Construction products and method of making same
A highly durable and easy to use prefabricated construction product is disclosed having a cellular concrete component sandwiched between two cement boards, wherein the cellular concrete component comprises cement, fly ash, an activating agent and water, and the cement boards comprise cement, fly ash, an activating agent, sand, silica fume, a water reducer agent, a reinforcing fiber, and water.
The present invention relates to concrete construction products that are structurally adjustable to suit many applications and to a method of making same.
II. BACKGROUND OF THE INVENTIONThe need for low cost prefabricated wall panels to suit varying structural requirements and varying geographical climates is substantial. Prefabrication of walling is well understood, the most common being made from reinforced concrete in the form of transportable panels. However in actual practice these types of walling systems although speeding up construction have failed to address the industry's need and in most cases have been proved to be more expensive than conventional construction, particularly in developing countries.
Over the years, many substitute building construction products have been brought into the market with varying degrees of success. New concepts have often required construction workers to learn new skills and use new forms of equipment to perform the construction work. These prior art concepts also affected conventional ways of handling other aspects of construction such as plumbing and electrical work. For example, replacing the wood frame wall concept with conventional concrete walls or Insulated Concrete Form walls requires construction workers skilled in concrete forming, placement, and curing, affects the way the electrical and plumbing work is performed, and results in a wall system far heavier than the corresponding wood frame system. Heavier building elements result in higher inertia forces during earthquakes.
Walls built with conventional cellular concrete blocks or panels are lighter, but have very low compressive strengths. Because of their brittleness, their response to lateral loading caused by earthquakes in seismic zones or caused by hurricanes or other strong winds is an area of major concern.
Steel studs have been developed and used to approximate wood frame construction. These hollow studs are made of cold-formed steel. They are generally not nailable, although metal screws are used. They are generally not sawable in the field and need to be pre-cut to exact lengths. The steel stud frames have pre-placed positions for the passage of plumbing or electrical hardware. Due to the high thermal conductivity of steel, ghost shadowing, which comprises the appearance of a shadow of the metal stud on the gypsum board wall, has also been a problem. Steel studs can also be susceptible to local or general buckling when subjected to extreme loads or heat.
U.S. Pat. No. 5,479,751 discloses a method and apparatus for fabrication of wood substitute products containing cement and synthetic resin. The disclosed product is described as having sawability and fastener-holding properties. The product includes an outermost casing (hollow tubular body) which is filled with cement and resin. Because the cement mixture inside the tube is not reinforced for tensile stresses, the casing does not provide sufficient structural function and any cutting of the casing in this product would compromise the structural integrity of the member.
The prior art also includes fiber reinforced concrete, and significant research has been performed particularly in the last decade on various applications of fiber reinforced concrete including the use of fiber reinforced cellular concrete building panels for construction of an envelope surrounding buildings for protection against hurricane-induced missiles. Fiber reinforced cellular concrete has included polypropylene fibers added to cellular concrete to produce four inch thick panels. Although this material exhibits improved toughness and ductility which are good properties against missile impact, its compressive strength is low (250 psi or approximately 1/20th of conventional concrete).
U.S. Pat. No. 5,002,620 discloses a laminated or sandwiched panel system in which layers of fiber reinforced concrete are cast against each other. The layers include a dense layer without air bubbles sandwiched with a lighter layer of cellular concrete. A vapor barrier is placed between the two mating layers. The dense layer of non-cellular material serves as the structural, load carrying element while the cellular layer provides insulation qualities. The fiber-reinforced cellular material discussed in U.S. Pat. No. 5,002,620 does not provide the necessary structural strength to permit use of this product as a primary structural element.
U.S. Pat. No. 4,351,670 and U.S. Pat. No. 4,465,719 disclose methods of making, and structural elements incorporating, a lightweight concrete. The lightweight aggregates for this concrete consist of broken-up pieces of cellular concrete that are coated with cement slurry. This material does not include fibers, and can be cast in a casing to form a composite building element. This patent introduces a new source of lightweight aggregate for concrete.
U.S. Pat. No. 5,685,124 discloses a folded plate panel using boards made of wood. Veneers are attached to one or both sides of the ridges of the folded plate. The hollow spaces thus created are filled with sound- and heat-insulating materials. Lightweight concrete and foamed concrete can be used as insulation filling the hollow spaces. The concrete is not intended to serve as a structural function in this invention.
U.S. Pat. No. 2,156,311 discloses a “cement-fibrous” lightweight material with fireproof and waterproof properties based on wood pulp and cement. The patent describes a manufacturing process involving filtering to remove water and roller forming of cement panels. This material is not an aerated cellular concrete.
U.S. Pat. No. 2,153,837 discloses the addition of a small amount of wood pulp to achieve uniformity in cellular concrete walls. The wood pulp is not intended to serve a structural function, but to ensure uniformity of the final product.
Aerated cellular concrete is a light-weight cement-based product that has been used in some concrete houses. A few commercial manufacturers produce cellular concrete blocks and panels in the United States. However, the structural systems used in such cases are typically based on load-bearing walls, which is a significant departure from framing systems used in wood houses. Cellular concrete is both sawable and nailable. However, special nails are generally recommended to provide nail pull-out capacities. The strength of common cellular concrete is relatively low. Because of its brittleness, fabrication of members such as 2×4's from cellular concrete is not feasible because they would easily break. In general, the ingredients of cellular concrete include Portland cement, silica sand, lime, water, and a foaming agent which is typically aluminum powder. Cellular concrete plants use autoclaves to cure the cast blocks.
