Classifications

• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B24/00—Use of organic materials as active ingredients for mortars, concrete or artificial stone, e.g. plasticisers
  • C04B24/24—Macromolecular compounds
  • C04B24/38—Polysaccharides or derivatives thereof
  • C04B24/383—Cellulose or derivatives thereof
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
  • C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
  • C04B28/14—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing calcium sulfate cements
• • 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
  • E04C2/02—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials
  • E04C2/26—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials composed of materials covered by two or more of groups E04C2/04, E04C2/08, E04C2/10 or of materials covered by one of these groups with a material not specified in one of the groups
  • E04C2/284—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials composed of materials covered by two or more of groups E04C2/04, E04C2/08, E04C2/10 or of materials covered by one of these groups with a material not specified in one of the groups at least one of the materials being insulating
  • E04C2/296—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials composed of materials covered by two or more of groups E04C2/04, E04C2/08, E04C2/10 or of materials covered by one of these groups with a material not specified in one of the groups at least one of the materials being insulating composed of insulating material and non-metallic or unspecified sheet-material
• • 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
  • E04C2/34—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 composed of two or more spaced sheet-like parts
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
  • C04B2103/0045—Polymers chosen for their physico-chemical characteristics
  • C04B2103/0053—Water-soluble polymers
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
  • C04B2103/46—Water-loss or fluid-loss reducers, hygroscopic or hydrophilic agents, water retention agents
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
  • C04B2111/00612—Uses not provided for elsewhere in C04B2111/00 as one or more layers of a layered structure
  • C04B2111/0062—Gypsum-paper board like materials
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/10—Compositions or ingredients thereof characterised by the absence or the very low content of a specific material
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W30/00—Technologies for solid waste management
  • Y02W30/50—Reuse, recycling or recovery technologies
  • Y02W30/91—Use of waste materials as fillers for mortars or concrete

Definitions

• This invention is concerned with improvements in structural sandwich panels having a lightweight core.
• the invention is concerned particularly although not exclusively with structural sandwich panels having an improved bond strength between the core and the outer facing sheets and a process for the manufacture of such panels.
• United States Patent No 1333553 described a composite panel having a core of building plaster, saw dust, extract of cactus juice and heavy black molasses sandwiched between sheets of pasteboard. Reinforcement of the panel was achieved by incorporating into the core material longitudinally extending timber strips.
• British Patent No GB 1528816 describes a lightweight structural beam comprising a low density core, such as fibre-reinforced aerated concrete or bonded perlite or vermiculite, with corrugated metal reinforcing members extending longitudinally along opposed side edges of the core.
• United States Patent No 4351670 describes a cast building panel having a low density core comprising a cement matrix incorporating fragments of cured cellular concrete.
• the low density core material is described as being non-shrinking and possessing both high strength and favourable insulation qualities.
• United States Patents 4505449, 4303722, 4559263, 4617219, 4778718, 4894270, 4963408, 4050659, 4436274, 4876151 and 5209968 all describe composite structures having a low density core with fibre reinforced skins extending over opposite faces thereof.
• United States Patent 5387626 describes an additive combination for aqueous mineral building materials such as plaster, mortars, adhesive cements and fillers to improve the workability attributes for use with spray plastering machines and as cement based adhesives. Such attributes include structural stability, levelling, straightening, slurrying and smoothing.
• compositions comprised mixtures of water-soluble cellulose ethers, polyacrylamides alkali-nietal or ammonium salts of cross-linked ungrafted or starch grafted polyacrylates, starch ethers and condensation products based on arylsulfonic acids and formaldehyde in the form of alkali metal or ammonium salts thereof.
• International Publication WO 02/42064 describes a reinforced lightweight dimensionally stable panel having outer skins of plywood or oriented strand board and a core of calcium sulfate alpha hemihydrate, hydraulic cement, an active pozzolan, lime and a reinforcing of glass fibres and ceramic or polymeric micro-spheres.
• Australian Patent No 638567 describes a building panel having outer skins of fibre-reinforced cement, fibre-reinforced gypsum plaster or gypsum plaster sheets faced with paper or plywood and a lightweight inner core of foamed concrete, with or without a lightweight aggregate such as polystyrene beads, etc.
