Concrete product with enhanced ornamental surface layer

TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION

0001This invention relates to the concrete product field and, more particularly, to a concrete product characterized by an ornamental surface layer with enhanced strength and appearance and a method for making such a concrete product.

BACKGROUND OF THE INVENTION

0002Concrete is currently utilized to make a number of building products including, but not limited to, manufactured stone veneer, cementitious siding and cementitious roofing tiles. <patcit id="pcit0001" dnum="US6790544B"><text>U.S. Patents 6,790,544 to Schmitz</text></patcit>, <patcit id="pcit0002" dnum="US5797238B"><text>5,797,238 to Berntsson et al</text></patcit>, <patcit id="pcit0003" dnum="US5435949B"><text>5,435,949 to Hwang</text></patcit>, <patcit id="pcit0004" dnum="US4877656B"><text>4,877,656 to Baskin </text></patcit>and <patcit id="pcit0005" dnum="US4235948B"><text>4,235,948 to Holmes </text></patcit>and published <patcit id="pcit0006" dnum="US20040175514A"><text>U.S. Patent application 2004/0175514 to Stiattesi </text></patcit>are all exemplary of state of the art concrete products and their methods of production.

0003In the past a manufactured stone veneer has been formed utilizing a mold having cavities with shapes simulating real stone. More specifically, the state of the art manufacturing process generally comprises painting the mold cavity with a pigmented slurry consisting of water, cement, certain iron oxides for color and a polymeric binder. Next, concrete is vibrated into the cavity over the pigmented slurry. The material is then allowed to cure and set before being removed from the mold. Upon removal, the product comprises a body consisting of an ornamental facing layer formed from the pigmented slurry and a concrete substrate layer formed from the concrete.

0004As the concrete is vibrated within the mold M, aggregate and cement paste migrate downward and air bubbles B are typically driven upward (see <figref idref="f0001">Figure 1</figref>). It should be appreciated, however, that the concrete layer C includes a high viscosity, compacted aggregate that resists the upward movement of the air bubbles B. As a result, at times one or more air bubbles become trapped at the interface I between the pigmented slurry S and the concrete C. This results in a number of detrimental effects.

0005More specifically, the pigmented slurry and resulting ornamental surface layer are typically thin. Air bubbles underneath the surface along the interface between the two layers significantly weaken the ornamental surface layer. As a consequence, the surface layer may become damaged during removal of the product from the mold, during packing of the product for shipping, during shipping, during installation or even during handling at any time. Where the damage is severe, the product must be scrapped. Further, while less severe damage may not require scrapping of the product, it can adversely effect the service life and customer satisfaction with the product. More specifically, small air bubbles can lead to the formation of small holes in the ornamental surface layer. Such holes deleteriously affect the natural ornamental appearance of the product.

0006The present invention relates to a concrete product and a method for its production that substantially reduces or eliminates problems produced by air bubbles becoming trapped along the interface between the pigmented slurry and the concrete during production of concrete products. As a result, the concrete products of the current invention are produced without surface holes and have a more natural appearance.

SUMMARY OF THE INVENTION

0007In accordance with the purposes of the present invention as described herein, an improved concrete product is provided. The concrete product comprises a body including (a) an ornamental surface layer, (b) an intermediate strengthening layer and (c) a concrete substrate layer. Generally the ornamental surface layer includes cement, a pigmenting agent, a polymeric binder and water. The intermediate strengthening layer includes a cementitious material, a pigmenting agent and a water reducer admixture comprising a hydroxylated carboxylic acid and a polycarboxylate plasticizer. The concrete substrate layer includes a material selected from a group consisting of white cement, gray cement and combinations thereof.

0008Both the ornamental surface layer and the intermediate strengthening layer include a pigmenting agent. The pigmenting agent may be selected from a number of known materials. Such pigmenting agents may be selected from a group of materials comprising manganese oxide, iron oxides, iron hydroxides, carbon, titanium dioxide, chromium oxide, zinc oxides, nickel or chromium rutiles, cobalt, copper, barium sulphate, barium manganate, or other known pigmenting agents as known to one skilled in the art, and combinations thereof. The polymeric binder of the ornamental surface layer may be selected from a group of materials comprising Alkyl benzene sulphonates, alkyl naphthalene sulphonates, lignin sulphonate, sulphated polyglycol ethers, melamine formaldehyde condensates, naphthalene formaldehyde condensates, gluconic acid, salts of low molecular weight, partially esterified styrene/maleic acid anhydride copolymers and copolymers of vinyl acetate, crotonic acid, or other binders known to one skilled in the art, and combinations thereof.

