Water-based paint is used as a sacrificial agent to reduce the detrimental effect of carbon-containing fly ash on the entrainment of air in concrete. The invention provides a composition for reducing the effect of carbon contained in fly ash on air entrainment in cementitious mixtures comprising water, cement, fly ash and entrained air. The composition comprises water-based paint and one or more of pulverized or un-pulverized pozzolan, pulverized or un-pulverized cementitious solids, a superplasticizer, a defoamer, an air-entraining admixture, a water-reducing admixture, a retarding admixture, an accelerating admixture, a hydration control admixture and a rheology modifying admixture. The invention also provides a method of reducing the effect of carbon on air entrainment in carbon-containing fly ash, comprising mixing the fly ash with water-based paint.

A method for preparing concrete based on GGBS, silicon-aluminum compounds and CO.sub.2 waste gas includes: putting a certain quantity of GGBS, silicon-aluminum compounds and water into a ball milling tank; introducing CO.sub.2 waste gas into the tank, and stopping the introduction when gas pressure in the tank reaches a standard; and starting the ball milling tank, and repeating the gas charging and ball milling for multiple times until a median size reaches the standard and CO.sub.2 is completely reacted and adsorbed by the GGBS, and finally preparing concrete from a GGBS mixture meeting requirements. According to the method, by adding the silicon-aluminum compounds into the GGBS, and under a mechanical action of the ball milling machine, the GGBS is promoted to react with and adsorb CO.sub.2.

Herein discloses a method of carbonating reactive magnesia cement, which includes: (i) providing an aqueous suspension including a carbon dioxide-producing bacteria; (ii) mixing the aqueous suspension with a precursor which the carbon dioxide-producing bacteria generates carbon dioxide from for a duration to form an aqueous mixture sufficient for substantially carbonating the reactive magnesia cement; (iii) mixing the aqueous mixture with the reactive magnesia cement to form a blend; wherein a nutrient is provided in the aqueous suspension of step (i) or in the reactive magnesia cement of step (iii) to sustain the carbon dioxide-producing bacteria in the reactive magnesia cement; and (iv) curing the blend to carbonate the reactive magnesia cement. A reactive magnesia cement composite formed by the method is also disclosed.

Herein discloses a method of carbonating reactive magnesia cement, which includes: (i) providing an aqueous suspension including a carbon dioxide-producing bacteria; (ii) mixing the aqueous suspension with a precursor which the carbon dioxide-producing bacteria generates carbon dioxide from for a duration to form an aqueous mixture sufficient for substantially carbonating the reactive magnesia cement; (iii) mixing the aqueous mixture with the reactive magnesia cement to form a blend; wherein a nutrient is provided in the aqueous suspension of step (i) or in the reactive magnesia cement of step (iii) to sustain the carbon dioxide-producing bacteria in the reactive magnesia cement; and (iv) curing the blend to carbonate the reactive magnesia cement. A reactive magnesia cement composite formed by the method is also disclosed.

The present invention relates to a process for providing a fiber cement product, the process comprising the steps of (a) providing an uncured fiber cement product, (b) curing the uncured fiber cement product, (c) optionally abrasive blasting of at least part of the surface of the cured fiber cement product, (d) treating the cured fiber cement product with CO2 (so-called carbonation) at a concentration of 0.01 to 100%, at a temperature of 5 to 90° C., relative humidity of to 99% for a period of 1 minute to 48 hours. The obtained fiber cement products show less efflorescence.

A method of carbonating cement powder and use thereof. An amount of water is supplied to an initial cementitious powder to create a moistened cementitious powder. Carbon dioxide is supplied to the moistened cementitious powder, while mechanically stirring the moistened cementitious powder, to cause a reaction of the carbon dioxide with the moistened cementitious powder to produce a carbonated cementitious material. The carbonated cementitious material is dried and ground to produce a carbonated cementitious powder. The carbonated cementitious powder may be combined with ordinary cement and various ingredients or additives, such as retarders, accelerators and extenders for use in well cementing applications. Methods for cementing casing, liners and remedial operations such as plugging back, and squeeze cementing are also provided. Methods for producing a low alkaline cement suitable for high CO.sub.2 gas wells are also provided. Methods to achieve a stable retarded cement used in higher temperatures are provided.

Methods of preparing a cementitious structure for carbon dioxide (CO.sub.2) sequestration are provided. The cementitious structure may be a cast in a mold. First, a cementitious composite material comprising binder and water is conditioned, for example, in a mold by exposing the cementitious composite material to ≥about 50% to ≤about 80% relative humidity for ≥about 3 hours to ≤about 24 hours. The cementitious composite material is then dried to remove ≥about 10% by weight of initial water in the cementitious composite material. The cementitious structure formed is capable of a carbon dioxide uptake level of greater than or equal to about 6% by weight binder. The cementitious structure has a tensile strain capacity of ≥about 1% and a uniaxial tensile strength of ≥about 1 MPa. The method may also include carbonating the cementitious structure, following by an optional further hydration process.

Methods of preparing a cementitious structure for carbon dioxide (CO.sub.2) sequestration are provided. The cementitious structure may be a cast in a mold. First, a cementitious composite material comprising binder and water is conditioned, for example, in a mold by exposing the cementitious composite material to ≥about 50% to ≤about 80% relative humidity for ≥about 3 hours to ≤about 24 hours. The cementitious composite material is then dried to remove ≥about 10% by weight of initial water in the cementitious composite material. The cementitious structure formed is capable of a carbon dioxide uptake level of greater than or equal to about 6% by weight binder. The cementitious structure has a tensile strain capacity of ≥about 1% and a uniaxial tensile strength of ≥about 1 MPa. The method may also include carbonating the cementitious structure, following by an optional further hydration process.

Provided herein are compositions and methods of carbonation processing for the fabrication of cementitious materials and concrete products. Embodiments include manufacturing processes of a low-carbon concrete product comprising: forming a cementitious slurry including portlandite; shaping the cementitious slurry into a structural component; and exposing the structural component to a CO.sub.2 waste stream, thereby enabling manufacture of the low-carbon concrete product.

Provided herein are compositions and methods of carbonation processing for the fabrication of cementitious materials and concrete products. Embodiments include manufacturing processes of a low-carbon concrete product comprising: forming a cementitious slurry including portlandite; shaping the cementitious slurry into a structural component; and exposing the structural component to a CO.sub.2 waste stream, thereby enabling manufacture of the low-carbon concrete product.