• the panels are reinforced by attaching metal strips to the inner faces of the outer skins by adhesive.
• a major problem associated with prior art sandwich or composite panels is the ability to obtain a high strength bond between the core material, particularly a relatively low strength lightweight core material, and the outer skins.
• the inner core effectively does no work other than to act as a spacer for the outer skins which have flexural, compressive and tensile strength properties appropriate for a chosen application. If, when a load is applied to such a structural panel, one or both of the outer skins begins to delaminate from the core, a fairly catastrophic failure of the panel under load is a common occurrence.
• Australian Patent No 752467 sought to address the problem of limited bond strength between a lightweight cementitious core and fibre-reinforced cement sheets in a structural panel.
• the panel is located in a mould or press while powdered aluminium reacted with a lime-containing cement slurry to produce fine bubbles of hydrogen gas.
• the internal pressure generated in the core within the closed mould forced cement particles into intimate contact with the porous fibre reinforced cement facing sheets to improve the bond strength between the facing sheets and the ultimately cured core.
• porous or water absorbent facing panels such as fibre- reinforced cement or plywood
• the use of porous or water absorbent facing panels has imposed a limitation on the ultimate strength of the panel due to the tendency of water in the cementitious mix to migrate into the water permeable facing sheets whereby at the core/facing sheet interlace, cement particles are deprived of water otherwise required for hydration.
• the poorly hydrated cement particles were quickly immobilized in the layer of slurry adjacent the surface of the facing sheet and in the absence of complete and timely hydration of the cement particles, the physical/chemical bond between the core and the facing sheets was compromised, thus diminishing the strength of the panel.
• Australian Patent No 638567 sought to address this problem by effectively increasing the surface area of the facing sheets by forming grooves therein, while Australian Patent No 752467 sought to create a more intimate contact of cement particles with the facing sheet interface by internally pressurizing the cementitious slurry with a chemically generated gas.
• Air entrainment agents typically fatty acid sulphonate surfactants
• a special mixer designed to fold air into the slurry. Entrained air bubbles, apart from reducing the density of the cementitious matrix, improves the workability of the liquid slurry.
• a water : cement ratio as close to that theoretically required to hydrate the cement particles fully, but without surplus water which can reduce the strength of the cementitious mix.
• the ideal water : cement ratio is about 36 parts by weight of water to 100 parts by weight of cement powder. At this ratio however, the slurry is very viscous, difficult to mix thoroughly and difficult to pour.
• a plasticizer is added to the cementitious mix at a concentration of about 2% by weight of the mix. Where pozzolanic fly ash and lime are incorporated in the mix, a super-plasticizer is often used.
• the typical dosage of a plasticizer is from 200-450 ml per 100 Kg of cement powder while for a super-plasticizer, the dosage is from 750 ml to 2500 ml per 100 Kg of cement powder.
• Aerating agents and many of the plasticizers or super-plasticizers exhibit strong surfactant properties which are used to advantage in dispersion of cement powders and water distribution through a cement slurry.
• Surfactant compounds are relatively stable and remain dispersed throughout a panel core such that in the presence of any moisture, water is readily drawn into the porous cementitious core material.
• plasticizers or super-plasticizers are utilized in a cementitious slurry, they permit a reduction in the amount of water required to fully hydrate the cement particles and still permit flowability.
• any surfactant composition is present whether as an aerating agent or a plasticizer, the rate and extent of absorption of water into the facing sheets is increased, further diminishing the ultimate bond strength. It is therefore an aim of the present invention to overcome or alleviate at least some of the problems associated with the manufacture of structural building panels having a lightweight cementitious core and facing sheets on opposite faces thereof, or otherwise to provide users with a convenient choice.
• a method for the manufacture of a structural building panel comprising the steps of: locating in a mould, spaced facing sheets to form a cavity therebetween; introducing into the cavity a flowable cementitious core material to form, when cured, a lightweight panel core, the method characterized in that the flowable cementitious core material includes at least a partially water-soluble cellulosic polymer adapted to retain moisture in the cementitious core material in a region adjacent inner surfaces of the facing sheets to improve a bond between the core and the facing sheets by controlling the rate of hydration of cement particles in the region.
