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US 5,690,729 AGranted
Cement mixtures with alkali-intolerant matter and method
AssigneeMaterials Technology Corporation
InventorRoger H. Jones, Jr.
Life of this patent
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AssigneeMaterials Technology Corporation
InventorRoger H. Jones, Jr.
Estimating the term…
A method of reinforcing cement/concrete mixtures with alkali-intolerant reinforcements and/or aggregate, such as uncoated, common glass filament, plastic filament, fabric and roving made therefrom by reducing the pH of the mixture while in its plastic state, and/or after it has set and cured, to about 7. With a neutral pH, the alkali-intolerant reinforcements need not be coated to protect them from degradation. In the absence of alkalinity, the reinforcement and/or aggregate material bonds with the cement mixture to form a relatively stronger mixture, which can be shaped as desired, made part of permanently poured structures, cement boards and many other small and large products. By selecting appropriate and, if desired, different materials for the reinforcements and/or aggregate, the strength, flexibility, etc. characteristics of the product can be readily changed to adapt the product to the intended use. The pH is reduced by migrating such materials as CO.sub.2 and/or CO and O.sub.3 into the cement after it has cured and, if desirable, also during curing. The CO.sub.2 and/or CO and O.sub.3 for the chemical reactions to reduce the pH are most suitably obtained from flue gases of independent combustion processes which would otherwise be discharged as atmospheric pollutants.
A method of protecting alkali-intolerant material in a cured cement product comprising the steps of mixing dry cement, ground calcite, and an alkali-sensitive material, adding water to form a paste, molding the paste into a product, curing the product, exposing the cured product to carbon dioxide, and reducing the pH of the mixture to about 7 by generating calcium carbonate in calcite form.
A method of reinforcing cured cement mixtures with a material having alkali-intolerant or alkali-sensitive exterior surfaces comprising the steps of mixing at least cement, water, calcite and the material to form a paste, shaping the paste into a product, curing the product, exposing the cured product to carbon dioxide or carbon monoxide drying the product, and continuing the carbon dioxide exposing step until substantially all calcium hydroxide has reacted into calcite and the pH of the product is about 7.
A method of providing cured cement mixtures with material having alkali-intolerant exterior surfaces comprising the steps of mixing dry cement powder, ground calcite, and an alkali-sensitive material, adding water to form a paste, shaping the paste into a product, curing the product, exposing the product to a carbon dioxide atmosphere, and drying and repeating the carbon dioxide exposing step until substantially all calcium hydroxide has reacted into calcite and the pH of the product is reduced to about 7 as a result of converting calcium hydroxide which is present in the product into calcite.
A method of reinforcing cured cement mixtures with fibers having alkali-intolerant exterior fiber surfaces comprising the steps of mixing dry cement powder, ground calcite, and alkali-sensitive fibers and adding water to form a paste therewith, shaping the paste into a product, curing the product, exposing the cured product to carbon dioxide, drying and repeating the carbon dioxide exposing step until substantially all calcium hydroxide has reacted into calcite, the stable form of calcium carbonate, and reducing the pH of the product to about 7.
A method of protecting alkali-intolerant material in a cured cement product against degradation of the material by calcium hydroxide comprising the steps of mixing dry cement powder, ground calcite, and alkali-sensitive materials and adding water to form a paste therewith, shaping the paste into a product, curing the product, exposing the cured product to a carbon dioxide atmosphere by using flue gases from a combustion process of at least one of CO and CO.sub.2 and mixtures thereof, reacting at least one of CO and CO.sub.2 with calcium hydroxide in the product to form calcium carbonate as substantially calcite in an amount sufficient to reduce the pH of the mixture to about 7, and continuing the exposing step until substantially all calcium hydroxide has reacted into calcite.
A cured cement product comprising at least cement, a filler, and material distributed throughout the product which has alkali-intolerant exterior surfaces in contact with a remainder of the product, the product including calcium carbonate in the form of substantially calcite, having a pH of about 7 and made by mixing dry cement powder, ground calcite, and an alkali-sensitive material and adding water to form a paste therewith, shaping the paste into the product, curing the product, and exposing the cured product to carbon dioxide until substantially all calcium hydroxide has reacted into calcite.
A cured cement product comprising at least cement including calcium carbonate in the form of calcite and at least one of fibers and aggregate distributed throughout the product and having alkali-intolerant exterior surfaces in contact with a remainder of the product, some of the at least one of the fibers and the aggregate being made from a different material than others of the at least one of the fibers and the aggregate, the product being made by mixing dry cement powder, ground calcite, and an alkali-sensitive material and adding water to form a paste therewith, shaping the paste into the product, curing the product, and exposing the cured product to carbon dioxide until substantially all calcium hydroxide has reacted into calcite and having a pH about 7.
Dependencies are inferred from the claim text.