Method of Forming a Prefabricated Block

BACKGROUND

a. Field of the Invention

The present invention is directed towards a method of forming a prefabricated block, particularly a prefabricated block having a predetermined pattern of inclusions in one surface. The method is particularly directed towards a method of forming a concrete block which includes a brickwork pattern of bricks in a front face so that, when installed, that face looks substantially the same as a brick wall.

b. Related Art

Pre-cast blocks, usually of concrete, are used in many different situations. They are often used to create temporary or permanent walls, such as retaining walls, on industrial sites, but suffer the disadvantage that the concrete walls created are not aesthetically pleasing. In many cases, after the concrete wall has been installed, the blocks are painted or otherwise disguised to improve the look of the wall. In some cases a false brick wall is constructed in front of the concrete wall to hide it. Such additional, non-functional decorative work increases the time and costs of installation.

It would therefore be desirable to have pre-cast blocks for making such walls that include a brickwork pattern on one face so that the finished wall gives the impression of a brick wall, which is generally accepted as looking better than a concrete wall.

Prefabricated blocks including a brickwork pattern on one face can be created by hand laying a brick wall section of the desired block area. Such a block requires time and skill to create due to the hand pointing between the bricks that is required. Such a brick section may also not be as strong as, for example, a

concrete wall section of an equivalent size and may therefore need reinforcement at additional cost.

A face of a concrete wall section can be moulded to give the 3-D impression of brickwork, by the texture and colour of the 'bricks' do not provide a convincing impression of real brick unless further processing operations, such as colouring, are performed.

Another method that has been used to make a concrete block more aesthetically pleasing is the use of thin sections of brick material to effectively 'tile' a brickwork pattern onto a surface of concrete block. This tiling operation can be performed manually, or by using computer controlled apparatus, both of which operations are time consuming and costly. However, such tiling can suffer in frost or other adverse weather as the tiles can become detached and fall from the block, spoiling the effect.

The use of a mould has been tried, with the mould being loaded with bricks and then filled with concrete. There are several problems with such methods in that the concrete tends to seep to the front face of the brick and stain them. It has also been found that, with known moulding methods, a lip is created between the front face of the brick and the concrete which leads to the product requiring pointing before it has the appearance of a real brick wall and to avoid damage to the product through exposure to frost and the like.

It is an object of the present invention to provide a more convenient method of forming a prefabricated block.

SUMMARY OF THE INVENTION

The invention provides a method of forming a prefabricated block, the method comprising the steps of: a. providing a mould having side walls and a first mould face, the first

mould face including a resiliently deformable surface layer and further including a predetermined pattern of protrusions, the predetermined pattern of protrusions defining a plurality of load sites; b. providing a plurality of inclusion members, each inclusion member having a display face defined by a periphery and loading the inclusion members into the load sites of the mould such that display face of the inclusion members is adjacent the first mould face of the mould and the protrusions substantially surround the periphery of the display face; c. using at least one insert to contact the inclusion members and force the display face of the inclusion members into the resiliently deformable surface layer so that the surface layer is deformed; d. pouring a matrix into the mould; e. providing a second mould face and using the second mould face-to substantially seal the mould; f. partially curing the matrix such that the inclusion members are bound into the cured matrix and are retained in the predetermined pattern, but the matrix has not fully hardened; g. inverting the mould; h. removing the first mould face from the mould to expose the display faces of the inclusion members cleaning the display faces of the inclusion members; i. fully curing the matrix; and j. removing the cured prefabricated block from the mould.

The inclusion members can be any suitable size or shape and can vary in size or shape as desired depending upon the pattern to be created. It is preferred that the inclusion members all have a substantially identical outer shape as this allows any inclusion member to be placed in any load site, which facilitates loading of the mould.

The inclusion members are preferably substantially rectangular or square in shape as this allows close packing of the inclusion members within the mould. Close

packing of the inclusion member can result in a reduced level of the matrix being visible between the display faces in the prefabricated block.

Substantially all of the inclusion members may be made from brick. It is preferred that the inclusion members are bricks, and more particularly that the inclusion members are half bricks. Half bricks are, in this case, bricks that have been cut along a central long axis of symmetry to form two substantially identical half bricks each having a display face. The display face being the brick face that would commonly be visible in a brick wall. It should be understood that the half bricks need not be cut from whole bricks, but could be manufactured to be substantially the same size and shape. It should also be understood that inclusion members of different colours or materials could be used to create an additional pattern in the pattern of inclusion members. Inclusion members having a display face substantially the same size as a brick could be specially fabricated from brick to reduce the brick content of the final block. The inclusion members are preferably at least 2cm in depth from the display face to a face opposing the display face.

It is preferred that the predetermined pattern of the protrusions is such that the load sites are arranged in a brickwork pattern and that the load sites are shaped to accept a display face of a half brick. A mould including such a pattern would, if loaded with half bricks, result in a finished block having half bricks in a brick wall arrangement secured in a matrix.

It is preferred that the matrix poured into the mould over the inclusion members is concrete, but it may be any other suitable matrix, for example resin, depending upon the desired aesthetic and structural properties of the final product.

Reinforcing structures such as a metal mesh may be placed into the mould before or during pouring of the matrix to reinforce the cured matrix, for example reinforced concrete.

The protrusions are located on at least the first mould face, but may also be located in side walls of the mould. The protrusions preferably protrude from the

first mould face such that they protrude between inclusion members loaded into the load sites such that the matrix extending within a gap between inclusion members is set back or recessed from the display faces. An upper surface of the protrusion that may be in contact with, or shape, the poured matrix is preferably curved so that the matrix extends closer to the display face adjacent the periphery than in the centre of the gap between the inclusion members. Such a shaping of the matrix in the gaps between the inclusion members gives the matrix a similar shape to pointing used in brickwork and provides similar weather protection to the inclusion members. It should be understood that the shape of the protrusion may be varied to provide other effects if desired. The protrusions and first mould surface may be protected by a plastic or other sheet if desired to protect the mould face and facilitate removal of the cored product.