• the cementitious core material may comprise cement powder, for example
• the cementitious core material may further comprise a low density particulate filler.
• the low density particulate filler may have a density of between about 0.01 g/cm 3 and 4.0 g/cm 3 , or between about 0.1 g/cm 3 and 3.5 g/cm 3 , or between about 0.1 g/cm 3 and 3.0 g/cm 3 , or between about 0.1 g/cm 3 and 2.5 g/cm 3 , or between about 0.1 g/cm 3 and 2.0 g/cm 3 , or between about 0.1 g/cm 3 and 1.5 g/cm 3 , or between about 0.1 g/cm 3 and 1 g/cm 3 , or between about 0.2 g/cm 3 and 0.9 g/cm 3 , or below 1.5 g/cm 3 , or below 1.4 g/cm 3 , or below 1.3 g/cm 3 , or below 1.2 g/cm 3 , or
• the low density particulate filler may be, but is not limited to, expanded plastic material, expanded polystyrene beads, chopped expanded polystyrene, exfoliated vermiculite, perlite of micaceous aggregates, organically derived fillers such as rice and wheat husks, cellulose fibres, shredded paper, ceramic, vitreous or polymeric micro- spheres, pumice, expanded clay, expanded shale, polyvinyl chloride, polystyrene vinyl acetate, polyurethane, blast furnace slag, ceramic beads, glass beads, silicate beads and crushed cured porous cement mortar, or combinations thereof.
• expanded plastic material expanded polystyrene beads, chopped expanded polystyrene, exfoliated vermiculite, perlite of micaceous aggregates
• organically derived fillers such as rice and wheat husks, cellulose fibres, shredded paper, ceramic, vitreous or polymeric micro- spheres, pumice, expanded clay, expanded shale, polyvin
• the cementitious core material may consist essentially of cement powder, a low density particulate filler and a partially water-soluble cellulosic polymer. 5
• the cementitious core material may be other than a gypsum-based material.
• the cementitious core material may not contain primarily gypsum.
• the cementitious core material may comprise gypsum in an amount of no more than 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 8%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1% or 0.01% by weight of the cementitious core material. o
• the cementitious core material may not include gypsum.
• the cementitious core material may riot include a retardant or a dispersant.
• the cementitious core material may not include a plasticizer or super-plasticizer.
• the cementitious core material may not include a surfactant or an air-entraining or aerating agent. 5
• the cementitious core material may have a density of less then 0.45 g/cm 3 .
• the method of the first aspect may not include the step of aerating the flowable cementitious core material.
• the cellulosic polymer may comprise a non-ionic modified cellulose ether selected from the group consisting of: methyl cellulose, methylhydroxyethyl cellulose,o methylhydroxypropyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, ethylhydroxyethyl cellulose, methylethylhydroxyethyl cellulose, butylglycidylether- hydroxyethyl cellulose, laurylglycidylether-hydroxyethyl cellulose, carboxymethylated- methylhydroxyethyl cellulose, sodium carboxymethyl cellulose or mixtures thereof.
• a non-ionic modified cellulose ether selected from the group consisting of: methyl cellulose, methylhydroxyethyl cellulose,o methylhydroxypropyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, ethylhydroxyethyl cellulose, methylethylhydroxyethyl cellulose, butyl
• the cellulosic polymer may be of the following formula:
• the cellulosic polymer may be included in the cementitious core material in a ratio of from about 0.01 % to 5%, or about 0.01% to 4%, or about 0.01% to 3%, or about 0.01 to 2%, or about 0.01% to 1.5%, or about 0.01% to 1.25%, or about 0.01% to 1%, or 5 between about 0.02% to 1%, or about 0.02% to 0.9%, or about 0.04% to 0.8%, or about 0.05% to 0.7%, or about 0.05% to 0.6%, or about 0.05% to 0.5%, or about 0.06% to about 0.4%, or about 0.08% to 0.25% w/w of the cement powder.