The prior art has generally centered on production of either autoclave aerated cellular concrete (AAC) or variations thereof to produce a lightweight concrete with good strength for use as building blocks or panels. The light weight concrete may include a fiber reinforced cellular concrete using either aluminum or foam. AAC processes rely on expensive autoclave equipment to cure a mixture of cement, sand, lime and other materials that have been aerated by the reaction of powdered aluminum and high pH cement/lime. Various other processes have been proposed with systems based upon the use of aerating and other agents and casting forms to produce the desired shape of material or cutting the uncured material with wires. Most of these processes rely on a high percentage of cement in the mixture to achieve the desired product strength.
The AAC system is good for fire resistance and thermal protection, but much more expensive than other systems. This system has not been fully developed yet and has a few connection issues, it requires additional measure if more than one floor is required.
The relatively high cost of concrete systems is associated with the use and quantity required of Portland cement to make construction quality concrete. Portland cement accounts for approximately 75% of the total cost of structural concrete and therefore any reasonable cost reductions to be made in concrete costs must be associated with a significant reduction in cement content. These factors are further exacerbated by the weight of the prefabricated product being produced that create more stress around the lifting zones during de-moulding. The lighter the product, the less stress and the less cement hydration (hardening) is required.
Other prior art prefabricated construction products include Formless Concrete Construction (FCC), Insulated Concrete Forms (ICF), Structural Insulated Panels (SIP), and steel systems. These systems have several drawbacks with respect to structural integrity, economical consideration, and ease of installation.
Not addressed heretofore is the recognition of the need to use construction products that use available technology to create strong, stable, easy to install and economical buildings. Accordingly, there is a continued interest in the development of new construction products and new methods of making such products to address building safety, design and efficiency. The invention described herein addresses this and other needs by providing new construction products that balance the issues of design, safety, structural integrity and economy in the new buildings.
III. SUMMARY OF THE INVENTIONThe invention as described herein provides a prefabricated construction product comprising a cellular concrete component sandwiched between one or two cement boards, wherein the cellular concrete component comprises cement, fly ash, an activating agent and water, and the cement boards comprise cement, fly ash, an activating agent, sand, silica fume, a water reducer agent, a reinforcing fiber, and water. The activating agent comprises aerating agents, foaming agents, or both comprising metal agents, non-metal agents, surfactants, or a combination thereof.
The prefabricated construction products of the invention are made into external and internal wall systems, floor systems, ceiling systems and roof systems. The wall system comprises retainer walls, load-bearing walls, partition walls, external walls, internal walls, window walls, and tilt up walls, among others. The floor systems comprise floor pavers, roadways, parking lots, playing field, residential and industrial low rise and high rise floor systems, among others. The roof system comprises roof pavers, chimneys, internal and external roofs and ceilings. In one embodiment, the cellular concrete additionally comprises a reinforcing fiber. The reinforcing fiber comprises polypropylene, alkali-resistant glass, fiberglass, nylon, aramid, acrylic, polyethylene, polyvinyl alcohol, polyolefin, or a combination thereof.
In another embodiment, the cement boards comprise Portland cement in an amount of from about 18% to about 40%, the fly ash in an amount of from about 40% to about 50%, the silica fume in the amount of about 3% to about 7%, the activating agent in an amount of from about 0.012% to about 40%, the sand in an amount of from about 0% to about 40%, the reinforcing fiber in an amount of from about 0.4% to about 3.2%, and the water in the amount of from about 0.005% to about 60% weight based on a combined weight of non-aqueous components.
In yet another embodiment, the cement boards comprise the Portland cement in the amount of about 20%, the fly ash in the amount of about 40%, the silica fume in the amount of about 5%, the activating agent in the amount of about 30%, the sand in the amount of about 5%, polypropylene fibers in the amount of about 1 pound/M3 and two layers of fiberglass mesh, the water reducing agent comprises a super plasticizer in an amount of from about 0.02% to about 0.6%, and the water is in the amount of about 20% to about 27% weight based on a combined weight of non-aqueous components.
In yet another embodiment, the cellular concrete component comprises fly ash in the amount of about 60%, cement in the amount of about 15%, the activating agent in the amount of about 21%, and water in the amount of about 20% to about 60% weight based on a combined weight of non-aqueous components.
In another embodiment, the cellular concrete, the cement boards, or both contain additional materials to reduce cure time and increase product strength, such materials include, for example, lime, gypsum, plaster of Paris, sodium silicate, accelerators, and polymers in an amount of about trace to about 4% weight based on a combined weight of non-aqueous components.
In another embodiment, the cellular concrete is a fiber reinforced cellular concrete additionally comprising a reinforcing fiber in an amount of from about 0.001% to about 2.00%.
In yet another embodiment, there is provided a cementitous construction product comprising micronized polystyrene foam particles sandwiched between two cement boards, wherein the cement boards comprise cement, fly ash, an activating agent, sand, silica fume, a water reducing agent, a reinforcing fiber, and water.
In one embodiment, the micronizeed polystyrene foam particles have irregular surfaces and are made of a coarse powder having an average diameter f about 50 to 5000 microns.
In yet another embodiment, there is provided a construction product comprising a lower compartment of regular cement that is poured in the mould. This layer of cement also includes a fiberglass mesh inside. One or more layers of cellular concrete is then poured on the surface of the cement. A final layer of regular cement with fiberglass is then applied on the cellular concrete as the upper compartment of cement. The tickness of the lower and the upper cement layer may be the same or different and range from about 0.25, 0.5, 1, 1.5, 2, 2.5, to 3 inch or more. This embodiment, eliminates the need to create separate concrete boards and does not require amalgamating different parts of the cement boards together.
The construction products of the invention are environment friendly because they use substantial amounts of natural components with reduced construction time and waste.
Other preferred embodiments and aspects of the invention will be apparent to one of ordinary skill in the art in light of what is known in the art, in light of the following description of the invention, and in light of the claims.
