CA2108042A1

CA2108042A1 - Composite cement block

Info

Publication number: CA2108042A1
Application number: CA 2108042
Authority: CA
Inventors: Leon Kruss
Original assignee: Individual
Current assignee: ROSSETTO BRUNO ANGELO
Priority date: 1991-04-08
Filing date: 1992-03-17
Publication date: 1992-10-09
Also published as: AU7421491A; WO1992017416A1; JPH06506177A; EP0580613A1; EP0580613A4

Abstract

A building block composition, a building unit and a method of making same. A building block composition to the invention comprises by dry weight: sawdust (20-70 %), cement (20-50 %), plaster or lime (5-20 %). A building block is made from this composition by adding an appropriate amount of water and, in some embodiments, a predetermined amount of glue. In one form of the invention fresh sawdust is used.

Description

WO 92/17416 21 ~ ~J 0 12 PCI`/AU92/00114 COMPOSITE CEMENT BLOCK
BACKGROUND OF THE INVENTION
The present invention relates to a building block composition, a building unit and a method of making same.
Many attempts have been made to develop building compositions which provide desirable characteristics in, for example, building block form.
Desirably such characteristics are to be achieved at minimum cost.
Typically, minimum cost implies that the materials of the composition are readily available in large quantity.
With reference to building blocks the prior art includes the following:
U.S. 2899325 to Kranz details a block composition having desirable characteristics and including proportions of sawdust, sand, cement, gypsum, resin and water. The preferred proportions described therein suggest a dry mix composition by weight of approximately the following (converted from volumes specified):
sawdust 33%
sand 33%
cement 16%
burnt gypsum 16%
pine resin 1%
It will be noted that this composition includes a substantial proportion of a filler, namely sand.
The composition of this block, due particularly to the sand, makes it difficult to work and saw. Also nails and screws are not retained well in such a composition. Typically special plugs are required as an intermediary to hold them lnto the composltlon.
G.B. 1552226 to 5. Morris (Yeovll) Limited details a composition which includes as an essential lngredient pulverised bark. Again, a filler material or aggregate material such as limestone or clinker is specified.
The pulverised bark is stated to be that specifically available from softwood trees.
A preferred composition of this citation is (by volume) cement 5_50%
crush limestone aggregate 0-20%
- clinker breeze (having a cellular structure) 0-60%
pulverised bark 20-70%
In order to achieve lightness this structure relies upon a "cellular"

W O 92/17416 2 1 0 ~ ~ ~ 2 PCT/AU92/00114 structure generated by use of the clinker breeze and the pulverised bark.
A further known specification is Australian Patent Specification AU A 39887/8S to Kustra. A preferred composition of this disclosure is (by weight) plaster 35-65%
woodchips 15-40%
lime 10-25%
milk powder 0.5_3%
detergent 0.5-3%
animal glue 0.05%
Again, in this specification, numerous ingredients are used to achieve the desired effects. In particular, a substantial proportion of lime has been used.
The objects of the above specifications are variously stated to be production of a building composition and, in particular, a building block having at least some of the following characteristics:
good thermal insulation properties, good load bearing or structural strength properties, dimensional stability under varying conditions of moisture, time and temperature, cheap to construct, comprised of readily available materials, able to be worked - including cutting, sawing, driving in of nails or screws, convenient, quick and simple to manufacture, i.e. minimum setting, curing and aging times desired, complies with building and industrial regulations.
Additionally, there is known commercially in Australia the "Lok Block" (Trade Mark) and the "Brady Block" (Trade Mark). These blocks comprise substantially plaster and, optionally, fibreglass. These blocks are relatively expensive, relatively heavy, will not retain fixing devices such as nails or screws and have a strong tendency to chip and/or peel or are otherwise dimensionally unstable under high moisture conditions. Over time they have a tendency to crack.
However, the prior art compositions and the building blocks resulting therefrom suffer from one or more of the following defects:
Relatively complicated composition typically comprising many more than three components.
Poor fire resistance or fire rating.