• the cellulosic polymer may be included in the cementitious core material in the ratio of from about 0.05% to 0.4%, or about 0.05% to 0.3%, or about 0.05% to 0.25%, or0 about 0.05% to 0.2%, or between about 0.1 % to 0.2% w/w of the cement powder.
• the facing sheets may be selected from fibre reinforced cement sheets, plywood, PVA coated metal, plywood/metal laminates, fibre reinforced gypsum, paper faced gypsum panels or the like.
• a normally inner surface of the facing sheets, in use, bonded to the5 cementitious core is textured to enhance a bond between the facing sheets and the cementitious core.
• the inner surface of the facing sheets may include a plurality of ribs separated by channels.
• the cementitious material ⁇ may be aerated by air entrainment during mixing of the cementitious slurry and/or by chemical gas generation during curing of the cementitious slurry between the facing sheets. Conveniently however, this step can be omitted in the method of the first aspect.
• a pozzolan such as fly ash may also be incorporated into the cementitious slurry.
• a structural building panel comprising: spaced facing sheets having located therebetween and bonded thereto a lightweight cementitious core including a low density particulate filler and a bond 5 enhancing agent in the form of at least a partially water soluble cellulosic polymer, the at least partially water soluble cellulosic polymer being adapted, in use, to retain moisture in the cementitious core material in a region adjacent inner surfaces of the facing sheets to improve a bond between the core and the facing sheets by controlling the rate of hydration of cement particles in the region.
• the cementitious core may comprise cement powder, for example Portland cement powder.
• the cementitious core may further comprise a low density particulate filler having a density of between about 0.01 g/cm 3 and 4:0 g/cm 3 , or between about 0.1 g/cm 3 and 3.5 g/cm 3 , or between about 0.1 g/cm 3 and 3.0 g/cm 3 , or between about 0.1 g/cm 3 and 2.5s g/cm 3 , or between about 0.1 g/cm 3 and 2.0 g/cm 3 , or between about 0.1 g/cm 3 and 1.5 g/cm 3 , or between about 0.1 g/cm 3 and 1 g/cm 3 , or between about 0.2 g/cm 3 and 0.9 g/cm 3 , or below 1.5 g/cm 3 , or below 1.4 g/cm 3 , or below 1.3 g/cm 3 , or below 1.2 g/cm 3 , or below 1.1 g/cm 3 ,
• the low density particulate filler may be, but is not limited to, expanded plastic material, expanded polystyrene beads, chopped expanded polystyrene, exfoliated vermiculite, perlite of micaceous aggregates, organically derived fillers such as rice and wheat husks, cellulose fibres, shredded paper, ceramic, vitreous or polymeric micro-5 spheres, pumice, expanded clay, expanded shale, polyvinyl chloride, polystyrene vinyl acetate, polyurethane, blast furnace slag, ceramic beads, glass beads, silicate beads and crushed cured porous cement mortar, or combinations thereof.
• expanded plastic material expanded polystyrene beads, chopped expanded polystyrene, exfoliated vermiculite, perlite of micaceous aggregates
• organically derived fillers such as rice and wheat husks, cellulose fibres, shredded paper, ceramic, vitreous or polymeric micro-5 spheres, pumice, expanded clay, expanded shale, polyvin
• the cementitious core may consist essentially of cement powder, a low density particulate filler and a partially water-soluble cellulosic polymer.
• the cementitious core may be other than a gypsum-based material.
• the cementitious core may not include calcium sulfate.
• the cementitious core may not include a retardant or a dispersant.
• the cementitious core may not include a plasticizer or super-plasticizer.
• the cementitious core may not include a surfactant or an air-entraining or aerating agent.
• the cellulosic polymer may comprise a non-ionic modified cellulose ether selected from methyl cellulose, methylhydroxyethyl cellulose, methylhydroxypropyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, ethylhydroxyethyl cellulose, methylethylhydroxyethyl cellulose, butylglycidylether-hydroxyethyl cellulose, laurylglycidylether-hydroxyethyl cellulose, carboxymethylated-methylhydroxyethyl cellulose, sodium carboxymethyl cellulose or mixtures thereof.