0009The cementitious material of the intermediate strengthening layer may be selected from a group of materials consisting of white cement, gray cement, fly ash and combinations thereof. The water reducer admixture typically includes hydroxylated carboxylic acid and polycarboxylate plasticizer. In addition, the intermediate strengthening layer typically includes silica sand and/or reinforcing fibers. The reinforcing fibers may be selected from a group of materials consisting of glass fibers (preferably alkali-resistant (AR) glass), metal fibers, carbon fibers, natural fibers, polymer fibers (such as polyester, polypropylene, nylon, PVA or other polymer fibers), and combinations thereof. Further, the intermediate strengthening layer may include a waterproofing agent, , which may be selected from a group of materials comprising calcium stearate, magnesium stearate, aluminum staearate, calcium myristate, calcium palmitate and calcium laurate or any other known waterproofing agent and combinations thereof. The intermediate strengthening layer typically has a viscosity of between about 2,300 to about 4,800 centipoise using a #4 Brookfield viscometer.

0010In accordance with still another aspect of the present invention, a method is provided for making a concrete product. The method comprises the steps of providing an ornamental surface layer in a product mold, adding a strengthening layer to the ornamental surface layer in the mold, adding a concrete substrate layer to the ornamental surface layer and the strengthening layer in the mold, allowing the ornamental surface layer, strengthening layer and concrete substrate layer to cure and removing the product from the mold.

0011In the following description there is shown and described a preferred embodiment of the invention, simply by way of illustration of one of the modes best suited to carry out the invention. As it will be realized, the invention is capable of other different embodiments and its several details are capable of modification in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

0012The accompanying drawing incorporated in and forming a part of the specification, illustrates several aspects of the present invention and together with the description serves to explain certain principles of the invention. In the drawing:

0013<figref idref="f0001">Figure 1</figref> is a schematical side elevational view illustrating how air bubbles may become trapped along the interface of the pigmented slurry layer and concrete layer in prior art methods of producing concrete products;

0014<figref idref="f0001">Figure 2</figref> illustrates the concrete product of the present invention wherein the intermediate strengthening layer acts as a buffer between the air bubbles trapped at the interface between the intermediate strengthening layer and the concrete substrate layer and the ornamental surface layer; and

0015<figref idref="f0001">Figure 3</figref> is a perspective view of the cured and finished concrete product.

0016Reference will now be made in detail to the present preferred embodiment of the invention, an example of which is illustrated in the accompanying drawing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

0017Reference is now made to <figref idref="f0001">Figure 3</figref> illustrating the concrete product 10 of the present invention. The illustrated concrete product is a manufactured cut stone. It should be appreciated, however, that the concrete product may assume substantially any other appropriate form including, but not limited to, a stone veneer plate, cementitious siding and cementitious roofing tiles.

0018In the illustrated embodiment the concrete product 10 includes a body 12. The body 12 includes three layers: an ornamental facing layer 14, an intermediate strengthening layer 16 and a concrete substrate layer 18.

0019The ornamental facing layer 14 is formed from a pigmented slurry comprising cement, a pigmenting agent, a polymeric binder and water. As described in USPs 5,199,986 and 5,853,476, which are incorporated herein by reference in their entirety, the pigmenting agent may be selected from a number of known materials. Such pigmenting agents may be selected from a group of materials comprising manganese oxide, iron oxides, iron hydroxides, carbon, titanium dioxide, chromium oxide, zinc oxides, nickel or chromium rutiles, cobalt, copper, barium sulphate, barium manganate, or other known pigmenting agents as known to one skilled in the art, and combinations thereof. The polymeric binder of the ornamental surface layer may be selected from a group of materials comprising Alkyl benzene sulphonates, alkyl naphthalene sulphonates, lignin sulphonate, sulphated polyglycol ethers, melamine formaldehyde condensates, naphthalene formaldehyde condensates, gluconic acid, salts of low molecular weight, partially esterified styrene/maleic acid anhydride copolymers and copolymers of vinyl acetate, crotonic acid, or other binders known to one skilled in the art, and combinations thereof. Typically, the slurry from which the ornamental surface layer 14 is made includes cement, pigmenting agent, polymeric binder and water prior to curing.

