GB2156333A - Brick - Google Patents

Abstract

A plaster brick comprising major portions of plaster, particulate wood and preferably lime, a colloid such as milk powder, a surfactant such as detergent, and a small amount of glue such as animal glue.

Description

SPECIFICATION Brick The present invention relates to a plaster brick, to a method of producing the brick, and to a mould for shaping the brick.

In the past, bricks made from plaster have not been a particularly popular building material. This is partly the result of plaster bricks being heavy and lacking in strength. Also, plaster bricks have generally been manufactured by methods which leave rough surfaces on the bricks, giving the bricks and undesirable finish and appearance, and usually requiring a further plastering of the wall constructed from this type of brick.

According to the present invention, a brick comprises a mixture of plaster and particulate wood.

Preferably, the plaster is chosen from casting plaster, pottery plaster, hardwall plaster and stopping plaster. Casting plaster is the most preferred plaster for the brick of invention.

The particulate wood comprises chips of wood, wood shavings or sawdust, preferably ranging in size from 2 mm to about 10 mm. Different colours of wood can be chosen in order to alter the colour and appearance of the finished plaster bricks.

The plaster brick preferably also includes lime, which is added in order to quicken the setting time of the brick.

The brick may also contain a minor portion of a colloid such as milk, preferably added in a dry form as milk powder.

The brick may additionally contain a minor portion of a surfactant which may also have dissolved in it a glue, preferably animal glue. The surfactant and glue may assist in wetting and binding the ingredients of the brick together to strengthen the brick.

The ratio of plaster to wood chips is preferably between 20:80 and 80:20 by weight. Most preferably, approximately equal amounts, or a small excess of plaster over wood chips, are used. A preferred embodiment of the invention comprises a plaster brick have 35 to 65% plaster, 15 to 40% wood chips or shavings, 10 to 25% lime, 0.5 to 3%milk powder as the colloid, 0.5 to 3% detergent or other surfactant, and up to 0.05% animal glue. If the other preferred ingredients are included, then the most preferred quantities are approximately 50% plaster, 35% wood chips, 15% lime, about 1% milk powder and about 1% detergent having a small quantity of animal glue dissolved in it. All these proportions are by weight. These proportions can be varied by a relatively small amount, without greatly affecting the brick produced.In producing the brick, the relative proportions of the material used will often be measured approximately, and so these preferred amounts are intended as a guide only.

Sufficient water will be added to set the brick, which will harden within 10 minutes once the water has been added. The shape of the brick is determined by that of the mould in which it is produced.

The ingredients of the plaster brick are mixed together with water, and allowed to harden in a mould to give the brick its desired shape. Preferably, the mould has very smooth inner surfaces on the side or sides corresponding with ornamental side or sides of the brick. The smooth inner surface of the mould produces a very smooth surface on the plaster brick. By choosing an appropriate size and variety of wood chip, and choosing an appropriate ratio of plaster to wood chips, a plaster brick can be produced with resembles marble or cork in appearance. The brick produced using a smoothsided mould has an extremely smooth surface, which is an important improvement over bricks produced using prior art methods. The brick sets quickly once water is added and this reaction is exothermic.Therefore, the inner surfaces of the mould are preferably covered with a smooth heatresitant plastic material.

The plaster brick of the invention is fire-resistant, is much lighter than solid plaster bricks, and is much stronger than previously constructed bricks.

The brick may be used to produce interior decorative walls in buildings, internal partitioning, or the wall around lift wells, for example. The bricks of the invention are strong and much lighter in weight than conventional concrete or clay bricks, and so are useful in buildings where weight loading is to be kept to a minimum.

According to the invention, a method for producing a brick comprising plaster and wood chips comprises (a) mixing plaster and particulate wood together, (b) adding a suitable amount of water to the mixture resulting from part (a), (c) immediately placing the mixture resulting from step (b) in a mould having at least one smooth inner face, (d) allowing the mixture from step (c) to harden, and (e) opening the mould and removing a plaster brick.

When other ingredients are included, the lime, milk powder and detergent which has had animal glue previously dissolved in it, they are all mixed and/or dissolved in the appropriate amount of water. This aqueous mixture is added to the plaster and wood chips as in step (b) above.

Once water is added, the plaster mixture begins to set, and this reaction is exothermic. Therefore, as soon as the water is added the plaster mixture must quickly be placed into a mould, to produce a brick.

The invention also concerns a mould for shaping a brick, said mould being of a generally hollow prismatic shape having at least two hinged detachable sides to enable the mould to be substantially unfolded to allow removal of the shaped brick.

Preferably at least one of the inner faces of the mould is particularly smooth, and most preferably both of the major inner faces are smooth.

It is preferred to use this type of mould to prepare the plaster bricks of the present invention.

The mould is of a generally rectangular prismatic configuration. Most preferably, the mould pro duces plaster bricks according to the invention of a size equivalent to 20 normal house bricks. A preferred brick has dimensions of 100 x 300 x 600 mm.