WO 92/17416 21 0 $ 0 4 2 ` PCr/AU92/00114 . ~. , " ~
Poor compression strength.
Crack or crumble or otherwise 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.
Prior art building compositions have not utilised or recognised the advantages of using a high proportion of sawdust in the composition. Part of the reason for this appears to be that it has been thought that very high quantities of sawdust would lead to a degradation in brick characteristics.
Furthermore, in these days of high wage costs associated with constructional labour, it is desirable to provide a building unit which can be used to construct either inside or outside walls quickly and lS efficiently. Desirably, this is achieved by the use of building units in a block form. Preferably, the blocks are as large as possible to minimise the number of blocks required to create a wall. Size of block must however typically be traded off against the weight of the block. Industrial regulations typically specify the maximum weight that may be lifted by a worker in any one lift. Desirably blocks should be below this weight.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved building composition, building unit and method of making same which overcomes one or more of the defects of the prior art.
Accordingly, one aspect of the present invention provides a building block composition suitable for making a building unit, said composition comprising:
sawdust in the range 20-70%
cement in the range 20-50%
lime in the range 5-20%
In a preferred form the composition comprises, by dry weight, about 50% sawdust, about 35% cement, and about 15% lime.
In a further preferred form the composition comprises, by dry weight, about 60% sawdust, about 30% cement, and about 10% lime.
In a further broad form, the composition comprises, by dry weight, about 70% sawdust, about 20% cement and about 10% lime.
In yet a further preferred form the composition comprises, by dry weight, about 50% sawdust, about 40% cement, and about 10% lime.
In a further broad form there is provided a building unit W O 92/17416 ~ 0 4 ~ P ~ /AU92/00114 manufactured from the above composition.
In a preferred form enough dry composition to manufacture five blocks of dimension 600mm by 300mm by lOOmm 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 composition defined above, producing a wet mix by mixing said dry composition 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.
Preferably, a building unit and, specifically, a building block is made according to the above method.
In a second aspect of the present invention there is provided a building block composition comprising, by dry weight:
sawdust 20-70%
cement 20-50%
plaster 5-20%
Preferably, there is provided a building block made from the above composition, said composition in an unset state, further comprising 50 grams of glue and 10 litres of water per cubic metre of composition.
According to a further aspect of the present invention there is provided a lighweight building block comprising a mix whose dry weight composition is approximately 35% casting plaster, 45% type A Portland cement and 20% sawdust, said composition mixed with water and moulded and dried to form said lightweight building block, said block incorporating a plurality of substantially parallel perforations extending therethrough.
Preferably said plurality of substantially parallel perforations take the form of cylindrical channels.
In a further aspect of the present invention, there is provided a building composition comprising, by weight, between 60 and 70% sawdust, between 15 and 25% clay and approximately 15% cement.
In a further broad form there is provided a building composition comprising about 70% sawdust, about 10% clay, about 10% cement and about 10% lime.
Preferably, Eucalypt derived sawdust is used.
Preferably, the Eucalypt from which the sawdust is derived are one or more of Ironbark, Bluegum and Stringybark.
In yet a further broad form there is provided a method of making a building unit, comprising the steps of initially creating a dry composition WO 92/17416 21 0 ~ ~ ~ 2 PCI/AU92/00114 comprising by dry weight about 20-70% sawdust, 20-50% cement and 5-20%
plaster; producing a wet mix by mixing said dry composition with approximately 50 grams of glue and 10 litres of water per cubic metre of wet mix; pouring said wet mix immediately into at least one mould; allowing said wet mix to set in at least one mould; and removing said building unit from said at least one mould upon setting of said wet mix; said setting taking place over a relatively short period of time; said building unit produced by said method not requiring any further curing or aging before use.
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 compositions.
In a preferred form of the invention, fresh sawdust replaces sawdust in any of the above forms of the invention. Preferably also one or more of calcium chloride, copper sulfate, animal glue and powdered milk can be added to any of the forms of the invention.
BRIEF DESCRIPTION OF THE 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.
DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF 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.
A dry composition suitable to produce a block having at least some of the properties comprises the following components (by dry weight):
sawdust 20-70%

