Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
2000-10-30
2002-12-03
Wood, Elizabeth D. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S677000, C106S678000, C106S679000, C106S697000
Reexamination Certificate
active
06488762
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to compositions and a method of use of such compositions to produce cellular lightweight concrete suitable for structural applications, insulation, and as a lightweight aggregate.
BACKGROUND OF THE INVENTION
In general, there are two ways to achieve a low density concrete. Firstly, using a low density aggregate such as pumice or other lightweight rock. However, the use of lightweight aggregate material is not always feasible, since it is generally unavailable in many locations. The second way is to introduce gas or foam to the concrete mix to produce cellular lightweight concrete. According to ASTM specification, a cellular concrete is a lightweight product consisting of Portland cement, cement-silica, cement-pozzolan, lime-pozzolan, lime-silica pastes or pastes containing blends of these gradients and having homogeneous void or cell structure, attained with gas-forming chemicals of foaming agents. In cellular lightweight concrete, the density can be controlled by the introduction of gas or foam. The use of cellular concrete overcomes the supply problem associated with the use of lightweight aggregates, and further allows an increased degree of control of the density of the finished product. Thus, cellular concrete can be useful in floor fill and roof deck applications, providing insulation and a high degree of fire protection. It is generally unsuitable as a structural material because of shrinkage and cracking.
Cellular lightweight concrete has existed since the 1930's and is produced throughout the world. It is known for its properties including thermal and sound insulation, as well as being lightweight. Traditionally, cellular lightweight concrete is made with calcium containing materials and siliceous materials. Calcium containing materials may include Portland cement, granulated blast furnace slag, and lime; siliceous materials include fly ash and ground silica.
U.S. Pat. No. 5,002,620, discloses a method for a composite product which is formed from the casting of the lighter fraction over the heavier fraction to form a single sheet, with the lighter fractions of separate sheets being planed and bonded together with a vapor barrier therebetween to form blocks, wall panels, beams, and the like. The patent mentions that the concrete may be comprised of materials selected from the group including: Portland cement, suitable aggregates, fibrous reinforcing materials, ash from refuse-derived fuel, expanded silicate, water, sand, a preferred foaming agent and a source of compressed gas used in part to induce bubbles into the mix, and, a suitable vapor barrier/resin for use in bonding and moisture resistance. However, no details about those materials and proportions for each material were disclosed.
U.S. Pat. No. 5,183,505 discloses a cellular concrete mix with the addition of cementitious or non-cementitious fines. Cementitious fines consist of fly ash (Type F and C), slag cement and kiln dust. Non-cementitious fines selected from the group consisting of limestone, silica and granitic fines, and the amount by weight of said non-cementitious fines does not exceed about 50% of the combined weight of the cement and non-cementitious fines. The preferred ratio of cement to fines is 7:3, and the minimum amount of fines, either cementitious or non-cementitious, should not be below about 10% of the total weight of cement and fines.
U.S. Pat. No. 5,782,970 discloses a lightweight insulating concrete produced from a cement mix containing sawdust, diatomite, bentonite, and lime. The addition of rock salt and the entrainment of air bubbles result in a concrete with a high compressive strength, high thermal resistance (R) values (up to 30 to 40 times that of standard concrete), and excellent acoustical properties. The resulting insulating concrete is one-third the weight of standard concrete.
The use of recycled glass in glass manufacturing reduces energy consumption, raw materials use, and tear on machinery. However, not all used glass can be recycled into new product because of impurity, cost, or mixed colors. It is reported that the quantity of mixed waste glass has outstripped the quantity of color sorted glass. There is a need to develop applications for mixed waste glass. Use of recycled materials in construction applications is one of the most attractive options because of the large quantity, low quality requirements, and widespread sites of construction. The primary applications include a partial replacement for aggregate in asphalt concrete, as fine aggregate in unbonded base course, pipe bedding, landfill gas venting systems, and gravel backfill for distribution and sewer pipes. Ground glass possess pozzolanic reactivity, but cannot be used as a cement replacement in conventional concrete because of potential alkali-aggregate reaction. However, it can be used in the production of cellular lightweight concrete since alkali-aggregate reaction is not a concern.
SUMMARY AND OBJECT OF THE INVENTION
We have discovered that an economical and stable cellular concrete can be produced by the substitution of ground mixed waste glass for a portion of the cement in a cellular concrete mixture. The cellular concrete mixture containing ground glass are significantly more stable during foaming or aeration expansion process. It can be cured at either room or high temperatures to form hardened lightweight concrete products, which have a light-grey color and are more attractive than those containing coal fly ash.
More particularly, it is a purpose of this invention to provide a method of manufacturing cellular lightweight concrete using ground glass as a partial replacement for Portland cement in the mixtures.
A further objective of this invention is to be able to produce very stable cellular lightweight concrete mixtures during the foaming or aeration process.
A further objective of this invention is to be able to produce light color cellular lightweight concrete mixtures that can be easily tinted by adding proper pigments.
Yet another objective of this invention is to be able to provide applications which can use inexpensive recycled materials.
The aforementioned objectives are achieved by cellular lightweight concrete mixtures according to the present invention.
Briefly, therefore, the invention is directed to cellular lightweight concrete mixtures containing ground recycled waste glass that can be cured in steam at varying temperatures, and are characterized by excellent mechanical properties. The mixtures according to the present invention are composed of 3 to 70% cement, 3 to 70% ground glass, 0 to 60% cement substitute, 0 to 15% lime, up to 5% by weight fiber, 30 to 80% water, and up to 2% gas-forming or foaming agent. These materials are mixed to form a slurry, and poured into molds. The resulting products can either be cured at room or elevated temperatures.
With the forgoing and other objects, features and advantages of the invention that will become hereinafter apparent, the nature of the invention may be more clearly understood by reference to the following detailed description of presently preferred mechanical embodiments of the invention and the appended claims given for the purpose of disclosure.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention includes a mixture for producing cellular lightweight concrete. The mixture comprises cement, ground glass, cement substitute, lime, fiber, foaming agent and water. The invention also incorporates a method of making cellular lightweight concrete including mixing these materials in a mixer to form a thick, viscous slurry which will be foamed and cured at room or elevated temperatures.
The mixture may comprise approximately 3 to 70% by weight cement, 3 to 70% by weight ground glass, 3 to 60% by weight cement substitute, 0 to 15% by weight lime, 0 to 5% by weight fiber, 30 to 80% by weight water, and up to 2% by weight gas-forming or foaming agent. The mixing process can vary when gas-forming agents or foaming agents are used. When gas-forming agents such as aluminum, zinc, or magnesium are
Advanced Materials Technologies, LLC
Hodgson & Russ LLP
Wood Elizabeth D.
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