IV. BRIEF DESCRIPTION OF THE DRAWINGS
The present invention relates to prefabricated construction products and method of making and using such products. The product described herein facilitate production of a prefabricated low cost concrete walling system that has a low overall Portland cement content and subsequently low materials cost and it is structurally adjustable to suit almost any application thus reducing waste. Additionally, the construction products of the invention significantly reduce the redundancy factor and weigh less than the prior art concrete construction products.
In one embodiment, the construction product of the invention is composed of three sections: a light synthetic or a natural material (e.g., cellular concrete, polystyrene, or both) in the inside and two cement board layers on the outside. These materials are not susceptible to temperature and environmental changes. Because the materials are so closely related to one another they will react uniformly to physical changes.
As used herein “construction products” includes internal and external walls (e.g., load bearing and non-loading walls, partition walls, etc) floors, roofs, and ceilings, among others.
As used herein “cement” refers to the class of material that bonds a concrete or other monolithic product. Hydraulic cement undergoes a hydration reaction in the presence of a sufficient quantity of water that produces the final hardened product.
As used herein “cement board” refers to a cementitious panel made of an aqueous cementitious mixture that is used protect the light weight material component of the inventive products from both the internal and the external sides.
As used herein “aqueous cementitious mixture” refers to any of a number of compositions comprising water, a cement material, and one or more chemical agents comprising (e.g., fillers, reinforcing fibers, activating agents, color, pesticidal agents, water repellents, fire repellents, aggregates, sodium silicate, and other industry accelerators and polymers, or a combination thereof), one or more masonary products (e.g., silica fumes, sand, fly ash, or other pozzolans or a combination thereof), and water reducers such as superplasticizer. The composition forms a slurry that hardens upon curing. Cement materials include hydraulic cements, gypsum, lime, plaster of Paris, and the like.
As used herein “reinforcing fibers” are broadly described herein to include polypropylene, alkali-resistant glass, cellulose, fiberglass, nylon, aramid, acrylic, polyethylene, polyvinyl alcohol, polyolefin, or a combination thereof.
As used herein “activating agents” include air entrainment agents, foaming agents such as ionic and non-ionic surfactants, aluminum powder, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkly phenyl ether sulfates or salts thereof, polyoxyethylene alkyl ether phosphates or polyoxyethylene alklyl phenyl ether phosphates or salts thereof, alkylbenzenesulfonic acids or salts thereof, alpha-olefinic-sulfonic acids or salts thereof, fatty acids or salts thereof, polyoxyethylene polyalcohol fatty acid esters, polyethylene glycol fatty acid esters, polyoxyethylene pentaerythryritol fatty acid esters and polyoxyethylene sorbitan fatty acid esters or salts thereof, ethylene glycol, hexylene glycol, ferrous sulfate heptahydrate, 2-butoxyethanol, vinsol resins, sodium lauryl sulfates, nonylphenol polyethylene glycol ether, or a combination thereof.
The construction products of the invention have a significant structural strength against earthquake and hurricane, have excellent insulation capacity (e.g., an excellent barrier to heat, cold, water, rain, air, sound, fire, wind), and a high load bearing capacity. These products are durable, economical, and can be used as a high-speed building alternative.
The use of the products of the invention in the construction industry does not require highly skilled workers and it has a fast work completion. The availability of the materials and their easy access facilitate the production of the construction products of the invention economically around the word.
Additionally, these products have a simple and user friendly electrical and plumbing connection methods that afford flexibility to plumbers or electricians by providing frames having pre-placed positions for the passage of plumbing or electrical hardware. All the required building construction products can be prefabricated and installed on location.
The construction products of the present invention have multiple applications in the building industry including, for example, residential high rise, residential low rise, commercial, and industrial. The construction products of the invention can also be successfully used as wall systems, floor systems, or roof systems in both internal and external applications. These products are used in several components of a building comprising, for example, roof, floor paver, chimney, roof paver, foundation wall, partition wall, wall under or above the window, tilt-up wall, load-bearing wall, drive way, ceilings, etc,
Small or large areas of concrete structures, such as roadways, parking lots and playing field bases can be monolithically cast with integral drainage elements using an especially formulated water-permeable concrete material having strength and durability comparable to conventional concrete in accordance with the invention. Such structures provide minimal interference with natural water flow patterns, optimal use of available land, sound proof, structurally sound, and highly durable floors.
In one embodiment, the construction product of the invention is a wall panel that is made up of two cement boards sandwiching a cellular concrete component in between. The cement boards are made of an aqueous cementitious material comprising cement, fly ash, silica fume, sand one or more activating agents, one or more fiber reinforcing materials that form a slurry that hardens upon curing. Cement materials include hydraulic cements, gypsum, lime, and the like.
In one embodiment, the cementitious material makes up, for example, about less than about 70% to about 80% of the total weight of the construction product, the water makes up approximately less than about 30% of the total weight of the construction product, the fiber makes up approximately less than about 4% of the total weight of the construction product, and the activating material makes up approximately less than about 1% of the total weight of the construction product. The construction product is formed in one, two or more separate processes or stages and performs as a homogenous or a heterogeneous product.
In another embodiment, the construction products of the invention comprise a prefabricated wall system comprising one, two or more cement boards and one or more cellular concrete sections. The cement boards comprises, by way of example and not limitation from about 20% to about 70% of fly ash, from about 10% to about 50% Portland Cement, from about 0.001% to about 2.00% reinforcing fibers, and from about %0.0001 to about %0.20 of activating agents. Portland Cement Type I can be used. However, other cement types can also be used to achieve particular properties.
In another embodiment, the construction products of the invention comprise the following constituents:
The foregoing total to approximately 100 wt % of the non-aqueous components of the mix. Water is added in an amount about 20% to about 60% weight based on the combined weight of non-aqueous components.