WO 92/17416 . ; .. .. PCr/AU92/00114 2108042 `

cement 20-50%
plaster 5-20%
A further preferred composition of a block is a dry weight mix of approximately 35% by weight casting plaster, 45% by weight of type A
Portland cement and 20% by weight sawdust. This composition is mixed together with approximately 20 litres of water per five blocks mix.
A block constructed according to the embodiment has been found in prototype experimental arrangements to be light and therefore easy to use.
The block has also been found to have admirable fire resistant properties.
The plaster composition in the dry weight mix may vary between 30%
and 40%. The cement composition in the dry weight mix may vary between 25%
and 70%. The sawdust may vary in the dry weight mix between 10% and 50Z.
Obviously the total for any one mix must equal 100%. The proportions given for the embodiment of the invention are the preferred proportions which have been found by experiment to provide the best compromise between weight, cost of construction and fire retardant capability.
A small proportion of lime may be added in certain circumstances.
However this is not required to produce a satisfactory block.
In a preferred embodiment, the invention for wood concrete uses only fresh sawdust. This is preferably only hard-wood sawdust such as turpentine, mahogany and hard varieties of eucalyptus. The sawdust should not be older than one month. Completely fresh sawdust possesses a number of chemical and mineral components in large concentrations and wood concrete can be produced from it without any additions. Wood concrete from fresh sawdust is also very light and strong and has considerable fire-resistant qualities and sound-insulating properties. The product is also excellent thermal insulation. Concrete produced from fresh sawdust, as the previous experiment has shown (durability test), is very durable and stable.
When stale sawdust is used to make wood concrete, it requires special treatment with chemical additives plus the addition of sand or other additives.
Wood concrete made without this additional treatment lacks durability and has reduced fire-resisting qualities and sound-insulating properties.
The ratio of sawdust to cement can be very high (70% sawdust, 30%
cement). Concrete with this high content of sawdust does not lose its fire resistance, its sound insulating properties or its durability.
Wood concrete with fresh sawdust does not have sand or other additives. This means that it can easily be sawn, nailed or sanded, in W O 92/17416 ;21Q~0~ PCT/AU92/00114 addition to possessing many other favourable properties required in the building industry. Wood concrete has high workability and represents a unique building material.
Further embodiments will now be described with reference to Examples.

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 follows:
a dry mix comprising sawdust 10 kgs;
cement 20 kgs;
casting plaster 13 kgs is mixed with 50 grams of pearl or animal glue and 10 litres of water to produce approximately 1 square metre wall surface area of blocks (5 blocks) of dimension 600 mm x 300 mm x 100 mm. 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. Setting takes place in approximately 20 minutes 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 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 acoustic, 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.

210~ 0 i 2 -8-Experimentation suggests that the block is sensitive to variations in its material composition as follows:
The experiment indicates that variations in the above proportions have the following effects. Increasing the amount of sawdust renders the block closer to the behaviour of ordinary timber at least in so far as the block's ability to accept and retain nails and screws is concerned. The upper and lower levels to the amount of sawdust given in the example is 10 kgs plus 5 kgs and -5 kgs respectively. The cement proportions may be reduced whilst at the same time making corresponding increases in the amount of casting plaster and vise versa. The effect of reduction in the proportion of casting plaster is to cause is to cause a longer drying time and produce a worse fire rating. Increasing amounts of casting plaster at the expense of cement do however render the block cheaper and lighter. The limits on the proportions of cement and casting plaster are 20 kgs -lOkgs +5 kgs and 13 kgs +10 kgs -5 kgs respectively.
The quantity of glue used in the mix has a significant effect on the setting time of the wet mix in the moulds. In the above example the use of 100 grams of glue instead of 50 grams causes a setting time of approximately 60 minutes. Using no glue at all causes a setting time of approximately 1 minute. Such a small setting time is impracticable in that not enough time is provided to pour the mix into the moulds before setting takes place. The preferred quantity of 50 grams of glue given in the above example provides a practicable drying time of 20 minutes. In addition to affecting drying time the glue also appears to improve the strength of the block and ensure a weather stable block after a few days of curing at room temperature.
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. EXAMPLE 2 An alternative building composition suitable for making blocks which are cheaper, lighter, but have relatively low structural strength 9 2 1 ~
properties is as follows:
a mix to make 10 blocks comprises:
sawdust 20 kgs cement 20 kgs casting plaster 12 kgs glue 100 grams together with a suitable quantity of water. Blocks produced from this mix, having dimensions identical to those of Example 1, weigh approximately half of the blocks of Example 1 i.e. 5 kgs. These blocks have the same fire rating characteristics but may not be used where structural strength is important.
In a preferred embodiment the building unit of the present invention is prepared as follows:

