Patent Application
20070096353
1. Field of the Invention
This invention relates to the field of building materials. More specifically, the invention comprises a method for producing a simulated limestone finish on the surface of cast concrete tiles.
2. Description of the Related Art
Concrete has been used to cast functional and decorative building materials for many years. It may be used, as an example, to pour a monolithic floor slab. A finished surface can be created on such a slab, so that no further flooring material is needed.
Concrete is long-lasting and relatively inexpensive. One drawback, however, is its perceived lack of visual appeal. While some recent innovations in decorative surfaces have improved the appeal of concrete, it does not rival natural stone. Stone pavers or tiles display a natural variation in texture, luster, and color which many people find appealing. Most people prefer the look of natural stone. However, the price of stone—which can be ten times more expensive than concrete—often drives the consumer toward concrete. It would therefore be advantageous to provide a cast concrete product which mimics the desired surface look of natural stone.
The present invention comprises a new process for creating a decorative surface on a cast concrete tile. A mold is prepared by coating with mold release. An aggregate of water, coloring dye, sand, Portland cement, and pea gravel is pre-mixed. Dampened baking soda is sprinkled randomly into the bottom surface of the mold (which will bear against what becomes the top surface of the cast tile). The pre-mixed aggregate is then added to the mold. The aggregate is then screed and compressed in the mold to minimize voids. Aplastic cover is next added to reduce the moisture loss rate and increase the curing time.
Once the concrete is cured, the mold is separated into its component pieces and the cast concrete tile is removed. The upper surface of the cast tile will have been etched and otherwise transformed by the dampened baking soda, producing a surface texture similar to limestone.
Base 12 has two pin holes 30 which are adapted to receive pins 28 when the frame is placed on the base. As described above, corresponding holes 26 of upper tab 18 and lower tab 24 and corresponding holes 26 of upper tab 22 and lower tab 20 are aligned when half frame 14 and half frame 16 are joined to form a square. Pins 28 are then inserted through holes 26 and pin holes 30 in base 12.
The assembled mold is illustrated in
Concrete aggregate must then be made to produce the tiles. The aggregate can be any combination of concrete sand, gravel, cement, coloring agent and water. Those skilled in the art know that the precise formula can be varied to produce concrete with different appearances and properties. The aggregate is formed by mixing the aforementioned ingredients in a mixer. Additionally, the use of an ochre coloring agent is especially effective in creating stone-like coloration. A heterogenous coloration of the mixture can be produced by mixing the ingredients for three to five minutes, i.e., the coloring dye is unevenly distributed.
The mold is then filled as shown in
The aggregate is then allowed to cure as shown in
The resulting tile that is produced by this process is shown in
Different coloring agents can be used to mimic many variety of natural stone surfaces. 548 Ochre color, an effective coloring agent for producing a natural stone look, is commercially available from the New Riverside Ochre Company located in Cartersville, Ga. Other coloring agents can be used to imitate other naturally occurring stone colorations including dolphin grey, champagne, and rice white. Multiple coloring agents can even be used in the same batch to produce tiles with “swirls” of different colors. Furthermore, the degree of color variation can be controlled by adjusting the mixing time of the aggregate. A longer mixing time will result in a more homogenous coloration, and a shorter mixing time will result in greater color variation across the tile's surface.
The process can be automated as well. One example of an automated process utilizes multi-cavity automated machinery to produce the files with limited human assistance. An automated mixer can be used to prepare the aggregate, and a controller can be used to coordinate mixing and pouring time intervals. Using a conveyer belt or other means of locomotion, mold trays can be fed through various stations. First, the mold trays can be run through a station that sprays mold release. Second, the mold trays can be run through a station that randomly distributes baking soda across a two-dimensional field. The mold trays can then be sent to an injection site to be filled with aggregate. Finally, the trays can be circulated through an autoclave or other drying means to cure the concrete. A controller, like a programmable logic controller, can be used to coordinate the entire process.
Although the preceding descriptions contain significant detail they should not be viewed as limiting the invention but rather as providing examples of the preferred embodiments of the invention. As one example, many types and shapes of molds can be used to produce the concrete tiles. Accordingly, the scope of the invention should be determined by the following claims, rather than the examples given.
