COMPOSITE CEMENT BLOCK

Abstract: A dry mix suitable for making a building unit comprising, by dry weight, 20 to 50% sawdust, 30 to 50% cement and 5 to 20% lime (calcium oxide). In a preferred form, amounts of up to 1% glue may be also be added to the mix. The resulting building unit may be formed into building blocks of preferred sizes 600mm x 300mm x 100mm or 600mm x 200mm x 100mm. These building blocks when manufactured into their final form have improved fire insulation, acoustic insulation and compression properties.

Description: -1- Composite Cement Block TECHNICAL FIELD The present invention relates to a building composition, a building unit and a method of making same. The text of Australian provisional specification PH6196 and Australian provisional specification PH4396 is incorporated herein by cross-reference. BACKGROUND ART In the above referenced earlier provisional specifications prior art building block materials were discussed. In summary, prior art compositions and the building blocks resulting therefrom suffer from one of more of the following defects: Relatively complicated composition typically comprising many more than three components. Poor fire resistance or fire rating. Poor compression strength. Crack or crumble or other wise deteriorate relatively quickly upon exposure to the elements, particularly water. Will not reliably hold fixing devices such as screws or nails. Where such prior art compositions do not suffer from the above defects then they are typically relatively heavy. It is an object of the present invention to provide a building composition and method of making same which overcomes one or more of the defects of the prior art. The advantages to be gained by use of the selected composition of the present invention include one or more of the following: A relatively light block can be built from the composition. The resulting block has good compressive strength and good fire withstand capability. The resulting block will reliably hold screws, nails and the like. DISCLOSURE OF INVENTION In a preferred form there is provided a dry mix suitable for making a building unit, said mix comprising, by dry weight: sawdust in the range 20% - 50% cement in the range 30% - 50% lime in the range 5% - 20% In yet a further preferred form the mix comprises, by dry weight, about 50% sawdust, about 35% cement, and about 15% lime. In a further broad form there is provided a building unit manufactured from the above mix. In a preferred form enough dry mix to manufacture five blocks of dimension 600mm by 300mm by 100mm is combined with 25 litres of water, placed in block moulds and allowed to drain and set. In yet a further broad form there is provided a method of making a building unit comprising the steps of initially creating a dry mix as defined above, producing a wet mix by mixing said dry mix with water in the above specified proportions, pouring said wet mix immediately into « at least one mould, allowing said wet mix to drain and set in said at least one mould, and removing said building unit from said at least one mould upon setting of said wet mix. Preferably, a building unit and, specifically, a building block is made according to the above method. In a further broad form there is provided a mortar mix based on the above described dry mix BRIEF DESCRIPTION OF DRAWINGS Embodiments of the present invention and a method of making same will now be described with reference to the drawings in which:- Figure 1 is a perspective view of a block of a preferred embodiment according to Example 1 proposed using the moulds of Example 2; Figure 2 depicts a mould in an open state suitable for making a block of the preferred embodiment; Figure 3 depicts the mould of Figure 2 with tubular inserts inserted; Figure 4 depicts a group of moulds as arranged for mass production. MODES OF CARRYING OUR THE INVENTION An object of at least a preferred embodiment of the present invention is to produce a building composition, building unit and method of making same which possess as a common factor: - simplicity of ingredients; - cheap, readily available components; - production of a building unit or building composition having improved utility over gypsum/plaster blocks or concrete blocks; - ease of manufacture due to simplicity of components and favourable setting and curing characteristics. EXAMPLE 1 A building unit, in particular a building block having desirable properties and of dimensions 600mm x 200mm x 100mm is constructed as fol lows: A dry mix comprising by weight 50% sawdust 35% cement 15% 1 ime of sufficient quantity to fill five moulds of internal dimension 600mm x 200mm x 100mm is mixed with 25 litres of water to produce approximately 1 square metre of wall surface area of blocks (5 blocks) of dimension 600mm x 200mm x 100mm. The wet mix is poured into moulds of construction as depicted in Figs. 2 to 4 (except without the tubular inserts) of the internal dimension 600mm x 200mm x 100mm and allowed to set. Excess water mix is allowed to drain naturally frcm the moulds. Setting takes place within 24 hours whereupon the blocks can be released from the moulds. Preferably, the blocks are allowed to cure for a period of time, for example a few days, at room temperature. The resultant block is preferably of solid construction having no channels or voids within the structure. The composition together with the solid structure provides a block having the following characteristics as construed in terms used in the trade: the block will accept screws and nails; the block may be cut without crumbling or cracking; the block weighs under 10 kilograms; the block exhibits excellent acoustic, strength and fire rating properties - fire rating typically 4 hours - compression typically 20 MPa - acoustic insulation minimum 41 dBa. The block of this example is preferably for internal use. In a preferred form, 1% glue can be added to the dry weight composition. EXAMPLE 2 A building unit, in particular a building block having desirable properties and of dimension 600 mm x 300 mm x 100 mm is constructed as fol lows: a dry mix comprising sawdust 60%; cement 30%; lime 10% of sufficient quantity to fill five moulds of internal dimension 600 mm x 300 mm x 100 mm is mixed with 25 litres of water to produce approxi ately 1 square metre wall surface area of blocks (5 blocks ) of dimension 600 mm x 300 mm x 100mm. The wet mix is poured into moulds of construction as depicted in Figs. 2 to 4 of internal dimension 600 mm x 300 mm x 100 mm and allowed to set. Excess water mix is allowed to drain naturally from the moulds. Setting takes place within 24 hours whereupon the blocks can be released from the moulds. Preferably, the blocks are allowed to cure for a period of time, for example, a few days, at room temperature. The resultant block 1 is depicted in Fig. 1 having parallel, circular cross-section voids 2 extending therethrough as shown. The block so produced has the following characteristics as construed in terms used in the trade: the block will accept screws and nails without the need for any form of plug to be initially inserted. The screws and nails are retained in a manner similar to their retention in timber; the block may be cut without crumbling or cracking; the block weighs approximately 9 to 10 kgs which allows it to be lifted unaided by a building worker under current industrial regulations; the block is substantially crack resistant; the block is dimensionally stable under varying conditions of temperature, humidity and age; the block exhibits accoustic, strength and fire rating properties which render it suitable for use in domestic and commercial buildings according to current building regulations and market trends - refer elsewhere in the specification; the block is relatively quick and simple to produce. The materials from which the block is made are readily available and relatively cheap. The material composition of the dry mix can be varied over the following range (by dry weight): sawdust 50-70%; cement 40-20%; lime 10%. The lime composition should always be approximately 10% as indicated above. However, the sawdust and cement components can be interchanged within the ranges given providing their total comes to approximately 90% of the total dry mix weight. Reducing the cement component makes the resulting block somewhat more brittle and reduces its compressive strength. A variation of a few percent on either side of the above ranges should be allowable in practice and yet still provide a block with the characteristics described. Ambient conditions and the quality of the components may affect these ranges and, therefore, when employing a mix near the endpoints of the specified range trial and error experimentation is advisable to ensure that the required characteristics are indeed produced. Reduction of cement below the range specified creates a block with defects as previously outlined in respect of plaster blocks. Additionally, the mix of the above preferred embodiment of Example 1, due to its relatively fine structure and controlled and short time drying properties, makes it suitable to produce blocks in individual moulds in groups, each block having parallel apertures extending at least substantially the whole of the way through the block in one direction. These apertures may extend quite close to the edges of the block without lowering the structural strength characteristics of the block to unacceptably low levels. This is, in part, due to the fine structure of the block mix.