Additional reagent materials can be added to the mixture stated above if desired to promote various product qualities, including lime, gypsum, plaster of Paris, sodium silicate, and industry accelerators and polymers. Each of these additional reagent components may be added in an amount of about trace to about 2.0% wt, about 0.25% to about 4% of the total non-aqueous component portion of the mixture. The addition of these materials can reduce cure time and increase product strength.
The type and quantities of different materials, production processes, and curing methods affect the properties of the resulting product. The following ranges for the quantities of various products (as a percentage of total weight) can be used to achieve a wide range of properties for both structural and non-structural product grades:
- Portland Cement: 18%-40%
- Flyash (Class F): 0%-40%
- Sand: 0%-40%
- Water: 20%-27%
- Polypropylene Fiber (Monofilament): 0.4%-3.2%
- Superplasticizer: 0%-0.6%
- Aluminum Powder: 0.012%-0.048%
- Color Pigment: 0%-3.5%
The construction product of the present invention includes a light synthetic or natural material in between the two cement board. In one embodiment, the light material is a cellular concrete that can be fiber reinforced and made from a cementitious material, water, fiber, and an aerating material. The cellular concrete makes up approximately 18-40% of the total weight of the product.
In one embodiment the cellular concrete is a fiber reinforced cellular concrete mixture comprising the following materials:
The foregoing total to approximately 100 wt % of the non-aqueous components of the mix. Water is added in an amount about 20% to about 60% wt based on the combined weight of non-aqueous components.
As a means of reinforcing the final cured product, reinforcement fibers are added to the cementitious mixtures of the invention. Such fibers have a large length/diameter ratio so that a load is transferred across potential points of fracture. Typical preferred materials are fiberglass strands of approximately one to one and three fourths inches in length, although other fibrous materials can also be used. Other preferred fibers are commercially available from the Fibermesh company of Chatanooga, Tenn., and are comprised of polypropylene fiber.
Many types of fibers or reinforcing fibers for use in concrete are commercially available, such as for example, polypropylene, alkali-resistant glass, cellulose, nylon, aramid, acrylic, polyethylene, polyvinyl alcohol, polyolefin, or a combination thereof, among others.
The type and concentration of fiber depend on the desired strength properties (“structural” or “non-structural”) and the nailability of the product. The type of fiber used not only affects the amount of fiber required, but also impacts proportioning and choice of other mix ingredients. The ability to properly disperse the fibers within the mix is another important consideration. Due to cost, stiffness, and strength considerations, polypropylene fibers are used in the developed structural products. Monofilament and fibrillated fibers are commercially available. Reinforcing fibers can be used in the composition of the cement board, the cellular concrete, or both according to the invention.
Densities of hardened final products can vary from about 60 to 115 lb/ft3, about 70 to about 90 lb/ft3, with many products being about 80 lb/ft3.
Activating agents used within the scope of the invention comprise metal agents, non-metal agents, foaming agents such as surfactants (e.g., ionic surfactants, non-ionic surfactants), or a combination thereof, among others. Aluminum powder is also used to activate and/or aerate the mixture. The fineness of powder should be appropriate for production of cellular concrete. In one embodiment, the activating material is an aluminum power which makes up about 0.012% to about 0.048% of the total weight of the product. Foams or other compounds capable of introducing air bubbles in concrete can be used in lieu of aluminum powder.
In one embodiment, the activating agent is made up of fine grained aluminum metal (95%-325 mesh) in a paste form to coat the aluminum to prevent oxidation and preserve its reactivity. Aluminum pasts are available from Silberline, Mfg. Co., Tamaqua, Pa., under the “Flexcrete Aerating Agent” designation. This product includes fine aluminum particles (325 mesh) in a paste mixture with mineral spirits and diethylene glycol.
A host of different surfactants or foam builders can be used as part of the activator component. Generally, the surfactants are used when a high fly ash component is used. High amounts of carbon retard the reaction between aluminum and cement and make the product unstable through the initial curing stage, and product collapse can occur. Ethylene glycol may be used as one of the activator components. Additionally, the surfactant or foam builder may contain as a component either “Geofoam Liquid” or “Meacel 3532” both available from Engelhard. The former comprises hexylene glycol, ferrous sulfate heptahydrate, and 2-butoxyethanol. Other surfactants such as the alpha olefin sulfonates, vinsol resins (pinewood extracts), sodium lauryl sulfates, nonylphenol polyethylene glycol ether available from PB&S Chemical, Henderson, Ky., and condensation products of ethylene oxide and alkyl phenols can also be mentioned as exemplary components of the activating agent.
Also included within the scope of the invention are additional reagents that can be added to the activating agent including magnesium oxide and hydroxide reagents such as calcined Magnesite and Brucite, among others.
The activating agent is added at varying levels and amounts to produce different density building products and materials. For example, if lintel type material is desired, requiring somewhat greater strength, the density of the aerated concrete can be increased to 40-50 lbs/per cubic foot or greater. It is well known that the higher density of aerated concrete, the greater its compressive strength. Conversely, if light weight blocks and wall panels are desired, the activating agent can be varied to produce material in the 30-40 lbs/per cubic foot range.
Aerating or air entrainment compounds helps to create air cells or voids in a batch of concrete, which can help to maintain good workability of fresh concrete and also improve the durability to freezing and thawing of hardened concrete. AIR ENTRAINMENT.RTM. brand of air entrainment additive is the trademark of a proprietary high grade tree sap preparation that is preferentially included in some embodiments of the present invention, being used to entrap small air bubbles in cementitious compositions when desired. Other activating/aerating compounds include anionic surfactants such as polyoxyethylene alkyl ether sulfates or polyoxyethylene alkly phenyl ether sulfates or salts thereof, polyoxyethylene alkyl ether phosphates or polyoxyethylene alklyl phenyl ether phosphates or salts thereof, alkylbenzenesulfonic acids or salts thereof, alpha-olefinic-sulfonic acids or salts thereof, fatty acids or salts thereof, polyoxyethylene polyalcohol fatty acid esters, polyethylene glycol fatty acid esters, polyoxyethylene pentaerythryritol fatty acid esters and polyoxyethylene sorbitan fatty acid esters and the fatty acids or salts thereof.