• a non-ionic modified cellulose ether selected from methyl cellulose, methylhydroxyethyl cellulose, methylhydroxypropyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, ethylhydroxyethyl cellulose, methylethylhydroxyethyl cellulose, butylglycidylether-hydroxyethyl cellulose, la
• the cellulosic polymer may be of the following formula:
• R H, CH 3 , CH 3 -CH 2 , CH 3 -CH 2 -CH 2 or CH 2 CHOHCH 3 and n - 75-500
• the cellulosic polymer may be included in the cementitious core in a ratio of from about 0.01 % to 5%, or about 0.01% to 4%, or about 0.01% to 3%, or about 0.01 to 2%, or about 0.01% to 1.5%, or about 0.01% to 1.25%, or about 0.01% to 1%, or between about 0.02% to 1%, or about 0.02% to 0.9%, or about 0.04% to 0.8%, or about 0.05% to 0.7%, or about 0.05% to 0.6%, or about 0.05% to 0.5%, or about 0.06% to about 0.4%, or about 0.08% to 0.25% w/w of the cement powder.
• the cellulosic polymer may be included in the cementitious core in the ratio of from about 0.05% to 0.4%, or about 0.05% to 0.3%, or about 0.05% to 0.25%, or about 0.05% to 0.2%, or between about 0.1 % to 0.2% w/w of the cement powder.
• the facing sheets may be selected from fibre reinforced cement sheets, plywood, PVA coated metal, plywood/metal laminates, fibre reinforced gypsum, paper faced gypsum panels or the like.
• the inner surface of the facing sheets may include a plurality of ribs separated by channels.
• the cementitious material may be aerated by air entrainment during mixing of the cementitious slurry and/or by chemical gas generation during curing of the cementitious slurry between the facing sheets.
• a pozzolan such as fly ash may also be incorporated into the cementitious slurry.
• FIG. 1 illustrates a moulding press for manufacture of building panels according to the invention
• FIG. 2 shows graphically axial compression tests performed on panels made in accordance with the invention
• FIG. 3 shows graphically shortening of specimens against compressive load
• FIGS. 4 and 5 show graphically the results of bending tests on specimens
• FIG. 6 shows graphically the results of a racking test.
• the term "improve" as used herein in relation to the bond between the cementitious core material and the facing sheets may mean that where a water-soluble cellulosic polymer is included in the cementitious core material, as compared to when such a polymer is absent, a superior bonding between the cementitious core material and the facing sheets is obtained.
• structural building panel may mean a panel adapted to be used as a load-bearing structure in a building, for example a house.
• the press 1 may comprise a series of modules 2 supported on a concrete base 3. The upper portions of respective modules are supported by a head frame 5 of which portion is shown. Head' frame 5 supports an elevated walkway 5a.
• Press module 2 comprises a robust frame with spaced fixed upright members 6 reinforced by a bracing structure 4 and spaced movable upright members 6a slidably mounted on base rails 6b. Located within module 2 are spaced metal mould frames 9 defining panel mould cavities 10 with contoured closure plates (not shown) supported on mould frames 9 to define side and base closures to the mould cavities.
• the contoured side plates are paired such that one has a longitudinally extending tongue projection and the other having a longitudinally extending groove to form respective groove and tongue formations on the opposite sides of a panel, these formations enabling interconnection of adjacent panels, in use.
• the side plates also include locating slots to locate the edges of the facing sheets to form sealed edges to the mould 9.
• the base ' plates are similarly contoured to form either a tongue like projection extending along the base of a resultant panel or alternatively a groove extending along the base.
• the base plates also include locating slots to locate the edges of facing panels to form a sealed interior cavity between the facing sheets located in respective slots of side and base plates within the mould cavity 10.
• threaded nuts 14 on the ends of shafts 12 are tightened to place the entire module under compression.
• reinforced mould top closures 11 each spanning five mould cavities 10 are frictionally engaged between the respective top edges of mould frames 9 and facing sheets (not shown) and the undersides of spaced longitudinal beams 7 to form a sealed top closure to each mould cavity 10.