Claims: CLAIMS 1. A dry mix suitable for making a building unit, said mix comprising, by dry weight: sawdust in the range 20% - 50% cement in the range 30% - 50% lime in the range 5% - 20% 2. A mix suitable for making a building unit, said mix comprising, by dry weight, about 50% sawdust, about 35% cement and about 15% lime. 3. A building unit manufactured from the mix of claim 1 or claim 2. 4. A building unit according to claim 3 manufactured in solid block form of approximate dimension 600mm x 300mm x 100mm. 5. A building unit according to claim 3 manufactured in solid block form of approximate dimension 600mm x 200mm x 100mm. 6. A method of making a building unit comprising the steps of initially creating a dry mix as claimed in claim 1 or claim 2, producing a wet mix by mixing said dry mix with water, pouring said wet mix immediately into at least one mould, allowing said wet mix to drain and set in said at least one mould, and removing said building unit from said at least one mould upon setting of said wet mix. 7. The method of claim 6 wherein said wet mix is scaled proportionately on the basis approximately 25 litres of water together with said dry mix in sufficient quantity to manufacture 5 blocks of dimension 600mm x 300mm x 100mm. 8. The method of claim 6 wherein said wet mix is scaled proportionately on the basis approximately 25 litres of water together with said dry mix in sufficient quantity to manufacture 5 blocks of dimension 600mm x 200mm x 100mm. 9. A mortar mix comprising a sufficient quantity of water mixed together with the dry mix of claim 1 or claim 2. 10. The mix of claims 1, 2 or 9 further including approximately 1% by weight glue. 11. A block made from the mix of claim 10 of dimension 600mm x 200mm x 100mm.

Inventors: KRUSS LEON, KRUSS, LEON
Applicants: KRUSS LEON, KRUSS, LEON
Application year: 1987
Main classification: C04B18
IPC codes: B28B7, C04B28, E04B2, E04C1, E04C2