In one embodiment, a lightweight concrete is prepared by, for example, inclusion of multitude of micro air bubbles in a cement-based mixture. In one embodiment, LITEBUILT® aerated lightweight concrete is created by inclusion of a multitude of micro air bubbles in a cement based mixture. This is achieved by mixing the concentrated LITEBUILT® Foaming Chemical with water and compressed air, generating foam therefrom. The LITEBUILT® Foam Generator is used to inject the foam directly into the concrete mixer which completes the process by mixing it with the sand/cement/water slurry. Most conventional ready mix or permanent concrete mixing facilities can be used for this task. LITEBUILT® aerated lightweight concrete behaves like ordinary dense weight concrete in most aspects, such as curing.
Micronized polymeric particles are an example of a weight saving agent that can be used in the product of the invention. The polymeric material may be included in the composition of the cement board, cellular concrete or both. Alternatively, the polymeric material is used in lieu of cellular concrete as the light weight material in between the two cement boards. These polymeric particles include, for example, polystyrene, polyester, polyethylene, polypropylene, acrylic, polyisocyanurate, polyacrylamide, polyacrylimide, mixed imide-amides arylamides, arylimides and the like. Also within the contemplation of the invention is the use of saw dust and wood pulp. The most preferred material is polystyrene.
Micronized polystyrene foam particulates are the result of a process of shredding virgin polystyrene foam, and give the final product its lightweight characteristics. In another embodiment, the micronized polystyrene foam particulates is made up of virgin polystyrene foam of approximately 1 to 5 lb/ft3 density that has been treated with a borate. The borate acts as a potent insect repellant, tending to keep vermin insects away from the rest of the structure of the building that incorporates such borate-containing cement compositions. This is to be distinguished from the use of cementitious compositions as a means of disposing of waste insecticides, including borate. Alternatively, a borate such as TIM-BOR.RTM. brand of borate available from U.S. Borax Co. can be added in powder form to the cementitious mixture.
Such foam block is then shredded to provide the micronized particles having irregular surfaces. A particularly well suited method of shredding is by running an electrified fine gauge wire through solid blocks of this foam, according to methods well known to those of ordinary skill in cutting and fabricating such polystyrene foam blocks. Alternatively, a wire brush can be used to brush against and abrade a solid foam block, thereby producing the desired small particulates of foam. This type of product is also generally available as a waste by-product at facilities that cut virgin polystyrene foam block. This process produces micronized foam particulates that can be characterized by sieve analysis in general conformance with ASTM C 136, entitled “Sieve Analysis of Fine and Coarse Aggregates”. Such method of analysis is suitable for particles of from 50 to 5,000 microns in size. A more preferred range of foam particle size is from 50-2000 microns, more preferably from 600-1200 microns. A typical sample yielded the following sieve analysis shown below:
The micronized polystyrene foam particulates can be characterized as a coarse to moderately coarse powder, having a median particle size of approximately 800 microns. Micronized foam of this type is available from the R-Control Co. of Denver, Colo., and other major cities or from Poudre Plastics of Fort Collins, Colo.
In another embodiment, a small amount of setting accelerator is also added to the cementitious material. At present, the preferred accelerator is sold under the trademark “Anti-Hydro” by Anti-Hydro Inc., Farmington, N.J. 08822. Reputedly, this product contains CaCl2. Also, a small amount of a thermal shrinkage control agent such as one or more of a variety of commercially available acrylic polymers may be added to the cementitious material to control thermal shrinkage during the initial cure of the mass. The acrylic products include “Duraweld” available from W. R. Grace, which is a polyvinylacetate polymer and vinylacetate dibutylmaleate copolymer dispersion in water.
Sand is frequently used to expand the volume of cementitious mixtures. Sand used in the cementitious mixtures of the present invention includes play sand from beach or river sources, and silica sand. Clay is a suitable alternative for sand in the mixtures of the invention. An especially preferred volume expansion material is expanded shale, clay and slate mix (ESCS). This material is a ceramic lightweight aggregate prepared by expanding select minerals in a ritary kiln at 1000 degrees celsius or more. This process results in a light weight, inert material comprised of a mix of oxides including SiO2, Al2 O3, Fe2 O3, CaO, MgO, K2O, N2O, SO3, P2 O5, TiO2, Mn2 O3, and CO2. ESCS is available through the Expanded Shale, Clay and Slate Institute, Salt Lake City, Utah, which makes a list available of distributors of this material throughout the U.S. The use of ESCS can replace sand in the cementitious mixtures of the invention and produce an especially light final product in concert with the foam particles described above.
Flyash is a waste product (or byproduct) resulting from the burning of coal in power plants. It has cementitious properties, but is lighter than cement. Fly ash can be used as a partial replacement for Portland cement in concrete construction, and it is generally accepted that the proportion of Portland cement replaced by the usual fly ash should not exceed about 20% to avoid significant reduction in the compressive strength or the resultant concrete. Fly ash is produced by the combustion of anthracite and bituminous coal in large industrial coal-fired boilers, especially for the steam generation of electricity that is suspended in the flue gases from such boilers and is separated there from by means such as electrostatic precipitation. The fly ash is an extremely finely divided material generally in the form of spherical bead-like particles, with at least 70% by weight passing a 200 mesh sieve and has a generally glassy state, resulting from fusion or sintering during combustion.
