The invention provides novel apparatus and processes for gas flow and conditioning to achieve optimal CO.sub.2 curing of articles of composite materials (e.g., precast objects made of carbonatable calcium silicate-based cements), with solid interior or having hollow interior ducts, channels and chambers or otherwise being hollowed out, as well as the precast objects so made, which are suitable for a variety of applications in construction, pavements and landscaping, and infrastructure.

The present invention provides a wet press process and admixture components for making concrete slabs (flags) (16), curb (kerb) units, panels, boards, and other flat shapes, whereby colloidal silica and at least one alkanolamine and optional rheology control components are employed to provide an ideal combination of pressing time, green strength, surface definition, stack-ability, final concrete strength, and permeability. Stack-ability can be expressed in terms of minimum deflection or non-eccentricity of the units while standing on thickness edges at distances apart less than width or standing height. A wet press process typically involves introducing a highly fluid concrete mix into a mold (10,12), applying hydraulic pressure to consolidate the concrete (e.g., 1000-3000 PSI) and to extract excess water, removing the pressed concrete (16) while in a green state from the mold (10,12), and then standing the slab (16) units immediately upon removal from the mold (10,12) while in a green state, on an edge adjacent to but spaced apart from other edge-standing units. In further embodiments, rounded aggregates such as naturally occurring sand and/or gravel obtained from local sources can be incorporated into the concrete slabs without defeating (vertical) stack-ability in the green state.

The present invention provides a wet press process and admixture components for making concrete slabs (flags) (16), curb (kerb) units, panels, boards, and other flat shapes, whereby colloidal silica and at least one alkanolamine and optional rheology control components are employed to provide an ideal combination of pressing time, green strength, surface definition, stack-ability, final concrete strength, and permeability. Stack-ability can be expressed in terms of minimum deflection or non-eccentricity of the units while standing on thickness edges at distances apart less than width or standing height. A wet press process typically involves introducing a highly fluid concrete mix into a mold (10,12), applying hydraulic pressure to consolidate the concrete (e.g., 1000-3000 PSI) and to extract excess water, removing the pressed concrete (16) while in a green state from the mold (10,12), and then standing the slab (16) units immediately upon removal from the mold (10,12) while in a green state, on an edge adjacent to but spaced apart from other edge-standing units. In further embodiments, rounded aggregates such as naturally occurring sand and/or gravel obtained from local sources can be incorporated into the concrete slabs without defeating (vertical) stack-ability in the green state.

Compositions and methods for carbonation curing of cement and/or concrete are provided, where a lixiviant species that solubilizes calcium from oxides and silicates provided with the cement or concrete is included in the curing cement or concrete mixture. Reaction of solubilized calcium with carbon dioxide results in the formation of insoluble calcium carbonate that is incorporated into the structure of the cured cement or concrete, and simultaneously regenerates the lixiviant species. Rapid reaction of carbon dioxide within the curing cement or concrete further generates a concentration gradient that accelerates uptake of additional carbon dioxide, for example from ambient air. This incorporation of environmental carbon also causes the cured cement or concrete to be used for long term carbon sequestration.

Calcium silicate-based cements and concretes are disclosed, which result in concrete compositions that have an improved strength development. A cement product includes a plurality of particles of a carbonatable calcium silicate cement and a first additive; wherein, the first additive is an organic molecule with at least one primary, secondary or tertiary amine group.

Systems for accelerated carbonation curing of a pre-cast cementitious structure may include an ejector and a curing chamber downstream of the ejector. The ejector may be operable to combine a lesser-pressure carbon dioxide containing stream from a carbon dioxide source with a greater-pressure steam to produce a mixed stream including at least steam and carbon dioxide. The mixed stream may have a pressure greater than the pressure of the lesser-pressure carbon dioxide containing stream. The curing chamber may be operable to receive the mixed stream from the ejector and contact the mixed stream with the pre-cast cementitious structure to cure the pre-cast cementitious structure. Processes for accelerated carbonation curing of pre-cast cementitious structures using the systems are also disclosed.

The invention comprises a concrete form. The form comprises a first concrete forming panel having a first primary surface adapted for forming and contacting plastic concrete and a second primary surface opposite the first primary surface; a layer of insulating material contacting and substantially covering the second primary surface of the first concrete forming panel; and an insulating blanket adjacent the first concrete forming panel. A method of using the concrete form is also disclosed.

The invention comprises a concrete form. The form comprises a first concrete forming panel having a first primary surface adapted for forming and contacting plastic concrete and a second primary surface opposite the first primary surface; a layer of insulating material contacting and substantially covering the second primary surface of the first concrete forming panel; and an insulating blanket adjacent the first concrete forming panel. A method of using the concrete form is also disclosed.

Provided is a cement composition that has high fluidity (for example, a 0-drop flow value of 200 mm or more) before curing and exhibits high compressive strength (for example, 320 N/mm.sup.2 or more) after curing. The cement composition includes a cement, a silica fume having a BET specific surface area of from 10 m.sup.2/g to 25 m.sup.2/g, an inorganic powder having a 50% cumulative particle size of from 0.8 μm to 5 μm, a fine aggregate having a maximum particle size of 1.2 mm or less, a water reducing agent, an antifoaming agent, and water. The ratio of the cement is from 55 vol % to 65 vol %, the ratio of the silica fume is from 5 vol % to 25 vol %, and the ratio of the inorganic powder is from 15 vol % to 35 vol % in the total amount of 100 vol % of the cement, the silica fume, and the inorganic powder.

In some embodiments, a method may include preparing building forms including at least some cementitious materials. The method for preparing forms may include mixing substantially dry cementitious material particles with closed cell foam particles to form a substantially dry composition. In some embodiment, at least some of the cementitious material particles may adhere to at least some surface deformations on the surface of the closed cell foam particles. In some embodiments, the method may include mixing a second portion of water with the substantially dry composition for a second period of time to form a partially wet composition. In some embodiments, a method may include forming a building form including at least some cementitious materials from the partially wet composition. In some embodiments, the closed cell foam particles may include expanded polystyrene. In some embodiments, a ratio of the water to cementitious material particles may range from 0.20 to 0.40.