Classifications

• • E—FIXED CONSTRUCTIONS
  • E04—BUILDING
  • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
  • E04C2/00—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels
  • E04C2/30—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by the shape or structure
  • E04C2/38—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by the shape or structure with attached ribs, flanges, or the like, e.g. framed panels
  • E04C2/382—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by the shape or structure with attached ribs, flanges, or the like, e.g. framed panels with a frame of concrete or other stone-like substance
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
  • B28B1/00—Producing shaped prefabricated articles from the material
  • B28B1/50—Producing shaped prefabricated articles from the material specially adapted for producing articles of expanded material, e.g. cellular concrete

Definitions

• the invention relates to cementitious-material- based non-wood products for use in construction and for use as substitutes for dimensional lumber or corresponding engineered wood products and in the same applications and dimensions as wood lumber products.
• U.S. Patent 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 provides that structural function. Because it is common practice to remove parts of the dimensional lumber for fitting and other purposes in wood-frame construction, any cutting of the casing in this product would compromise the structural integrity of the member .
• 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
• 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 4-in. 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 l/20th of conventional concrete) .
• U.S. Patent 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. Patent 5,002,620 does not provide the necessary structural strength to permit use of this product in the form of dimensional lumber and as a primary structural element.
• U.S. Patent 4,351,670 and U.S. Patent 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 invention is intended to introduce a new source of lightweight aggregate for concrete.
• U.S. Patent 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 a structural function in this invention.
• U.S. Patent 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. Patent 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.
• the invention includes a method for constructing buildings using cementitious-material-based non-wood construction products and buildings constructed from such cementitious-material-based non-wood construction products.
• the invention further includes a method for manufacturing high-performance fiber-reinforced cellular concrete (HPFRCC) products and the use of such products as replacements for conventional wood lumber construction products.
• HPFRCC high-performance fiber-reinforced cellular concrete
• the products of the invention have the necessary strength, durability, nailability, and sawability for direct substitution for dimensional wood lumber in wood-frame construction applications.
• the invention includes cement- based HPFRCC products for use in direct substitution of dimensional lumber such as 2x4's, 2x6's, 2xl0's, etc. which are typically used in wood-frame construction.
• the construction products embodying the invention have load capacities in flexure, compression, tension, and shear that can equal or exceed the corresponding base values for stud grade lumber commonly used in construction.
• the geometries of the developed products can be identical to the corresponding conventional wood products.
• the products embodying the invention can also be made in a variety of shapes and sizes other than dimensional lumber sizes and shapes. They are nailable using common nails, with nail pull-out capacities comparable to wood, and sawable using common hand saws or electric saws.
• the basic material used in the products has approximately half the specific weight of conventional concrete, with substantially increased toughness (energy absorption capability) and ductility (ability to stretch without rupture, or squeeze without disintegration) when compared to conventional concrete or wood.
• the product embodying the invention has excellent insulation properties, is not susceptible to long-term deterioration due to termites or other harmful parasites affecting timber products, does not suffer from common lumber imperfections such as knots, is fire resistant, is shatter (impact) resistant, and can be made in a variety of colors, lengths, and assemblies.
• the product also has the unique potential of maintaining and using conventional methods and equipment used for wood frame construction (walls, floors, decking, etc.) without the need to further jeopardize dwindling, environmentally-crucial global forest product or timber resources. It also offers options for pre-fabricated framing panels for assembly at the building site.
• Fig. 1 shows a wall frame system embodying the invention .
• Fig. 2 shows a schematic cross section of a 2x4 product illustrated in Fig. 1.
• Fig. 3 shows a floor system embodying the invention.
• Fig. 4 shows a roof truss assembly embodying the invention .
• Fig. 5 is a schematic of a method for manufacturing high performance fiber reinforced cellular concrete embodying the invention.
• Fig. 1 illustrates a frame assembly 10 for use as a structural component of a building, such as a wall.
• the frame assembly 10 includes a plurality of studs 22 that are spaced-apart and fastened to a sole plate 20 by nailing or by the use of threaded fasteners such as screws or bolts at the stud bottom ends 32.
• the sole plate 20 is horizontally oriented, and the studs 22 are vertically oriented.
• a top plate 24 is fastened in the same manner to the stud top ends 30 of studs 22.
• the top plate 24 is horizontally oriented, and parallel to the sole plate 20. All studs 22, the sole plate 20, and the top plate 24 are made from high performance fiber-reinforced cellular concrete