• a flowable slurry of cementitious core material is introduced into each mould cavity via respective top openings and the core material is allowed to cure at least to a "green" state providing sufficient structural integrity to allow removal of the semi-cured panels from the press.
• a considerable amount of heat is built up in the module as the cementitious slurry undergoes an exothermic hydration reaction.
• This build up of heat in the panel cores is considered to cause at least a partial thermal expansion of the core material which is resisted by the side, base and top plates surrounding the cores and under compression from tensioned shafts 12. This is a possible explanation as to why there is no noticeable shrinkage of the core materials or the resultant panel thickness when the green panels are removed from the press 1.
• the panels are then allowed to cure at ambient temperature for several days or they may be more rapidly cured in an autoclave.
• top closures 11 are engaged against the tops of mould cavities 10 to prevent expansion of the core material therefrom.
• Building panels according to the invention typically will have a thickness of from 50 mm to 100 mm with facing sheets having a thickness of from 3 mm to 6 mm preferably 4.5 mm, depending upon the specific panel use. It should be understood however that these dimensions may be varied to suit particular applications.
• the inner face of the steel sheet may be coated with a water soluble PVA adhesive compound and/or the slurry mix may include PVA adhesive to aid in the bonding of the facing sheet to the core.
• low density particulate fillers including expanded polystyrene beads, chopped expanded polystyrene, exfoliated vermiculite, perlite of micaceous aggregates, organically derived fillers such as rice and wheat husks, cellulose fibres, shredded paper, ceramic or polymeric micro-spheres, or crushed aerated cement slurries. Whilst not necessary, the cementitious slurry may be aerated with a conventional aerating agent to produce a dispersion of fine air bubbles to reduce core density.
• the cementitious slurry may also include a pozzolan such as fly ash together with lime and, when lime is present, a quantity of aluminium powder may also be incorporated into the slurry to generate gas bubbles in the slurry during mixing and otherwise to create an internal pressure in the mould to enhance bond strength even further.
• a pozzolan such as fly ash together with lime and, when lime is present, a quantity of aluminium powder may also be incorporated into the slurry to generate gas bubbles in the slurry during mixing and otherwise to create an internal pressure in the mould to enhance bond strength even further.
• modified cellulosic ether composition to the slurry imparts a number of distinct unexpected benefits.
• the cellulosic composition functions almost as an internal lubricant in the slurry, little if any aerating agent is required if the slurry is to be aerated. Moreover, the internal lubrication effect obviates the need for plasticizers or super-plasticizers such that the incorporation of traditional surfactant compositions into the slurry is also avoided. This overcomes the problem of moisture "wicking" within the panel core due to the dispersed chemically stable surfactant.
• the residue of cellulosic material initially acts as a sealant to prevent moisture ingress but over a relatively short period of time, the cellulosic residue disappears due to degradation by micro-organisms and cellulose enzymes associated with naturally occurring bacteria and yeasts.
• a cementitious slurry was prepared as follows:
• Example 1 The slurry of Example 1 was then introduced into a mould frame as described generally with reference to the apparatus of FIG. 1.
• the mould frame was adapted to produce a 75 mm thick panel with facing sheets of 4.5 mm fibro-cement spaced within the mould frame.
• the wall panels are a sandwich consisting of outer layers of 4.5 mm fibre-cement sheet each side of a layer light concrete in which the coarsest aggregate consists of small styrene spheres.
• the panels tested in this programme of testing had an overall thickness of 75 mm, were 600 mm wide and of varying heights to three metres.
• a shallow tongue on one vertical edge engages a matching groove in the vertical edge of the abutting panel 1.4
• the panels are to be supported along their bottom edge on a concrete slab or floor and restrained against translation in plan.
• a suspended floor or roof is intended to be supported on the wall line formed by the top edges of the panels.
• the bending resistance of the panels was examined by applying bending action to a series of single-panel (600 wide x 75 mm thick x 3 m long) specimen arranged horizontally and supported over a span of 2.5 metres.