The moulds adapted to accept the wet mix of Examples 1 and 2 and suitable to product the blocks of Examples 1 and 2 as depicted in Fig. 1 are shown in Figs. 2 to 4.
Fig. 2 shows the general construction of the mould comprising a base member 6 to which are hingedly attached on opposite sides hinged sides 4.
On the two narrow proposed sides of the base 6 are affixed perforated side panels 5. The perforations are adapted to receive tubular members 7 threaded between opposing apertures and as depicted in Fig. 3.
Optionally, each mould may have a securing piece of overall dimensions similar to base 6 which, complete with securing members, can be used to secure the hinged sides 4 in a closed position to define an enclosed space of internal dimension suitable to produce the block of Fig.
1 having dimensions as outlined in Example 1.
Preferably, many such moulds are arranged in a closed position and side by side with their hinged sides in parallel juxtaposed relation. A
press arrangement of hydraulic or pneumatic or mechanical type can be used to hold the row or rows or moulds in closed position. Referring to Fig. 4, the action of these clamping devices would be in a direction generally shown by the arrows 9. As implied, more than one row may be arranged at the one time.
Once the moulds are setup in clamped, closed position, complete with tubular inserts 7 inserted, the wet mix as defined in Example 1 can be poured into the moulds via top apertures (not shown).
Using the preferred proportions outlined in Example 1 (including 50 grams of glue) a setting time of some 20 minutes is provided which allows WO 92/17416 21 ~ 8 0 4 2 PCI`/AU92/00114 sufficient time to pour the mix from the mixing arrangement (not shown) into the moulds.
Once setting is complete (after 20 minutes) the clamping means can be released, each individual mould 3 separated from the members of the group 8, the tubular inserts 7 removed, and finally, the set blocks removed therefrom.
Preferably, at least a few days are allowed for the blocks to obtain maximum dimensional stability before use in construction.
In use, the blocks of Examples 1 and 2 are light and durable as 10 previously described. The lightness is in part due to the composition and, in part due to the voids in the block. The building composition is such that sufficient mechanical integrity remains in the block structure despite these voids. In the examples the voids are substantially parallel tubular voids extending generally in one plane through the block. This particular 15 preferred construction allows electrical conduits and similar to be inserted through a plurality of blocks when such blocks are located one on top of the other. Therefore, when such blocks are used for the structure of walls requiring electrical or other services to be located therein it is a simple matter to thread such conduits through the multiple block 20 structure without any drilling or other guiding means being required.

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 follows:
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 approximately 1 30 square metre wall surface area of blocks (5 blocks) of dimension 600 mm x 300 mm x lOO mm. 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 35 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 block so produced has the following charact-eristics as construed in terms used in the trade:
the block will accept screws and nails without the need for any form WO 92/17416 210 8 0 ~ 2 PCI/AU92/00114 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 acoustic, 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 and5 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

2 I 0 8~0 4 2 PCT/AU92/00114 ~ -12-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.
The preferred cement is Portland cement. Sawdust may be any available sawdust, preferably in fine particle form. Hardwood sawdust provides particularly good compression characteristics. The lime is any commercially available lime, preferably that used for conventional cement work.

