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 manufacturing process of a concrete product includes: (1) extracting calcium from solids as portlandite; (2) forming a cementitious slurry including the portlandite; (3) shaping the cementitious slurry into a structural component; and (4) exposing the structural component to carbon dioxide sourced from a flue gas stream, thereby forming the concrete product.

A manufacturing process of a concrete product includes: (1) extracting calcium from solids as portlandite; (2) forming a cementitious slurry including the portlandite; (3) shaping the cementitious slurry into a structural component; and (4) exposing the structural component to carbon dioxide sourced from a flue gas stream, thereby forming the concrete product.

A sieve with a mesh opening of 75 to 20 m is provided. A raw fly ash powder is separated into a component remaining on the sieve and a component passing through the sieve by classification using the sieve. A fine fly ash powder, which is the component passing through the sieve, is used as a cement admixture. A coarse fly ash powder, which is the component remaining on the sieve, is used for production of cement clinker.

A sieve with a mesh opening of 75 to 20 m is provided. A raw fly ash powder is separated into a component remaining on the sieve and a component passing through the sieve by classification using the sieve. A fine fly ash powder, which is the component passing through the sieve, is used as a cement admixture. A coarse fly ash powder, which is the component remaining on the sieve, is used for production of cement clinker.

A manufacturing process of a concrete product includes: (1) extracting calcium from solids as portlandite; (2) forming a cementitious slurry including the portlandite; (3) shaping the cementitious slurry into a structural component; and (4) exposing the structural component to carbon dioxide sourced from a flue gas stream, thereby forming the concrete product.

A manufacturing process of a concrete product includes: (1) extracting calcium from solids as portlandite; (2) forming a cementitious slurry including the portlandite; (3) shaping the cementitious slurry into a structural component; and (4) exposing the structural component to carbon dioxide sourced from a flue gas stream, thereby forming the concrete product.

A manufacturing process of a concrete product includes: (1) extracting calcium from solids as portlandite; (2) forming a cementitious slurry including the portlandite; (3) shaping the cementitious slurry into a structural component; and (4) exposing the structural component to carbon dioxide sourced from a flue gas stream, thereby forming the concrete product.

A manufacturing process of a concrete product includes: (1) extracting calcium from solids as portlandite; (2) forming a cementitious slurry including the portlandite; (3) shaping the cementitious slurry into a structural component; and (4) exposing the structural component to carbon dioxide sourced from a flue gas stream, thereby forming the concrete product.

A method of reducing the ammonia emission from an aluminium oxide comprises the step of contacting secondary aluminium oxide with a zeolite. Preferably the zeolite is a used or unused fluid catalytic cracking (FCC) catalyst such as zeolite Y. The invention also relates to a mixture comprising secondary aluminium oxide and a zeolite, wherein the zeolite is a used or unused fluid catalytic cracking (FCC) catalyst and that the composition has a gaseous ammonia emission of 1 mg NH.sub.3 per gram of composition and hour. Lastly, the invention is directed towards the use of a zeolite for reducing the ammonia emission from secondary aluminium oxide.