As recognized in the American Society of Testing Materials (ASTM) specification designation C618-85 entitled “Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Portland Cement Concrete”, fly ash is subdivided into two distinct classifications; namely, Class F and Class C. The definitions of these two classes are as follows: “Class F-Fly ash normally produced from burning antharacite or bituminous coal that meets the applicable requirements for this class as given herein. This class fly ash has pozzolanic properties. Class C-Fly ash normally produced from lignite or subbituminous coal that meets the applicable requirements for this class as given herein. This class of fly ash, in addition to having pozzolanic properties, also has some cementitious properties. Some Class C flyashes may contain lime contents higher than 10%.”
The reference to “pozzalanic properties” refers to the capability of certain mixtures, which are not in themselves cementitious, of undergoing a cementitious reaction when mixed with lime (calcium oxide) in the presence of water. Class F Fly-ashes can have from 4 to 9% calcium oxide contents, while Class C Fly-ashes can have from 30 to 60% calcium oxide contents. For this reason, Class C fly ash possesses direct cementitious properties as well as pozzolanic properties. Fly ash is readily available from local building products outlets. Fly ash that has been de-limed, is also readily commercially available from a variety of local sources. Fly ash components of the construction product of the invention is a C-type (“C-class”), an F-type (“F-class”), or both.
Also encompassed within the scope of the invention is the use of a water-reducing admixture or a superplasticizer to improve workability of the construction products. Color pigments are also used if desired. The type and concentration of these materials must be tailored according to the desired properties of the resulting concrete or cement. A large selection of color pigments is commercially available from suppliers such as Davis Colors of Los Angeles, Calif. These pigments can be used to introduce the desired colors throughout the product. Alternatively, surface color can be applied at the end of production by immersion in a paint bath or by brushing the products. Although the permeability of the developed products is very low, sealers can also be applied to the surface in this manner if desired, especially in outdoor applications.
The mixing process involves, for example, mixing flyash and part of the water, and sand if used, followed by the introduction of cement and color pigments if used. Additional water and superplasticizer are added to achieve the desired workability. Then, fibers are introduced and mixed thoroughly with a high-speed mixer while the remainder of the water and superplasticizer is introduced. Finally, aluminum powder is added and mixed thoroughly with the high-speed mixer.
In one embodiment, the construction product of the invention contains a class of low water weight cement mixtures that have from about 0.005 to about 5% v/v of water added to the final mix. Such low water compositions have been found to produce plastic cement mixtures that are readily processed through an extrusion die into a shape that needs no additional manipulation or molding. Also, the low water content compositions are well suited to being molded under high pressure.
The advantage of such high pressure molding operations is that after removing the pressure, the molded article can be ejected from the mold very quickly, usually after three to five minutes or so, thereby allowing the mold to be available for another cycle of molding another article. Ordinarily, when a plastic composition is being shaped in a mold, there is some period of time that the composition must remain in the mold until it has sufficiently hardened, a period known in the trade as ‘green time’. The longer the green time of a given composition being used to mold articles, the fewer times the mold itself can be cycled during a work day. Hydraulic cement undergoes a hydration reaction in the presence of a sufficient quantity of water that produces the final hardened product. The most preferred hydraulic cement for use in the invention is Portland cement. Various embodiments of the invention call for the addition of lime (calcium oxide) which is itself also a hydraulic cement.
The products embodying the invention can be made in a variety of shapes and sizes other than dimensional regular sizes and shapes. These products are available and usable at different lengths, widths, and thicknesses. For example, the cement boards are made of various sizes and dimensions including, by way of example and not limitation, 4, 5, 6, 7, 8, 9, 12, 15, 20, 30 feet or more in width and 8, 9, 10, 11, 12, 13, 14, 15, 20, 25, 30, or 40 feet or more in height depending on the special specification for a building. It is intended herein that by recitation of such specified ranges, the ranges recited also include all those specific integer amounts between the recited ranges. For example, in the range of from about 4 to 8, it is intended to also encompass 4.3×8.2, 4.5, 8.5, 4.7×, 8.7, etc, without actually reciting each specific range therewith.
The wall products of the present invention are made into load bearing walls, non-load bearing walls, or both. Non load bearing walls provide internal divisions to an internal space, e.g, simple room walling. Structural load bearing walls perform two functions, they support roof and upper floor loads and resist horizontal forces which is the structural function. In nearly every building, however, the requirements for the structural function as against the simple room walling function vary considerably.
An example of this would be a two storey house with a truss designed roof structure in which all the internal and external ground floor walls supporting the first floor and roof are obviously structural load bearing panels, however the internal walls on the upper floor are only semi structural non load bearing as they simply divide the rooms and the external walls on the upper floor are structural load bearing as they support the truss roof structure and resist wind forces. Accordingly, these walls perform different functions to a different degree and it is evident that there is always a requirement for variation by degree of structural and semi structural walling in each individual wall in almost every building structure and also a varying degree of structural requirement at every floor level depending on how much load is carried by each individual wall.
As structural safety is the more critical function of the design and manufacture of the walls, wall designers and engineers usually err on the side of making walls with a large degree of redundant strength for most structural walling. As it has not been economical to structurally design each wall panel, invariably the load-bearing walls and non-load bearing walls are used interchangeably. Strength and over design redundancy factors add to the cost of prefabrication to render it uneconomical in most general cases.
The wall systems of the present invention overcome the prior art problems by providing low cost prefabricated wall panels that are manufactured to suit varying structural requirements on an structurally graded basis.