The mould comprises a number of hinged panels which can be folded together and clipped to comprise a hollow rectangular prismatic shape. The panels are clipped together and held in place by any suitable catch means. The panel comprising one of the smallest ends is opened, and the fluid plaster/wood chip mixture is forced into the mould to fill it. The end is closed and the plaster brick is allowed to solidify. The hardening process takes approximately 2 or 3 minutes when lime forms part of the mixture. When the brick has substantially hardened, the mould is unclipped so as substantially completely to unfold. The catches holding the panels of the mould in place are released, and the mould is unfolded so as to lie flat.

The hardened plaster brick can then be lifted out of the mould.

In order to produce a smooth surface on the plaster brick, one and preferably two of the inner surfaces of the mould are particularly smooth.

Most preferably these are those adjacent to the two largest sides of the brick, which are intended to be the facing portion of the brick. The smooth surface can be produced by any means, such as by covering the inner surface of the appropriate panels of the mould with sheets of stainless steel, smooth, hard plastics, or any similar smooth material. However, both the material from which the mould is constructed and the material making up the smooth covering on an inner surface of the mould should be heat-resistant, so as not to be damaged by the heat created as the plaster brick sets.

The edges of the brick may also be bevelled so that a wall of bricks can be erected and held in place by the interlocking mechanism of adjacent convex and concave bevelling. Alternatively'and preferably, a central ridge or groove can be shaped in two opposite edges, or in all four edges of the brick, in such a manner that adjacent bricks will interlock. Normally, opposing edges of the brick will have opposite orientation; for example, one edge will have a groove while the opposite edge will have a corresponding ridge so that adjacent bricks interlock.

The following Example illustrates the invention.

Example 1 Water (100 litres), lime (40 kg), milk powder (2 kg) and detergent (2 litres) having about 35 g of animal glue dissolved in it were mixed together.

Separately, dry casting plaster (120 kg) and wood shavings (about 80 kg) were mixed together.

The shavings and plaster were quickly mixed together with the water containing the other ingredients. The resulting plaster mixture was stirred rapidly for a few seconds, and the mixture tipped into 15 moulds.

The moulds were of a size to produce bricks 600 x 300 x 100 mm. The two major inner faces of the moulds had a smooth heat-resistant plastic covering. The mould could be unfolded to allow the bricks to be removed, and its sides are held together by clips. One side was left open for filling, and once the mould was full of plaster, this remaining face was closed and clipped in place. Normally a small amount of plaster will be forced out as the last face is closed, ensuring that no air space is left in the mould.

The two inner faces of the mould opposite the larger edges of the brick each have either a centrally-located groove or a ridge running longitudinally along the face, the ridge and groove having corresponding dimensions. The plastic bricks produced from these moulds will interlock with the row of bricks underneath. When building a wall, mortar may not be necessary as a result of this interlocking, but for the sake of stability and for noise and temperature insulation it is desirable to use at least some mortar between the plaster bricks. If necessary, grooves and ridges may be incorporated in the smaller two edge faces of the bricks (i.e. the sides of the brick), to allow further interlocking between bricks placed side by side.

The plaster sets in about 3 to 4 minutes, and the bricks were removed from the moulds after 10 minutes. The plaster bricks were aged for about 10 days, during which period they lose moisture, and become stronger. Each such brick weighs about 18 or 19 kg at the end of this period.

Plaster bricks were tested for their fire-resistance, strength and insulating abilites.

(a) To test fire-resistance, the plaster bricks were made into a wall in an oven at the Experimental Building Station of the Government Department of Housing and Construction, in Victoria, Australia.

The fire testing showed no failure at all in the wall after 241 minutes. The bricks have been given an official fire rating of 4 hours, which means that they are essentially non- combustible under normal conditions.

(b)The comparative strength of the plaster bricks of the invention was tested. It was found that their strength tends to increase with age. The plaster bricks were found to have a comparatble strength to other similar building material, and to be well suited for, for example, interior walls or partitions of buildings, stairs and lift wells.

(c) The acoustic insulation abilities of the bricks was tested by N.A.T.A. and given a STC rating of 41 dB which is excellent. If rendering was used between bricks in a wall, the STC rating rose to 45 dB.

Claims (8)

1. A brick comprising a mixture of plaster and particulate wood.

2. A brick according to claim 1, which further comprises minor portions of one or more of lime, colloid, surfactant and glue.

3. A brick which comprises 35 to 65% plaster, 15 to 40% particulate wood, 10 to 25% lime, 0.5 to 3% colloid, 0.5 to 3% surfactant and up to 0.05% glue.

4. A brick according to claim 2 or claim 3, wherein the plaster is casting plaster, the colloid is milk powder, the surfactant is a detergent, and the glue is animal glue.

5. A method for producing a brick comprising the steps of: (a) mixing plaster and particulate wood together; (b) adding a suitable amount of water to the mixture resulting from part (a); (c) immediately placing the mixture resulting from step (b) in a mould having at least one smooth inner face; (d) allowing the mixture from step (c) to harden; and (e) opening the mould and removing a plaster brick.

6. A method according to claim 5, wherein the water in step (b) includes one or more of lime, colloid, surfactant and glue.

7. A method according to claim 5, substantially as described in the Example.

8. A mould for shaping a brick, the mould being of a generally hollow prismatic shape having at least two hinged detachable sides to enable the mould to be substantially unfolded to allow removal of a shaped brick.