• insulation 26 can be installed between the studs 22, and wallboard 28 can be applied to the frame assembly 10 using the same techniques as are used for wood lumber wall assemblies.
• Fig. 2 illustrates a schematic cross-section of a piece of dimensional lumber formed from HPFRCC, such as a 2x4 that would be used to construct the frame assembly 10 of Fig. 1.
• the cross-section shows a random distribution of voids 40 formed in the concrete.
• the cross-section also shows the randomly oriented and randomly distributed fibers 42 in the concrete.
• Fig. 3 illustrates a frame assembly for use as a structural component of a building, such as a floor.
• the frame assembly includes a plurality of joists 52 that are spaced-apart and parallel and fastened to end plates 50 by nailing or by the use of threaded fasteners such as screws or bolts at both ends of joists 52.
• Both end plates 50 and all of the joists 52 are horizontally oriented, with the two end plates 50 parallel to each other and the joists 52 oriented perpendicularly to both end plates 50.
• the joists 52 and end plates 50 are nailed together in the same way as wood lumber members are nailed together. All joists 52 and both end plates 50 are made from HPFRCC, which will be discussed in more detail below.
• Fig. 4 illustrates a frame assembly for use as a structural component of a building, such as a roof truss 60.
• the frame assembly includes a lower chord 62 that forms the base for the roof truss 60. With the lower chord 62, the two upper chords 64 form a generally A- shaped assembly. Connecting members 66 are disposed between and fastened to the lower chord 62 and the upper chords 64 to provide additional structural strength.
• the lower chord 62, upper chords 64, and connecting members 66 are fastened by nailing or by the use of threaded fasteners such as screws or bolts. Additionally, all joints are reinforced using plate- type gussets 68.
• the lower chord 62, upper chords 64, and connecting members 66 are made from HPFRCC, which will be discussed in more detail below. In one embodiment of the invention, the lower chord 62, upper chords 64, and connecting members 66 are nailed together in the same way as wood lumber members are nailed together.
• HPFRCC dimensional lumber members and the methods disclosed herein may be used in the fabrication of pallets, fencing, decking, cribbing, railroad ties, shelving, and any other products that can be fabricated from wood lumber.
• Fig. 5 illustrates a process for manufacturing lumber products from HPFRCC.
• the following components are mixed in a tank 80 containing a high-speed mixer 82.
• Type I cement can be used. However, other cement types can also be used to achieve particular properties.
• Fly ash 86 - Fly ash is a waste product (or byproduct) resulting from the burning of coal in power plants. It has cementitious properties, but is lighter than cement. Class F Fly ash is used. However, other types of fly ash and other pozzolans (such as silica fume) can also be used separately or in combination with each other.
• Fiber 90 Many types of synthetic and natural fibers for use in concrete are commercially available (carbon, polypropylene, alkali-resistant glass, cellulose, nylon, aramid, acrylic, polyethylene, etc.) and can be used in this application individually or in combination with other fibers.
• the type and amount of different fibers 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, multifilament, and fibrillated fibers are commercially available.
• Superplasticizer 92 A high range water-reducing admixture or superplasticizer 92 (meeting ASTM C494 F&G requirements) is used to improve workability of the mix.
• Aerating or foaming compound 94 Aluminum powder is used to aerate the mixture. The fineness of powder should be appropriate for production of cellular concrete. Foams or other compounds capable of introducing gas bubbles in concrete can be used in lieu of aluminum powder.
• Color pigments 96 if a colored product is desired A large selection of color pigments is commercially available from suppliers such as Davis Colors of Los Angeles, CA. These pigments can be used to introduce the desired colors throughout the product.
• surface color can be applied at the end of production by immersion in a paint bath or by brushing.
• sealers can also be applied to the surface in this manner if desired, especially in outdoor applications.
• the mix design must consider the impact of different materials on the resulting properties of the product.
• sand or a variety of lightweight sands can also be used. However, the inclusion of sand will alter the resulting properties of HPFRCC lumber members including their compressive strength. If used, silica sand can reduce the working life of many conventional saw cutting blades.
• the mixing process involves mixing fly ash 86 and part of the water 88, and sand if used, followed by the introduction of cement 84 and color pigments 96 if used. Additional water 88 and superplasticizer 92 are added to achieve the desired workability. Then, fibers 90 are introduced and mixed thoroughly with a highspeed mixer 82 while the remainder of the water 88 and superplasticizer 92 is introduced. Finally, aluminum powder 94 is added and mixed thoroughly with the highspeed mixer 82.
• HPFRCC mixture 98 is placed in forms 100 to a height below the final desired level.
• the action of the aluminum powder 94 raises the level of HPFRCC mixture 98 above the final desired level.
• HPFRCC mixture 98 is then removed 102, and the products are prepared for curing 104.
• 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 104 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.
• the products After an initial period of curing 104, the products will be demolded 106, cut to desired dimensions 108, and further cured 110. The products can then be shipped 112 as desired.
• a large block of HPFRCC 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.