The mixing process of different components of the construction products of the invention are well known to those of ordinary skill in the art. For example, in one embodiment, fly ash, cement, fiber and water are placed in a holding tank equipped with ‘wave breaker’ baffles located on the tank sides. The materials are mixed using a high-speed dispersion mixer with the appropriate horsepower and blade/tank diameter ratio. If desired, additional reagents such as lime, plaster of Paris and sodium silicate are also added to the mixture. The material is allowed to mix thoroughly for 2-5 minutes. Fiber materials are added and mixing is allowed to continue for an additional 2-5 minutes to completely disperse the fibers. The activating agents are added to the dispersion mixer and allowed to mix thoroughly with the other materials for an additional 1-4 minutes.
Following the mixing step, the activated mixture is placed into a mold for the aeration rise and curing. The transfer from the mixing tank to the mold should take place within about 5-6 minutes.
The present invention also provides methods of production of prefabricated construction product. Currently, there are many fabrication plants that, based on individual building drawings, prefabricate concrete and/or wood-framed building panels including walls and floors for transportation and erection at the site. Similar work can be performed with the construction products of the invention. In fact, fabrication and assembly can be either performed so that individual members assembled together, as done in the case of wood or concrete placement and fabrication for the entire framing panel, can be made in one operation. Also, additional internal and external reinforcement can be placed in the connection zones to further improve seismic resistance in areas with risk of significant earthquakes.
In one embodiment, the fabrication method comprises one, two or more separate processes. By separating the manufacturing process into two or more separate processes, the separate functions of the structural walling described above can be specifically addressed and designed individually to suit any requirement within the same building.
In one embodiment, the first stage of the process consists of manufacturing a plurality of walling units that can be made according to the invention described herein and it is strong enough to perform the walling function as specified. Encompassed within the scope of the invention are walling units having a hollow concrete block shape, made of Portland cement mixed with aggregates that are manufactured by an extrusion method similar to that used by a concrete block making machine. The hollow concrete is subsequently filled with light natural or synthetic materials, such as for example, cellular concrete or polystyrene.
In another prefabrication method, the concrete mixture is placed in forms to a height below the final desired level. The action of the aluminum powder raises the level of concrete mixture above the final desired level. The excess concrete mixture is then removed, and the products are prepared for curing. Autoclaving is not required, but accelerated curing procedures may be used. In general, moist curing or steam curing followed by air curing will be used. The method of curing will be based on a number of currently available methods for curing concrete, and will be dependent on the time requirements to achieve the necessary concrete properties, mainly compressive strength. After an initial period of curing, the products will be demolded, cut to desired dimensions, and further cured. The products can then be shipped as desired.
Other prefabrication and/or production alternatives exist. For example, a large block of concrete can be cast. Then, after the initial set is achieved, the block can be cut into the desired sizes using tensioned wires or high-temperature wires before proceeding with the curing processes. This process is generally used in the production of cellular concrete blocks. In another method, an extrusion process may be used for direct production of the desired sizes in lieu of the method of casting in forms. In this case, a foaming agent is introduced into the mix, and the low-slump mix is fed into the extrusion process.
The specific composition of construction products of the invention is well suited to the fabrication of molded construction materials. The composition is easier to pour than regular weight mixtures and exhibits greater strength. The compositions can be readily cast into molds according to methods well known to those of skill in the art for walls, floors and ceilings in virtually any three dimensional configuration desired. In the molding of roofing materials, the addition, or increase in the concentration, of an air entrainment agent makes the final product more water resistant.
The construction products of the invention can be used as walls, roofs, floors, sidewalks, driveways, molded chimney stacks or smoke stacks, furnaces, landscape block, retaining walls, pre-stressed concrete wall systems, tilt-up wall systems, i.e. where a wall component as poured on site and then tilted up when hardened; and as mason's mortar, among others.
A paver is a brick molded so as to be easily laid down upon a substantially horizontal roadbed or walkway surface to form an upper surface that can support foot or vehicular traffic.
A pre-stressed concrete wall system product is a molded, pre-formed panel or structural member made up of a concrete mixture in which embedded high-tensile steel is stretched, and then the stress is transferred to the concrete by bonding to the steel or by anchorages to the steel. Panels or structural members can be formed or molded into girders, load-bearing panels, floor sections, wall sections, and the like.
A tilt-up type of wall system product refers to a pre-molded or pre-cast concrete structural member that is poured while the mold is lying down, i.e. the intended vertical wall surface is laid down horizontally. Upon drying and curing, the horizontally-oriented wall or panel member is then tilted up until it is vertically oriented and moved into place as a constituent member of a wall system of a building. Such tilt-up wall components can form foundations below grade, or wall systems above grade.
This invention is further illustrated by the following example, which is not to be construed in any way as imposing limitations upon the scope thereof. On the contrary, it is to be clearly understood that resort may be had to various other embodiments, modifications, and equivalents thereof which, after reading the description herein, may suggest themselves to those skilled in the art without departing from the spirit of the present invention and/or the scope of the appended claims. The contents of all references, patents and published patent applications cited throughout this application are expressly incorporated herein by reference.
EXAMPLESIt will be understood by one of ordinary skill in the relevant arts that other suitable modifications and adaptations to the methods and applications described herein are readily apparent from the description of the invention contained herein in view of information known to the ordinarily skilled artisan, and may be made without departing from the scope of the invention or any embodiment thereof. Having now described the present invention in detail, the same will be more clearly understood by reference to the following example, which are included herewith for purposes of illustration only and are not intended to be limiting of the invention.
Example 1Effect of Initial Moisture Content and Type of Surface Finish Layers on the Energy Performance of a Residential House with Cellular Concrete Walls.
