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 describes a hydraulic cement composition, process and use thereof, wherein the composition comprises a hydraulic cement composition with increased resistance against carbon dioxide (CO.sub.2) for application in reservoirs such as oil and gas and carbon capture and storage (CCS) wells; with improved performance of cement paste formulations as a material for application in primary, secondary cementing, recovery and/or plugging operations, of reservoirs/wells that operate with high CO.sub.2 content; as a technological alternative to guarantee the integrity of wells in CO.sub.2-rich environments for long periods of time, without any additional intervention to the already current operational procedures for cementing wells, and with cost reduction in relation to class G cement (currently, the main raw material); and sufficient chemical resistance to carry out enhanced oil (EOR) and gas (EGR) recovery by injecting high levels of CO.sub.2, increasing reservoir pressure throughout the extraction period of hydrocarbon reservoirs.

Method for grinding a solid in a vertical roller mill (VRM) and a cement composition prepared by the disclosed methods. A method comprises grinding a solid comprising a cement clinker under a water spray in the presence of a grinding stabilizing additive, wherein the grinding stabilizing additive comprises: (i) an alkanol amino acid compound or a disodium or dipotassium salt thereof having the structural formula:

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(ii) a glycol; or a mixture of (i) and (ii), wherein the water spray level is reduced by at least 5% compared to a control. Cement compositions prepared by the disclosed methods have the pre-hydration level (W.sub.k) equal to or less than 1.5%. The values and preferred values of R.sup.1-3 are disclosed herein.

The invention comprises a method of sequestering carbon dioxide. The method comprises delivering hyaloclastite, a volcanic glass or pumice to a mill capable of reducing the particle size of the hyaloclastite, a volcanic glass or pumice; processing the hyaloclastite, a volcanic glass or pumice in the mill so that the processed hyaloclastite, a volcanic glass or pumice has a volume-based mean particle size of less than or equal to 40 ?m; and exposing the hyaloclastite, a volcanic glass or pumice to carbon dioxide in gaseous, liquid or solid form during or after the particle reduction process.

The present invention describes a hydraulic cement composition, process and use thereof, wherein the composition comprises a hydraulic cement composition with increased resistance against carbon dioxide (CO.sub.2) for application in reservoirs such as oil and gas and carbon capture and storage (CCS) wells; with improved performance of cement paste formulations as a material for application in primary, secondary cementing, recovery and/or plugging operations, of reservoirs/wells that operate with high CO.sub.2 content; as a technological alternative to guarantee the integrity of wells in CO.sub.2-rich environments for long periods of time, without any additional intervention to the already current operational procedures for cementing wells, and with cost reduction in relation to class G cement (currently, the main raw material); and sufficient chemical resistance to carry out enhanced oil (EOR) and gas (EGR) recovery by injecting high levels of CO.sub.2, increasing reservoir pressure throughout the extraction period of hydrocarbon reservoirs.

A method for obtaining microcement and the microcement obtained thereof, by means of using a closed-circuit mill with high-efficiency separators (second generation with cyclones for dust collection), thus allowing to produce at a very low cost, showing excellent properties and quality of the microcement obtained thereof.

The present invention describes a hydraulic cement composition, process and use thereof, wherein the composition comprises a hydraulic cement composition with increased resistance against carbon dioxide (CO.sub.2) for application in reservoirs such as oil and gas and carbon capture and storage (CCS) wells; with improved performance of cement paste formulations as a material for application in primary, secondary cementing, recovery and/or plugging operations, of reservoirs/wells that operate with high CO.sub.2 content; as a technological alternative to guarantee the integrity of wells in CO.sub.2-rich environments for long periods of time, without any additional intervention to the already current operational procedures for cementing wells, and with cost reduction in relation to class G cement (currently, the main raw material); and sufficient chemical resistance to carry out enhanced oil (EOR) and gas (EGR) recovery by injecting high levels of CO.sub.2, increasing reservoir pressure throughout the extraction period of hydrocarbon reservoirs.

The invention comprises a method of sequestering carbon dioxide. The method comprises delivering hyaloclastite, a volcanic glass or pumice to a mill capable of reducing the particle size of the hyaloclastite, a volcanic glass or pumice; processing the hyaloclastite, a volcanic glass or pumice in the mill so that the processed hyaloclastite, a volcanic glass or pumice has a volume-based mean particle size of less than or equal to 40 m; and exposing the hyaloclastite, a volcanic glass or pumice to carbon dioxide in gaseous, liquid or solid form during or after the particle reduction process.

A method of producing cement clinker and a second calcined material, wherein the cement clinker is produced in a first production line and the second calcined material is produced from a raw material in a second production line by carrying out the following procedures e) optionally drying the raw material in a dryer, g) calcining the optionally dried raw material in a rotary kiln to obtain the second calcined material, wherein the sensible heat of a hot gas in the first production line is used as a heat source in the calcining step g) for calcining the raw material, and wherein the rotary kiln exhaust gas coming from the calcining step g) is introduced into the first production line for the secondary combustion of the rotary kiln exhaust gas.