A mix having the composition of Example 4 is used to produce blocks as indicated in that Example.
A mortar mix is also prepared using the dry mix composition of Example 4. Sufficient water is added to the dry mix to create a mortar composition of satisfactory consistency when used to cement the above blocks together.
A wall is constructed using the mortar mix as above described and the blocks of Example 4.
Such a wall will exhibit a three hour fire rating and acoustic attenuation properties of some 40 decibells.

The following proportions, by weight, were mixed together with sufficient water to provide a workable mix:
Material Proportion Sawdust 70Z
Clay 10%
Cement 10%
Lime 10%
The sawdust used was that available from Australian Eucalypt trees, in this case a mix of Ironbark, Bluegum and Stringybark. This sawdust is of an oily consistency. The resulting mix was extruded into brick form using a clay brick extrusion machine. Bricks of a size llOmm by 200mm by 400mm and of a size llOmm by 200mm by 600mm were produced. The sawdust used appears to cause an exothermic reaction during extrusion which causes the bricks to cure in approximately three weeks without the necessity for firing.
Tests performed on these bricks when made up into walled panels of single brick thickness indicate a fire rating of four hours and an acoustic insulation of greater than 45dBA (typically in the range of 45-50dBA).
Compressive strength is of the order of 15MPa.

-13- 21~042 A composition comprising the following proportions by weight was mixed with sufficient water to provide a workable mix:
Material Proportion Sawdust 70%
Clay 15%
Cement 15%
As before this mix was extruded by a brick extrusion machine to form bricks of size llOmm by 200mm by 400mm and llOmm by 200mm by 600mm. These bricks, in a wall of single brick thickness, provided a slightly lower fire rating than for example 1 above but still sufficient to provide a four hour fire rating. The wall exhibited an acoustic installation capability of better than 45dBA. The compressive strength of the bricks is approximately 15MPa. Again, the sawdust used was derived from Australian Eucalypts, particularly a mix of Ironbark, Bluegum and Stringybark sawdust. Minor amounts of Greygum and Turpentine (which is a rainforest hardwood) were also available in the sawdust mix. Again, the bricks were cured within approximately three weeks.

A building composition mix comprising the following proportions by weight was mixed with sufficient water to provide a workable mix suitable for supply to an extrusion machine:
Material Composition Sawdust 60%
Clay 25%
Cement 15X
Again, the sawdust comprising sawdust derived from, principally, Ironbark, Bluegum and Stringybark. Minor amounts of Greygum and Turpentine sawdust were also present. Curing time was the order of three weeks. Fire rating for a single thickness brick wall made from bricks of dimension either llOmm by 200mm by 400mm and llOmm by 200mm by 600mm was four hours. The acoustic insulation of the wall was 45dBA. Compressive strength of the individual bricks was 15MPa.
It is a requirement of the method of manufacture of the bricks that the bricks be allowed to dry naturally if the fire insulation rating is to be achieved. This is aided by the exothermic reaction which appears to be caused by the use of the eucalypt based sawdust.

A building unit, in particular a building block having desirable WO 92/17416 2 ~ O ~ 0 4 2 PCI/AU92/00114 properties and of dimensions 600mm x 200mm x lOOmm is constructed as follows:
A dry mix comprising by weight 50% sawdust 35% cement 15% lime of sufficient quantity to fill five moulds of internal dimension 600mm x 200mm x lOOmm 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 lOOmm. 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 lOOmm 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 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.

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 follows:
a dry mix comprising sawdust 60%;
cement 30%;
lime 10%
of sufficient quantity to fill five mounds of internal dimension 600 mm x 300 mm x 100 mm is mixed with 25 litres of water to produce approximately 1 square metre wall surface area of blocks (5 blocks) of dimension 600 mm x WO 92/17416 21~ 8 0 ~ 2 PCI`/AU92/00114 300 mm x 100 mm. The wet mix is poured into moulds of construction similar to those 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 similar to that 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 10 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 acoustic, 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 90Z of 35 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 b7Ock with the characteristics described. Ambient conditions and the quality of the W O 92/t7416 2 ~ ~ 8 ~ P ~ /AU92/00114 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.
Example 11 1) Fresh sawdust, 520 kg 2) Cement, 480 kg