• a screw actuator and load cell were used to apply and quantify load to the outer quarter-points of the span as described in section 11 of ASTM E72. Net central deflection was obtained by subtracting any downward support deflection from that of. the mid-span of the loaded panel. Three replicates were tested. The load was increased to failure in bending.
• a second 90 x 45 radiata pine strip was attached as a ledger beside the top edge of the specimen using 100 x 4 mm hex- head screws at similar spacings to the bottom edge.
• the top ledger was also glued to the inner face of the panel assembly using the same construction adhesive as used in the joints.
• a bottom corner was restrained and the diagonally opposite top corner of the wall specimen felt a racking load applied by a hydraulic jack and measured by a load cell.
• the top surface adjacent to the load point was restrained against vertical movement by the use of a block acting against the top of the steel test chamber.
• deflection transducer signals were logged with that of the load cell as the load was increased to failure.
• One 3 m x 3 x wall specimen only was tested for racking.
• the resistance of the ledger was assessed by applying a perpendicular point load to the mid span of ledger orientated in the plane of the panel. A hydraulic ram was used for the force and a load cell measured the peak load only.
• the first two panel specimens tested remained unbroken under a maximum axial compression of 100 kN, the load limit of the apparatus. That apparatus was modified for a further test but no clear failure was observed at the new limit of 160 kN. While the third replicate specimen remained intact under a maximum load of 164 kN, FIG. 2 shows that the central horizontal deflection had increased to 8 mm - it is probably that a buckling failure would have been close. It is unlikely that the specimen would have endured axial forces significantly greater than the maximum of 164 kN applied during the test.
• FIG. 3 plots the vertical shortening of the wall specimens against axial compression load.
• Table 4.1 shows the ultimate loads and calculated ultimate bending moments for the bending and bending plus axial load tests of 600 wide x 75 mm thick panels loaded at outer quarter points and spanning 2.5 metres. The results suggest that the approximately 10 kN of axial load increased the bending capacity by approximately 10%. This may be attributed to a mild pre-stress effect applied by the axial load. The lowest bending moment sustained was 1.49 kN m. Table 4.1: Ultimate loads and calculated ultimate bending moments for the bending and bending plus axial load tests of 600 wide x 75 mm thick panels loaded at outer quarter points and spanning 2.5 metres
• FIGS. 4 and 5 show load deflection curves for the bending and bending plus axial tests. While there is a transducer problem evident in the first specimen, the curves show a linear response up to central deflections of about 12 mm with a loss of stiffness preceding failure at central deflections between 20 and 28 mm. No cracking was observed prior to failure.
• FIG. 6 shows a plot of racking load vs net deflection - while some loss of stiffness at peak load may be read from the curve, the effect is not conclusive and it is conceivable that a more uniformly loaded wall could resist greater racking loads.
• Table 4.2 shows the withdrawal loads perpendicular to the panel surface for a series of six tests.
• Table 4.5 shows the ultimate lateral loads required to cause failure of the bottom edge kerf.
• the material on each side of the kerf was tested (sides A and B). It can be seen in Specimen 2 that a strong result on one side is matched by a weaker result on the other, reflecting a slight deviation of the ken from the midline of the bottom edge.
• Bond strength is normally tested by determining peel strength between the core and the facing sheet in Kg/cm 2 . Typical results for prior art panels exhibit a peel strength of between 1.6 - 3.0 Kg/cm 2 with a clean separation between the facing sheet and the core material. In the present invention the bond strength or "peel" tests were not able to be measured as the core material failed before the facing sheet/core bond. The ultimate strength of the panels according to the invention were thus a function of core strength rather than bond strength as with prior art panels, A simple "rule of thumb” test to assess bond strength consisted of laying a 100 mm x 50 mm timber stud on a concrete surface and then dropping a panel, face down, across the timber stud.

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• 2007
  • 2007-09-24 CL CL2007002741A patent/CL2007002741A1/es unknown
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  • 2007-09-25 PE PE2007001296A patent/PE20081075A1/es not_active Application Discontinuation
  • 2007-09-25 AR ARP070104225 patent/AR062975A1/es unknown

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