• 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 or aerating agent is introduced into the mix, and the low-slump mix is fed into the extrusion process.
• fabrication plants that, based on individual building drawings, pre-fabricate wood-framed building panels including walls and floors that are then transported and erected at the site. Similar work can be performed with this set of products.
• fabrication and assembly can be either as individual members assembled together as done in the case of wood, or HPFRCC placement and fabrication for the entire framing panel can be made in one operation. Forming and wire cutting processes may be used. Also, additional internal and external reinforcement can be placed in the connection zones to further improve performance especially in areas with risk of significant earthquakes.
• the design load capacities for various grades and types of lumber products are provided in the "National Design Specification for Wood Construction and Supplement" published by the American Forest and Paper Association in Washington, D.C. These safe load capacities include inherent safety factors based on the likelihood of flaws or defects or construction deficiencies .
• the ACI 318 Code for reinforced concrete requires a load factor of 1.4 for dead load and 1.7 for live load with a reduction factor of 0.9 for flexure, 0.85 for shear, and 0.7 for compression. As an example, this results in an effective safety factor of 1.54 for dead load and 1.87 for live load (both for flexure) .
• the "Recommended Practice for Autoclaved Aerated Concrete” published by RILEM recommends a safety factor of 1.8 for flexure and 2.1 for compression in cellular concrete.
• RILEM the International Union of Testing and Research Laboratories for Materials and Structures, is located in France.
• HPFRCC the new class of products
• the safety factors apply to the ultimate strength of the product in compression, tension, flexure, and shear.
• a factor of safety of 1.25 against flexural cracking is proposed (similar to that existing for prestressed concrete in ACI 318) in addition to factors of safety of 1.8 and 2.1 against failure.
• Polypropylene Fiber 0.4%-3.2%
• Superplasticizer 0%-0.6%
• Aluminum Powder 0.012%-0.048%
• Color Pigment 0%-3.5%
• the above mixture will result in a minimum 28-day compressive strength of 2000 psi, minimum flexural strength of 1300 psi (based on moment strength and uncracked section properties) , a minimum first crack of 900 psi, a density of 75 lb. per cubic foot, and conventional nail pull-out capacities comparable to STUD grade lumber (per the Uniform Building Code tables) .
• the above mixture will meet or exceed the cellular concrete safety factors described above.
• the compressive strength of the HPFRCC is expected to increase substantially as the HPFRCC ages beyond 28 days. This is due to the presence of a large amount of fly ash in the mix.
• the quantities of cement and fibers can be reduced, while sand or lightweight sand can be used to replace part or all of the fly ash.
• the amount of aluminum powder can be increased. This will, however, reduce the compressive strength of the product.
• the advantages of the products embodying the invention can be summarized as follows. These products can be made in a variety of sizes and shapes including all dimensional lumber shapes. These products can be made in different colors and lengths. Wood lumber prices per board foot increase substantially with increased length and size. However, these products can be made in very long lengths or large cross sections without a major cost premium.
• These products can be made with sufficient strength parameters to serve as structural members and directly replace dimensional lumber in wall, floor, decking, and other applications. These products are nailable using common nails with nail pull-out capacities comparable to conventional lumber. These products are sawable using hand saws and a variety of electric saws commonly used for conventional lumber. They can also be drilled. These products have excellent insulation properties and have very low water permeabilities. The toughness and ductility of these products are better than conventional concrete or wood. These products do not suffer from common wood defects such as knots. Through proper production and quality control procedures, they can be made free of concrete defects such as honeycombs. These products are lightweight concrete with a maximum specific weight of approximately half the specific weight of conventional concrete. These products are not susceptible to attack by harmful insects or parasites such as termites.
• These products are fire resistant and shatter (impact) resistant. These products could make available highly- efficient wood-frame-type housing in areas of the world not possessing forest resources, such as desert areas. These lighter and more ductile structures offer a number of advantages including better resistance to seismic events. These products can positively impact the environment by substantially reducing dependence on the world' s environmentally-crucial forest resources while using a large quantity of waste products such as fly ash. These products offer new possibilities regarding pre-fabricated panels for assembly at the building site. These products allow new architectural design possibilities through the use of colors and the ability to create members with different surface finishes by using textured forms, for example.

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• 1999
  • 1999-05-12 AU AU39019/99A patent/AU3901999A/en not_active Abandoned
  • 1999-05-12 CA CA002331677A patent/CA2331677A1/en not_active Abandoned
  • 1999-05-12 WO PCT/US1999/010530 patent/WO1999058789A1/en not_active Application Discontinuation
  • 1999-05-12 EP EP99921936A patent/EP1102905A4/de not_active Withdrawn

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