3) Lime, 100 kg

4) Copper sulfide, 500 grams

5) Calcium chloride, 3%

6) Water, 300-350 litres This produces a mixture of 1 cubic metre in volume. After adding all the components, it is mixed for 3-5 minutes in a mixer. It is then poured into vertical moulds between villaboard. The mould is opened after 24 hours. The panels are then dried in a flat position. The panels are laid on top of each other, but separated by wooden slats to allow breathing and evaporation of the panels. The panels can be installed approximately after 4-S weeks. The panel can be installed either in vertical or horizontal position.
Using the casting method, the formula for producing panels and blocks without villaboard is exactly the same.
Example 12 1) Fresh sawdust, 620 kg 2) Cement, 480 kg 3) Lime, 100 kg 4) Copper sulfide, 7-10 kg 5) Calcium chloride, 5-7%
6) Water, 200-250 litres WO 92/17416 2 ~ ~ 8 0 4 ~ PCI/AU92/00114 This formula is slightly different to the previous Example and provides greater plasticity. A similar formula was used on a small experimental extrusion machine. The result was quite good.
On a large extrusion machine it may be necessary to alter the content of calcium chloride, while leaving the other components the same. The quality of the extruded product has the same fire-resistance and sound insulation properties as cast material, and will have a lower shrinkage level than cast material. Cellular panels (i.e. with holes) produce a lighter material and enable quicker drying of the product.
10 ExamDle 13 1) Fresh sawdust, 40%
2) Woodchips, 22% - 12%
3) Cement, 48%
4) Lime, 10%
lS 5) Copper sulfide, 8-10 kg 6) Calcium chloride, 5-7Z