The hygrothermal behavior of an external wall made of two cement boards and one cellular concrete in the inside was numerically simulated for the first years of building use. A state-of-the art model applied for coupled heat, air, and moisture transfer in deforming porous building materials. Climatic data for a typical meteorological year for Toronto, Canada were applied for the definition of external boundary conditions. Four different cases for finish layers—interior and exterior wall surfaces, with and without a vapor-retardant paint—were considered. Based on the simulation results, space and time-averaged values of moisture content, thermal conductivity, apparent density, and specific heat of the cellular concrete layer were calculated for each month. These averaged material properties were used for a DOE-2.1E simulation of the whole building energy performance of a 143.1 m2 (1540 ft2) residential house for each month of the analyzed period. Additionally, monthly values were calculated for energy released or absorbed on the internal surface of the wall as a result of the condensation or evaporation process. These results have been used to approximate, for various types of cement boards used to protect the cellular concrete in the construction products. The results indicated low moisture content and elevated energy performance for the whole building during the first few years of its use. For example, the results indicated energy savings in the order of 50% to 80% reduction in the amount of the energy used for a comparable building having the same size in a similar location.
All references discussed herein are incorporated by reference. One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those inherent therein. The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.
Claims
1. A prefabricated construction product comprising a cellular concrete component sandwiched between two cement boards, wherein the cellular concrete component comprises cement, fly ash, an activating agent and water, and the cement boards comprise cement, fly ash, an activating agent, sand, silica fume, a water reducer agent, a reinforcing fiber, and water.
2. The prefabricated construction product of claim 1, wherein the activating agent comprises aerating agents, foaming agents, or both.
3. The prefabricated construction product of claim 2, wherein the activating agent comprises metal agents, non-metal agents, surfactants, or a combination thereof.
4. The prefabricated construction product of claim 3, wherein the activating agent comprises aluminum powder, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkly phenyl ether sulfates or salts thereof, polyoxyethylene alkyl ether phosphates or polyoxyethylene alklyl phenyl ether phosphates or salts thereof, alkylbenzenesulfonic acids or salts thereof, alpha-olefinic-sulfonic acids or salts thereof, fatty acids or salts thereof, polyoxyethylene polyalcohol fatty acid esters, polyethylene glycol fatty acid esters, polyoxyethylene pentaerythryritol fatty acid esters and polyoxyethylene sorbitan fatty acid esters or salts thereof, ethylene glycol, hexylene glycol, ferrous sulfate heptahydrate, 2-butoxyethanol, vinsol resins, sodium lauryl sulfates, nonylphenol polyethylene glycol ether, or a combination thereof.
5. The prefabricated construction product of claim 1, wherein the cellular concrete additionally comprises a reinforcing fiber.
6. The prefabricated construction product of claim 5, wherein the reinforcing fiber comprises polypropylene, alkali-resistant glass, fiberglass, nylon, aramid, acrylic, polyethylene, polyvinyl alcohol, polyolefin, or a combination thereof.
7. The prefabricated construction product of claim 1, wherein the cement boards comprise Portland cement in an amount of from about 18% to about 40%, the fly ash in an amount of from about 40% to about 50%, the silica fume in the amount of about 3% to about 7%, the activating agent in an amount of from about 0.012% to about 40%, the sand in an amount of from about 0% to about 40%, the reinforcing fiber in an amount of from about 0.4% to about 3.2%, and the water in the amount of from about 0.005% to about 60% weight based on a combined weight of non-aqueous components.
8. The prefabricated construction product of claim 7, wherein the cement boards comprise the Portland cement in the amount of about 20%, the fly ash in the amount of about 40%, the silica fume in the amount of about 5%, the activating agent in the amount of about 30%, the sand in the amount of about 5%, the reinforcing fiber comprises polypropylene in the amount of about 1 pound/M3 and two layers of fiberglass mesh, the water reducing agent comprises a super plasticizer in an amount of from about 0.02% to about 0.6%, and the water in the amount of about 20% to about 27% weight based on a combined weight of non-aqueous components.
9. The prefabricated construction product of claim 1, wherein the cellular concrete component comprises fly ash in the amount of about 60%, cement in the amount of about 15%, the activating agent in the amount of about 21%, and water in the amount of about 20% to about 60% weight based on a combined weight of non-aqueous components.
10. The prefabricated construction product of claim 1, wherein the cellular concrete, the cement boards, or both contain additional materials to reduce cure time and increase product strength, the materials comprising lime, gypsum, plaster of Paris, sodium silicate, accelerators, and polymers in an amount of about trace to about 4% weight based on a combined weight of non-aqueous components.
11. The prefabricated construction product of claim 1, wherein the cellular concrete is a fiber reinforced cellular concrete additionally comprising a reinforcing fiber in an amount of from about 0.001% to about 2.00%.
12. The prefabricated construction product of claim 1 made into external and internal wall systems, floor systems, ceiling systems and roof systems.
13. The prefabricated construction product of claim 13, wherein the wall system comprises retainer walls, load-bearing walls, partition walls, external walls, internal walls, window walls, and tilt up walls.
14. The prefabricated construction product of claim 13, wherein the floor systems comprise floor pavers, roadways, parking lots, playing field, residential and industrial low rise and high rise floor systems.
15. The prefabricated construction product of claim 12, wherein the roof system comprises floor systems comprise floor pavers, roadways, parking lots, playing field, residential and industrial floors.
16. A cementitous construction product comprising micronized polystyrene foam particles sandwiched between two cement boards, wherein the cement boards comprise cement, fly ash, an activating agent, sand, silica fume, a water reducer agent, a reinforcing fiber, and water.
17. A cementitous construction product of claim 16 wherein the micronizeed polystyrene foam particles have irregular surfaces.
18. The cementitious construction product of claim 16, wherein the micronized polystyrene foam particles are a coarse powder.
19. The cementitious construction product of claim 16, wherein the micronized polystyrene foam particles have an average diameter f about 50 to 5000 microns.
Type: Application
Filed: Sep 21, 2005
Publication Date: Mar 22, 2007
Inventor: Rafie Noushad (Richmond Hill)
Application Number: 11/231,506
International Classification: E04B 2/00 (20060101);
