over 1 wt % relative to the stucco; •the fluidizer is present in the mixture in an amount of at least 0.1 wt % relative to the stucco; and the density of the gypsum-based panel is greater than 700 kg/m.

Beads of materials such as activated alumina, zeolite and silica gel, are used as chloride salt absorbers. The beads are mixed with high-salt gypsum. After mixing for a short time, the mixtures are dried, and the beads and the powder are separated by using a sieve or other physical separation device resulting in a low-salt gypsum which can be used as a gypsum source to make gypsum wallboard.

A method of recovering desalinated activated alumina (AA) beads from a composition including salt laden (high salt absorbed) activated alumna (AA) beads and free anions and free cations, comprising the step of electrodialysis of the composition to reduce salt content of the activated alumina (AA) beads to produce a stream comprising the desalinated activated alumina (AA) beads.

An embodiment according to the present invention provides a dental gypsum powder including a hemihydrate gypsum and a water-reducing agent, wherein the mass ratio of the water-reducing agent to the hemihydrate gypsum is 0.1 to 1%, the content of particles having a particle diameter of 10 μm or less is 15 to 35 volume %, the content of particles having a particle diameter of 20 μm or less is 40 to 55 volume %, and the content of particles having a particle diameter of 30 μm or less is 55 to 75 volume %.

An embodiment according to the present invention provides a dental gypsum powder including a hemihydrate gypsum and a water-reducing agent, wherein the mass ratio of the water-reducing agent to the hemihydrate gypsum is 0.1 to 1%, the content of particles having a particle diameter of 10 μm or less is 15 to 35 volume %, the content of particles having a particle diameter of 20 μm or less is 40 to 55 volume %, and the content of particles having a particle diameter of 30 μm or less is 55 to 75 volume %.

Aspects of the invention include a method of producing a cement material comprising step of: first reacting a calcium-bearing starting material with a first acid to produce an aqueous first calcium salt; second reacting the aqueous first calcium salt with a second acid to produce a solid second calcium salt; wherein the second acid is different from the first acid and the second calcium salt is different from the first calcium salt; and thermally treating the second calcium salt to produce a first cement material. Preferably, but not necessarily, during the second reacting step, reaction between the first calcium salt and the second acid regenerates the first acid.