7) Water 300-350 litres The composition should be mixed for approximately 3-5 minutes after being put in the mixer.
It is recommended that the tiles and blocks should be cut no earlier than 3 days after pouring.
In respect of woodchips fresh softwood is recommended.
It is also possible to produce a tile or block in a press which is used for blocks and tiles. It is only needed to change the percentage of water, reducing it to 299 litres. Of course, the woodchips and sawdust must be fresh. The large percentage of calcium chloride and copper sulfide forms a binding reaction in the blend.
ExamDle 14 The method for producing aerated concrete is different. It is desirable to use a mixer with a planetary action at a high rpm. The direction of mixing is at least 15-20 minutes. The formula must be the same, except that it has a high percentage of calcium.
1) Fresh sawdust, 520 kg 2) Cement, 480 kg 3) Lime, 100 kg 4) Copper sulfide, 500 grams 5) Calcium chloride, 5-7%
6) Water, 300-350 litres Experiments have shown that after 15 minutes the mass forms micro air WO 92/17416 21 0 8 0 ~ 2 18 PCr/AU92/00114 bubbles and increases in volume. It can then be poured in moulds of any shape.
Because of the air content, the product has been shown to be lighter by about 20% than casted material.
Exam~le 15 A typical specification requiring a wall 75 to 100mm in thickness weighing not more than 1,000 kgs x m3, having a four hour minimum fire rating and a sound rating of 46 dC would require the following formula:
fresh sawdust 640 kgs cement 280 kgs calcium chloride 20 1 i tres copper sulphate 400 grams animal glue 3 kg powdered milk 500 grams lS Other building units such as wall and floor tiles, blocks of different dimensions, (with or without internal voids) and laminate structures (particularly for walls) are contemplated but are not to be taken as limiting in the applications to which the advantageous characteristics of the building composition described may be put. Laminate structures in particular may comprise a core comprising the building composition mix material with outer layers on one or both sides being wood panelling, other forms of synthetic panelling, plaster mixes, rendering mixes, insulation material, paint compositions and other materials commonly used in the building trade to achieve desirable effects. For example, where building units comprising the building composition of the invention are used for interior walls it may be desirable to fix various forms of wood or synthetic panelling to the building units. When used for exterior walls various forms of external cladding may be desirable. Additionally, insulation materials may be affixed to one or more surfaces to enhance the insulation and acoustical properties of the building unit.
Some alternative materials can be used to replace the materials specified in the examples of the preferred embodiment. For example, milk powder can replace the pearl glue or animal glue. There is some loss in structural integrity in so doing. Wheat husks or wood chips can be used to replace the sawdust. These relatively coarse particles will, however, prevent internal voids in the building units from being allowed to run close to the edges of the block. Structural integrity and ability to retain items such as screws and nails may also be adversely affected.
The mortar composition of one aspect of the present invention can W 0 92/17416 210`~8 0 4~2 ~ PC~r/A U92/00114 also be applied to presently available building materials, including Gybrock or equivalent. This will improve the acoustic properties and fire rating properties of the original materials.
A test wall having a 3 hour fire rating was constructed as follows:
Method of Construction of Test Wall A. "Cement Mix" comprises 50% casting plaster and 50% Type A
Portland Cement ~prior to water addition).
B. Blocks are to be laid in stretcher bond.
1. Lay 5mm thick bed of cement mix on floor.
2. Batter entire end of block with a 5mm bed of cement mix and butt up to starting point.
3. Repeat this process for first course.
4. When laying second course overfill rebate of first block with cement mix but maintain the 5mm thick bed to outside edges, strike off excess cement mix.
5. Repeat step 2 tapping block down to maintain a finished bed thickness of approximately 3mm thick.
6. When butting blocks to existing walls use standard bricklaying methods, at corners ditto.
The method of constructing the block is as follows:
A block mix is made by mixing a dry mix according to the proportions previously outlined, then mixing with water in a mixing machine and pouring the resultant wet mix into moulds. Alternatively, a wet casting plaster and Portland Cement Mix may be made independently of a sawdust mix and the two then combined together at the mixing stage.
In a preferred embodiment the moulds are arranged in series as batches. The cylindrical perforations are effected by passing a series of cylindrical rods through supporting holes in the mould walls. In this way a number of blocks may be made quickly and cheaply at the one time. Once dry the cylindrical poles are removed and the dried blocks are tipped from the mould assembly. Completed blocks are shown in Fig. 1 and made according to the method outlined weigh approximately 2 kgs. each. The block ls preferably for use as a non-loadbearing unit. However, relatively light loads can be supported.
Advantages of the present invention include the following:-1) Various formulas can be used to produce brick/blocks of any size and shape when poured into moulds.
2) Moulds can be filled by hand and or by machine.
3) Various formulas can be used to produce bricklblocks and panels WO 92/17416 21 0 g O ~ 2 PCI`/AU92/00114 of any size and shape poured vertically or horizontally both by hand or by machine.
4) Various formulas can be used to make objects of any shapes by pouring into moulds.
5) Various shaped objects could be made by carving, shaping blocks of solidified material by using wood working tool in the same manner as wood blocks.
6) The mixtures could also be used to provide protection against heat, fire, noise in existing structures by pouring the material in-situ over existing timber floor.
7) The mixtures could also be sprayed on new and existing structures as to provide a shield against heat and fire.

8) By reducing the amount of water in the mixing panels and block can be manufactured by the use of extrusion machines.
lS This method is a faster way of production capable of reducing labourcontent. The extrusion machines would be computerised which would guarantee a much better quality control. The reduction in water content would also reduce the time required for curing.

9) The addition of reinforcement material such as ropes, nets and nylon fibres would considerably increase the strength of the panels against wind loading and structural requirements. Because of this these panels could be used as barriers against fire on boundaries and tenancy separation walls.

10) Able to produce a light weight product with high sound and fire resistance suitable for a multitude of applications in the building industry.

11) The product could be shaped into bricks/blocks/panels and poured in-situ or sprayed.

12) The manufacturing could vary in production from being super labout intensive to a fully computerised extrusion process requiring very little labout and operating around the clock.

13) The ingredients are freely available around the world, sawdust at present being problematic in its disposal, is the main ingredient.

