Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
2001-10-19
2003-11-25
Green, Anthony J. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S002000, C106S015050, C106S016000, C106S018290, C106S660000, C106S823000
Reexamination Certificate
active
06652643
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 We concrete, extruded concrete 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 accelerated 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 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.
There is a further need for improving the early strength of cementitious products, i.e., cement aggregate products. It is known that cement aggregate products, particularly such cement aggregate products as blocks, concrete masonry units and concrete pavers, achieve acceptable strength to permit their being shipped and used only after a relatively long period, usually a number of days. Such cement aggregate products, as blocks concrete masonry units and concrete pavers, are produced by pouring a mix of cement, aggregate and water into a mold. The least amount of water is utilized to permit the mix to be placed in the mold, so that the product will retain its shape upon removal after few seconds in the mold. The molded product is then placed on curing racks and allowed to remain on the racks, often while being heated, for a relatively lengthy period, until sufficient strength, usually approximately 1000 psi for concrete masonry units is attained so the products can be shipped and used.
Attempts have been made to increase the early strength of cement aggregate products, particularly concrete blocks, concrete masonry units, and the like, by adding an accelerator, such as calcium chloride triethanolamine or sodium silicate, to the mix or subjecting the product to steam or using type III cement. However, the addition of these accelerators, or the use of steam, increases the cost of producing the product and often its production time.
Thus, increasing the early strength of the product is advantageous in reducing the time and cost required for producing a shippable and usable product.
It is also known that cementitious products exposed to the elements and/or in moist conditions are subject to the growth of mildew and mold on their surfaces, detracting from their appearance and eventually to their discoloration and deterioration. Therefore, there is a need for cement aggregate products having improved resistance to the growth of mildew and mold in addition to improving the resistance of the products to the penetration and absorption of water.
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 and mold on the surface of cementitious products.
An object of this invention is to provide compositions and a process for improving the early strength of cement aggregate 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
Great Barrier Technologies, Inc.
Green Anthony J.
Welsh & Katz Ltd.
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