WO1987004699A1

WO1987004699A1 - Composite plaster block

Info

Publication number: WO1987004699A1
Application number: PCT/AU1987/000026
Authority: WO
Inventors: Leon Kruss
Original assignee: Leon Kruss
Priority date: 1986-01-31
Filing date: 1987-02-02
Publication date: 1987-08-13
Also published as: WO1987004700A1; EP0295245A1; EP0295245A4

Abstract

A dry mix suitable for making a building unit comprising, by dry weight, 10 to 50% sawdust, 20 to 50% cement and 5 to 40% plaster (calcium sulfate). In a preferred form the mix may also contain a glue. The resulting building unit may be formed into building blocks of preferred size 600mm x 300mm x 100mm. These building blocks when manufactured into their final form have improved thermal insulation and load bearing properties.

Description

Composite Pl aster Block

TECHNICAL FIELD

The present invention relates to a building 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, rosin 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 rosin 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 into the composition.

G.B. 1552226 to S. Morris (Yeovil) Limited details a composition which includes as an essential ingredient 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% klinker breeze (having a cellular structure) 0-60% pulverised bark 20-70%

In order to achieve lightness this structure relies upon a "cellular" structure generated by use of the clinker breeze and the pulverised bark.

A further citation is Australian Specification AUA 39887/85 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 the citation, numerous ingredients are used to achieve the desired effects. In particular, a substantial proportion of lime has been used.

The objects of the above citations 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.

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 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. It is an object of the present invention to provide an improved building composition, building unit and method of making same in terms of at least some of the above criteria with reference to previously known materials and methods.

DISCLOSURE OF THE INVENTION According to the present invention there is provided a mix suitable for making a building unit, said mix comprising, by dry weight, about 30% sawdust, 50% cement and 20% plaster.

In a further form, there is provided a mix suitable for making a building unit, said mix comprising, by dry weight, about 40% sawdust, 40% cement and 20% plaster. In a further broad form there is provided a mix suitable for making a building unit, said mix comprising by dry weight: sawdust 30% (range 10 to 50%) cement 50% (range 20 to 50%) plaster 20% (range 5 to 40%) Preferably, a building unit is made from the above mix, said mix in unset state further comprising approximately 500 grams of glue and 200 litres of water per three cubic metres of mix.

Preferably, there is provided a building block made from the above mix, said mix, in an unset state, further comprising 500 grams of glue and 200 litres of water per three cubic metres of mix.

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 comprising by dry weight about 30% sawdust, 50% cement and 20% plaster; producing a wet mix by mixing said dry mix with approximately 500 grams of glue and 200 litres of water per three cubic metres 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.

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 molds of Example 2;

Figure 2 depicts a mold in an open state suitable for making a block of the preferred embodiment;

Figure 3 depicts the mold of Figure 2 with tubular inserts inserted; Figure 4 depicts a group of molds as arranged for mass production.

MODES OF CARRYING OUT 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 mix suitable to produce a block having at least some of the properties comprises the following components (by dry weight): sawdust 23% +12%, -12% cement 47% +12%, -23% plaster 30% +23%. -12%

EXAMPLE 1

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 100mm. The wet mix is poured into molds 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 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.

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 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 -10kgs +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 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: EXAMPLE 3

The molds 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 mold 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 mold 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 molds 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 molds 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 molds are set up in clamped, closed position, complete with tubular inserts 7 inserted, the wet mix as defined in Example 1 can be poured into the molds 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 sufficient time to pour the mix from the mixing arrangement (not shown) into the molds.

Once setting is complete (after 20 minutes) the clamping means can be released, each individual mold 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 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 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 structure without any drilling or other guiding means being required. The foregoing describes only one embodiment and one method of making the embodiment 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. Firstly, 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.

Annexed hereto and forming part of the specification are the results of fire resistance tests, sound transmission loss tests and compressive strength tests carried out on blocks constructed according to Examples 1 and 2.

Claims

1. A mix suitable for making a building unit, said mix comprising by dry weight: sawdust in the range 10% to 50% cement in the range 20% to 50% plaster in the range 5% to 40%

2. A mix suitable for making a building unit, said mix comprising, by dry weight, about 30% sawdust, 50% cement and 20% plaster.

3. A mix suitable for making a building unit, said mix comprising, by dry weight, about 40% sawdust, 40% cement and 20% plaster.

4. The mix of claim 1 or claim 2, said mix in unset state further comprising approximately 500 grams of glue and 200 litres of water per three cubic metres of mix.

5. A building block made from the mix of any one of claims 1, 2, 3 or 4.

6. A method of making a building unit, comprising the steps of initially creating a dry mix comprising by dry weight about 30% or 40% sawdust, 50% or 40% cement and 20% plaster; producing a wet mix by mixing said dry mix with approximately 500 grams of glue and 200 litres of water per three cubic metres 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.

7. A building block made according to the method of claim 6.

8. The building block of claims 5 or 6 of dimension about 600mm x 300mm x 100mm.

9. The building block of claim 7 or 8 having a plurality of cylindrical holes extending therethrough.

10. The building block of claim 9 having holes as depicted in Fig. 1.