Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
1999-12-06
2001-11-13
Green, Anthony (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S002000, C106S660000, C106S823000
Reexamination Certificate
active
06315825
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to cementitious products such as concrete, mortar, grout, and the like, and concrete products such as paving, paving blocks, concrete pipe, concrete blocks, cellular concrete, extruded concrete and roofing material, shot crete and concrete statuary; and more particularly to an improved cementitious composition and process for producing cemetitious products having improved resistance to water penetration and other deleterious elements and agents.
2. Description of Related Art
Concrete is a widely used engineering construction material, generally comprising a cementing or bonding substance, usually cement, and most commonly portland cement; aggregate, such as gravel, stone and/or sand; and water. Other cementitious products, such as mortar or grout are made by varying the type of aggregate employed. The cementing substance, particularly hydraulic cement, usually reacts chemically with water to form a hard, stonelike mass, which during concurrent mixing with aggregate, forms concrete, mortar and other cementitious products.
While cementitious products, such as concrete, particularly as used for pavement, bridges, walls, dams and the like, are relatively durable, they deteriorate over time, often due to the penetration of water into the product, particularly due to the porous nature of the product. Excess water is always used in a concrete mix in order to facilitate pouring and placement of the concrete. If the exact amount of water needed to hydrate the cement is used, the concrete would not be pourable or placeable. The excess water found in the mix is non-compressible and substantially evaporates from the concrete as it cures, and the resultant mass becomes porous as evaporation progresses. The porosity further diminishes the durability of the concrete, providing locations for water to penetrate the concrete. In climates where freezing temperatures periodically occur, the water in the product tends to freeze during such periods, and when frozen expands, often causing cracks, spalling and accellerated disintegration of the product. The deterioration is particularly noticeable where metal is used for reinforcement of the concrete products, for example, in the form of reinforcing mesh or rods, for example “rebars” in concrete pavement and the like. Over time, water penetrates through the concrete which corrodes metal reinforcement, often causing visible stains on the surface of the product, as well as weakening of the structure of the product.
In prior attempts to reduce water penetration, detergents have been mixed into the mixture of water, cementing substance and aggregate, but the result has been only marginally decreasing the porosity of the resulting product. Other known additives such as pozzolanic materials and metal salts of fatty acids provide only marginal improvement in water resistance, and also decrease the strength of the product during curing.
Quality concrete has surfactants added to the mix. Surfactants decrease the need for excess water, while making the concrete mix pourable as if the added amount of excess water was present. The pourability of the concrete mix is referred to as “slump”. These surfactants are known as water-reducers, plasticizers and in some cases “super-plasticizers”. When surfactants are introduced into the concrete, the result is a less porous and somewhat stronger product. The strength increase is attributed to lower water/cement ratio and decrease in porosity. While surfactants improve the resistance to water penetration, surfactants alone provide too little improvement to be considered a solution to the problem.
Another proposal to reduce water penetration has been the introduction into the composition of a glycol ester of a C
8
-C
22
fatty acid, such as the polyethyleneglycol ester of stearic acid, as in U.S. Pat. No. 4,878,948. The resulting product provides only incremental improvement in water penetration. Other attempts at reducing water penetration of cementitious products have utilized surface treatments, using such treatments as aqueous dispersions of film forming synthetic polymers and coagulants, film forming water-based, wax-free emulsions of a C
4
linear polymer composition used for both wood and concrete surfaces, and paraffin wax in solvent coatings. These surface treatments are impractical with large surfaces, such as pavements, and are ineffective over a period of time due to wear and erosion of the coating due to climatic elements and ultraviolet deterioration.
Therefore, there is a need for compositions and a process for substantially improving the water resistance of cementitious products, which compositions and process do not decrease the strength and other properties of the products.
SUMMARY OF THE INVENTION
Therefore, it is one object of the present invention to provide a composition which substantially improves the resistance of cementitious products to the penetration of water.
It is another object of the present invention to provide a process for the production of cementitious products which have improved resistance to the penetration of water.
It is still another object of the present invention to provide compositions and a process to reduce the amount of water required in the production of cementitious products which have improved resistance to the penetration of water.
Still another object of the present invention is to provide compositions and a process for improving the resistance against mildew on the surface of cementitious products.
Another object of this invention is to provide compositions and a process for improving the flowability of cementitious compositions.
Still another object of the invention is to provide compositions and a process for improving the resistance of cementitious products to the growth of algae on their surface.
Another object of the invention is to provide compositions and a process for improving the resistance of cementitious products containing certain additives to deterioration from ultraviolet radiation of those additives within the products.
Still another object of the invention is to provide compositions and a process for improving the durability of cementitious products against deterioration as a result of cyclical freezing and thawing.
Another object of the present invention is to provide compositions and a process for providing cementitious products having lower weight per volume than cementitious products of the prior art.
It is still another object of this invention to provide compositions and a process which efficiently provide a vehicle for instituting property enhancing agents into cementitious products while improving the resistance of the cementitious products to the penetration and/or absorption of water into the products.
These and other objects and advantages of the present invention will be apparent from the following description.
In accordance with the present invention a process is provided for improving the resistance of a cementitious product to the penetration of water into the product in which a minor amount of an aqueous emulsion of a waxy substance or of rosin is combined with a major amount of water to form a substantially aqueous mixture which is utilized as the aqueous ingredient in the preparation of the cementitious product. For convenience, both rosin and waxy substances useful in the present invention are referred to as “waxy substance”, and emulsions of both a waxy substance or of rosin are referred to herein as “emulsion of a waxy substance”, unless otherwise described. The composition of the present invention comprises an aqueous mixture including an aqueous emulsion of a waxy substance in an amount sufficient to improve the resistance to the penetration of water in a cementitious product admixed with cement and aggregate.
It is surprising and unexpected that the use of an aqueous emulsion of a waxy substance in the composition of water, cement and aggregate to form the cementitious product provides improved resistance to the penetration of water while substan
Great Barrier Technologies, Inc.
Green Anthony
Welsh & Katz Ltd.
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