14) The panels manufactured with this product could be further fortified by the usage of ropes, nets or fibres to suit wind loading and any other structural requirements.

15) Panels, bricks, blocks manufactured with this product can be used both internally or externally.

16. Formulas vary according to the specific properties requirements.

WO 92/17416 ~ i 21 ~ 8 0 4 2 PCI/AU92/00114 The foregoing describes only a few embodiments of the present invention, and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope and spirit of the present invention.

Claims

CLAIMS:

1. A building block composition suitable for making a building unit, said composition comprising by dry weight:
fresh sawdust - in the range 20-70%
cement in the range 20-50%
lime in the range 5-20%

2. The composition according to claim 1 wherein the composition comprises, by dry weight, about 50% sawdust, about 35% cement, and about 15% lime.

3. The composition according to claim 1 wherein the composition comprises, by dry weight, about 60% sawdust, about 30% cement, and about 10% lime.

4. The composition according to claim 1 wherein the composition comprises, by dry weight, about 70% sawdust, about 20% cement and about 10%
lime.

5. The composition according to claim 1 wherein the composition comprises, by dry weight, about 50% sawdust, about 40% cement, and about 10% lime.

6. The composition of any one of claims 1 to 5 further comprising approximately 1% by weight of glue.

7. A building block composition comprising, by weight, between 60 and 70% fresh sawdust, between 15 and 25% clay and approximately 15% cement.

8. A building block composition comprising about 70% fresh sawdust, about 10% clay, about 10% cement and about 10% lime.

9. A building block composition according to either claim 7 or claim 8, wherein Eucalypt derived sawdust is used.

10. A building block composition according to claim 9, wherein the Eucalypt from which the sawdust is derived are one or more of Ironbark, Bluegum and Stringybark.

11. A building unit manufactured from a building composition according to any preceding claim.

12. A building unit according to claim 11 manufactured in solid block form of approximate dimension 600mm x 300mm x 100mm.

13. A building unit according to claim 11 manufactured in solid block form of approximate dimension 600mm x 200mm x 100mm.

14. A method of making a building unit comprising the steps of initially creating a building composition according to any one of claims 1 to 10, producing a wet mix by mixing said composition 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.

15. The method according to claim 14 wherein said wet mix is scaled proportionately on the basis of approximately 25 litres of water together with said composition in sufficient quantity to manufacture 5 units of dimension 600mm x 300mm x 100mm.

16. The method according to claim 14 wherein said wet mix is scaled proportionately on the basis of approximately 25 litres of water together with said composition in sufficient quantity to manufacture 5 units of dimension 600mm x 200mm x 100mm.

17. A mortar mix comprising a sufficient quantity of water mixed together with the composition according to any one of claims 1 to 10.

18. A building block composition comprising, by dry weight:
fresh sawdust 20-70%
cement 20-50%
plaster 5-20%

19. A building block made from the composition according to claim 18, said composition in an unset state further comprising 50 grams of glue and 10 litres of water per cubic metre of composition.

20. A building block comprising a mix whose dry weight composition is approximately 35% casting plaster, 45% type A Portland cement and 20%
fresh sawdust, said composition mixed with water and moulded and dried to form said lightweight building block, said block incorporating a plurality of substantially parallel perforations extending therethrough.

21. A building block according to claim 20, wherein said plurality of substantially parallel perforations take the form of cylindrical channels.

22. A method of making a building unit, comprising the steps of initially creating a dry composition comprising by dry weight about 20-70%
fresh sawdust, 20-50% cement and 5-20% plaster; producing a wet mix by mixing said dry composition with approximately 50 grams of glue and 10 litres of water per cubic metre of wet mix; pouring said wet mix immediately into at least one mould; allowing said wet mix to set in at least one mould; and removing said building unit from said at least one mould upon setting of said wet mix; said setting taking place over a relatively short period of time; said building unit produced by said method not requiring any further curing or aging before use.

23. A building unit made according to the method of claim 22.

24. A building block composition according to any one of claims 1 to 10, further comprising one or more of calcium chloride, copper sulfate, animal glue and powdered milk.