0020The intermediate strengthening layer 16 is also made from a slurry including a cementitious material, a pigmenting agent, a water reducer admixture and water. Typically the cementitious material is selected from a group of materials consisting of white cement, gray cement, fly ash and combinations thereof. The pigmenting agent is selected from a group of materials as described above. Typically the pigmenting agent used in the intermediate strengthening layer 16 matches the pigmenting agent used in the ornamental facing layer 14, It is possible, however, for certain applications, that different pigmenting agents may be used in order to achieve special coloring effects.

0021The water reducer admixture typically incorporates a hydroxylated carboxylic acid and a polycarboxylate plasticizer. Exemplary water reducer admixtures include but are not limited to Sika 2100 High Range Water Reducer and Sika Plastiment Water Reducer and Retarder.

0022The intermediate strengthening layer 16 may also incorporate optional additives. Such additives may include but are not limited to a water proofing agent, silica sand to enhance the ornamental appearance of the product and reinforcing fibers to increase the strength of the product. The reinforcing fibers may be selected from a group of materials consisting of glass fibers (preferably AR glass), metal fibers, carbon fibers, natural fibers, polymer fibers (such as polyester, polypropylene, nylon, PVA or other polymer fibers), and combinations thereof. Further, the intermediate strengthening layer may include a waterproofing agent, for example as disclosed in <patcit id="pcit0007" dnum="USP3563786A"><text>USP 3,563,786</text></patcit>, which is incorporated herein by reference in its entirety. Such a waterproofing agent may be selected from a group of materials comprising calcium stearate, magnesium stearate, aluminum staearate, calcium myristate, calcium palmitate and calcium laurate or any other known waterproofing agent and combinations thereof.

0023The intermediate strengthening layer 16 has a viscosity prior to cure of between about 2,300 and about 4,800 centipoise using a #4 Brookfield viscometer.

0024The concrete substrate layer 18 typically includes a material selected from a group consisting of white cement, gray cement and combinations thereof. The method of making the concrete product 10 will now be described in detail. The method includes providing an ornamental surface layer 14 by painting a pigmented slurry precursor on/in a product mold M. This may be done by spraying or brushing. Next is the adding of the strengthening layer 16 to the ornamental surface layer 14 in the mold M. Typically, this is done by spraying. This is followed by adding the concrete substrate layer 18 to the ornamental surface layer 14 and the strengthening layer 16 in the mold M. The next step involves allowing the three layers 14, 16 and 18 to cure and set. This is followed by removing the product 10 from the mold M.

0025As the concrete substrate layer 18 is added to the mold M, some air bubbles B are trapped under the added concrete (See <figref idref="f0001">Figure 2</figref>). Any large air bubbles B remaining in the product 10 after vibration are typically above the interface 20 between the intermediate strengthening layer 16 and the concrete substrate layer 18. Significantly, there are no air bubbles B adjacent the ornamental facing layer 14 or along the interface 22 between the ornamental facing layer 14 and the intermediate strengthening layer 16. In effect, the intermediate strengthening layer 16 acts as a buffer between the ornamental facing layer 14 and any air bubbles B that might possibly remain in the concrete product 10 following vibration of materials into the mold and the setting of a product. Together, the ornamental surface layer 14 and intermediate strengthening layer 16 provide a relatively thick, bubbleless cross section that is more robust and better resists stress on demolding.

0026Since, the resulting concrete product 10 does not include air bubble holes along the surface thereof, it has a more natural appearance. The absence of holes may also help inhibit the ability of water and ice to penetrate the product and induce spalling. The reduction or elimination of holes also tends to improve the strength and hardness of the ornamental facing layer 14. Thus, the concrete product 10 resists damage at all times including during removal from the mold, during packing, during shipping, during installation, during handling of any type and following installation.

0027The present invention also provides a number of benefits during manufacturing. Specifically, it enables the use of cheaper raw materials for the concrete substrate layer 18. Accordingly, gray cement may be utilized instead of white cement if desired. This is possible because the aesthetics of the product 10 are captured in the functionally graded ornamental facing layer 14 and intermediate strengthening layer 16 and, therefore, it is not necessary to provide aesthetics to the concrete substrate layer 18. In addition, the presence of the intermediate strengthening layer 16 allows the use of stiffer concrete for the concrete substrate layer 18. The use of stiffer concrete generally results in sharper 90-degree corners for the product in accordance with manufacturer desires.

0028The following example is presented to further illustrate the invention, but it is not to be considered as limited thereto.

0029The foregoing description of a preferred embodiment of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally and equitably entitled,