The present invention provides a method of preparing a recycled cementitious material by a phosphogypsum-assisted carbon sequestration pretreatment process. The method includes: (1) placing 100 mass parts of phosphogypsum, 1 to 2 mass parts of grinding aid, 10 to 20 mass parts of sodium-containing alkali component, 150 to 300 mass parts of zirconia balls, and 150 to 300 mass parts of water into a wet grinding tank for wet grinding. After 10 min to 30 min of wet grinding, introducing CO.sub.2 at a flow rate of 1.5 to 2.2 mass parts/min to keep a temperature of a wet grinding slurry below 40 C. When the wet grinding slurry reaches pH=10, ending the wet grinding and sieving out a wet grinding slurry; (2) mixing the wet grinding slurry with 700 to 1000 mass parts of slag and 100 to 350 mass parts of water to obtain a recycled cementitious material.

The present invention provides a method of preparing a recycled cementitious material by a phosphogypsum-assisted carbon sequestration pretreatment process. The method includes: (1) placing 100 mass parts of phosphogypsum, 1 to 2 mass parts of grinding aid, 10 to 20 mass parts of sodium-containing alkali component, 150 to 300 mass parts of zirconia balls, and 150 to 300 mass parts of water into a wet grinding tank for wet grinding. After 10 min to 30 min of wet grinding, introducing CO.sub.2 at a flow rate of 1.5 to 2.2 mass parts/min to keep a temperature of a wet grinding slurry below 40 C. When the wet grinding slurry reaches pH=10, ending the wet grinding and sieving out a wet grinding slurry; (2) mixing the wet grinding slurry with 700 to 1000 mass parts of slag and 100 to 350 mass parts of water to obtain a recycled cementitious material.

A gypsum wallboard having a core with a central core layer and one or more densified layers is disclosed. At least one densified layer contains salt absorbent particles of zeolite and/or hydrotalcite to improve adhesion of the gypsum core to a cover sheet. Also, methods of making the gypsum wallboard and a wall system for employing the gypsum wallboard are disclosed.

Provided is a composite material including a blend of components. The blend includes phosphogypsum, bitumen and particulate matter. The phosphogypsum may be present in an amount of at least 10% w/w out of the total weight of said composite material. Also provided herein is a method of producing the composite material, by, at least, mixing phosphogypsum and particulate matter at a temperature above 150 C. for a time sufficient to receive an essentially dry particulate mixture in which the amount of the phosphogypsum is such to obtain a composite material having at least 10% w/w out of the total dry weight of said composite material. While mixing molten bitumen may be introduced into the essentially dry particulate mixture to obtain the composite material. Articles of manufacture including the composite material are also disclosed.

Provided is a practically valuable and economically excellent insolubilizing material for a specific toxic substance: that is useful for insolubilizing treatment for a heavy metal or the like conducted by applying the insolubilizing material for a specific toxic substance to soil or on the surface of the soil; that is capable of effectively insolubilizing and immobilizing the heavy metal or the like; that is capable of making treated matter neutral so as to be reusable and environment-friendly; and moreover that is capable of imparting strength to the treated matter as necessary; and with which the heavy metal or the like is not re-eluted even when the treated matter is exposed to an environment under a neutral condition or an acidic condition. An insolubilizing material for a specific toxic substance to be used so that soil does not reach a strongly alkaline region of a pH of 11 or more, wherein the insolubilizing material for a specific toxic substance comprises an amorphous aluminum compound or a derivative thereof as a main component, or an insolubilizing material for a specific toxic substance to be used so that soil containing a heavy metal or the like does not reach a strongly alkaline region of a pH of 11 or more, the insolubilizing material for a specific toxic substance functioning also as a solidifying material, wherein the insolubilizing material for a specific toxic substance comprises gypsum obtained by adding and mixing, to the gypsum, the amorphous aluminum compound and the derivative thereof in a range of 0.5 to 60 mass parts relative to 100 mass parts of the gypsum, and a method for improving soil using the insolubilizing material for a specific toxic substance.

Provided is a practically valuable and economically excellent insolubilizing material for a specific toxic substance: that is useful for insolubilizing treatment for a heavy metal or the like conducted by applying the insolubilizing material for a specific toxic substance to soil or on the surface of the soil; that is capable of effectively insolubilizing and immobilizing the heavy metal or the like; that is capable of making treated matter neutral so as to be reusable and environment-friendly; and moreover that is capable of imparting strength to the treated matter as necessary; and with which the heavy metal or the like is not re-eluted even when the treated matter is exposed to an environment under a neutral condition or an acidic condition. An insolubilizing material for a specific toxic substance to be used so that soil does not reach a strongly alkaline region of a pH of 11 or more, wherein the insolubilizing material for a specific toxic substance comprises an amorphous aluminum compound or a derivative thereof as a main component, or an insolubilizing material for a specific toxic substance to be used so that soil containing a heavy metal or the like does not reach a strongly alkaline region of a pH of 11 or more, the insolubilizing material for a specific toxic substance functioning also as a solidifying material, wherein the insolubilizing material for a specific toxic substance comprises gypsum obtained by adding and mixing, to the gypsum, the amorphous aluminum compound and the derivative thereof in a range of 0.5 to 60 mass parts relative to 100 mass parts of the gypsum, and a method for improving soil using the insolubilizing material for a specific toxic substance.

The invention relates to a method for binding of carbon dioxide, comprising: providing a starting material which comprises sources for CaO and SiO.sub.2 and optionally also Al, Fe and/or Mg, hydrothermally treating the starting material in an autoclave at 50 to 300 C., tempering at 350 to 600 C., and hardening the resulting material with carbon dioxide. The invention further relates to building elements which are obtained by hardening a material according to the method.

The invention relates to a method for binding of carbon dioxide, comprising: providing a starting material which comprises sources for CaO and SiO.sub.2 and optionally also Al, Fe and/or Mg, hydrothermally treating the starting material in an autoclave at 50 to 300 C., tempering at 350 to 600 C., and hardening the resulting material with carbon dioxide. The invention further relates to building elements which are obtained by hardening a material according to the method.

A method of producing composites from inorganic materials by processing with thermoplastic forming techniques mixtures containing one or more inorganic, fine residual materials and one or more polymers based on ethylenically unsaturated monomers in the form of protective colloid-stabilized, water-redispersible polymer powders, wherein the inorganic, fine residual materials are based on inorganic materials selected from the group consisting of gypsum, lime, talc, silicas, kaolins, silicates and titanium dioxide, and wherein the composites are based on from 5 to 80% by weight of polymers based on ethylenically unsaturated monomers and from 20 to 95% by weight of inorganic, fine residual materials, based on the total weight of polymer based on ethylenically unsaturated monomers and inorganic, fine residual materials.

A method of producing composites from inorganic materials by processing with thermoplastic forming techniques mixtures containing one or more inorganic, fine residual materials and one or more polymers based on ethylenically unsaturated monomers in the form of protective colloid-stabilized, water-redispersible polymer powders, wherein the inorganic, fine residual materials are based on inorganic materials selected from the group consisting of gypsum, lime, talc, silicas, kaolins, silicates and titanium dioxide, and wherein the composites are based on from 5 to 80% by weight of polymers based on ethylenically unsaturated monomers and from 20 to 95% by weight of inorganic, fine residual materials, based on the total weight of polymer based on ethylenically unsaturated monomers and inorganic, fine residual materials.