The use of at least one insert to force of the inclusion members into the deformabie surface can be achieved by any suitable means, for example a metal mesh could be placed over the inclusion members and a force applied so that the inclusion members are forced into the deformabie surface and the metal mesh secured in place. However, it is preferred that, after loading of the load sites with inclusion members, resiliently deformabie elongate members are placed within the mould and then wires are passed over the elongate members and tightened so that the elongate members are compressed and apply a force to the inclusion members causing them to be forced into the deformabie surface.

It should be understood that the inserts could be forced into the deformabie layer by contact between the at least one insert and the second mould face as it is being moved into place. This would require the matrix to be added between the walls and the second mould face before the mould is closed, or the matrix could be poured through openings in the second mould face which are later sealed.

The mould comprises three sections, a first mould face, the side walls, which may be separate wall joined together, and a second mould face. The first and second mould faces can be secured to the side walls to substantially enclose a mould

volume. The side walls may also include a pre-stressing frame allowing pre- stressing wires to be arranged and stressed within the curing matrix so that a pre- stressed block can be formed, particularly a pre-stressed concrete block.

When the prefabricated block to be formed is a pre-stressed block, it is preferred that 'V profiled metal strips are laid across the inclusion members and are arranged substantially perpendicular to the direction in which the pre-stressing wires will extend. It should be understood that the direction need not be substantially perpendicular, but that this is most efficient for rectangular or square geometries. The 'V profiled metal strips are arranged so that one leg of the 'V sits on the inclusion members with the other leg extending away from the inclusion members. As the pre-stressing wires are initially tightened the upstanding leg is forced towards the other leg thereby applying a force to the inclusion members forcing them into the compressible surface. Other components may be used to interact with the pre-stressing wires and inclusion members, but such V profiled strips have been found to be particularly suitable as they are cheap and readily available. The number and distribution of the pre-stressing wires for a pre- stressed block can be determined by known methods and this will not be discussed in detail here. It should be noted that all the wires need not be in contact with the 'V strips, in particular, there may be two rows of pre-stressing wires, and only one of the rows may be in contact with the ¹ V strips.

The same 'V profiled strips may also be used in a normal block, or in a reinforced block. To form a normal pre-cast block, the 'V strips could be placed over the inclusion members and then wires tensioned above them to force the inclusion members into the deformable layer. However, there would be fewer wires than would be required for pre-stressing the block as this saves on the cost of wires and also on the weight of the block. In such a non-pre-stressed block, as few as two or three tensioned wires may be used to compress the 'V strips. To provide additional reinforcement, a grid, preferably of metal, could be placed between the 'V strips and the wires as this could help to stabilise the block and would also distribute the compression force of the wires more evenly. Such a grid could also

be used in a pre-stressed block.

In order for such wires to compress or apply a force to any such insert, whether the insert is deformable or not, each wire which will apply a force when tensioned must run between two points of the mould such that a straight line joining those points would pass through the position in which the insert would sit when uncompressed and the deformable layer substantially un-deformed. In this way the slack wires can be positioned and then tensioned such that they apply the force to the inserts. The amount of force applied can be adjusted by varying the tension of the wires, the deformability of the insert and the position of the points in the mould through which the wire must pass.

It should be noted that he inclusion member may also be the insert and any wires could therefore effectively directly contact the inclusion members.

The elastically deformable surface on the first mould face may be any suitable material, but is preferably a synthetic rubber layer having a depth of between 1mm and 5mm, preferably between 2mm to 4mm.

The mould face may be covered in a protective sheet, preferably a plastic sheet before loading of the inclusion members so that the mould face requires less cleaning between moulding cycles. The plastic sheet also helps to release the inclusion members from the mould face.

The mould is preferably made from steel so that it can support the weight of the matrix and inclusion members during the pouring, curing and inverting process. The mould is preferably arranged so that the first mould face is substantially horizontal when the matrix is being poured.

The side walls of the mould extend away from the first mould face to define the edges of the mould and to retain the matrix as it is poured into the mould. The walls extend above the height of the inclusion members such that matrix can be

poured into the mould to cover the inclusion members as this allows the matrix to form a continuous layer which can provide structural support for the block. For example a brick and concrete prefabricated block with a continuous layer of concrete may be stronger and less permeable to water than a brick built wall

The mould may further include formers, which may be removable, that can be used to define voids, slots, apertures or other features in the cured block. For example at opposing ends of the mould there may be ridge formers that define a slot along the opposing ends such that the prefabricated block includes slots at each end.

The protrusions may be any suitable size, shape and configuration. The protrusions are preferably resiliently deformable as this -allows- the protrusions-to adjust to slight irregularities in the size and shape of the inclusion members and can aid with the formation of a seal to substantially prevent matrix from reacing the display face of the inclusion members. The protrusions are preferably elongate and are preferably fabricated as an extrusion and attached to the first mould face in the predetermined pattern. The resiliently deformable surface is preferably arranged between the protrusion and may also extend at least some way beneath the protrusions.

The protrusions and resiliently deformable surface layer may be integrally formed and the integral component adapted to substantially cover the first mould face. The protrusions are preferably raised from the surface of the integral component. However, the integral component may include a pattern visually indicating load sites and/or the integral component may include areas of more or less resiliently deformable material to denote the load sites, for example with more easily deformable material being the load site and the more resilient material, in use, forming protrusions. In such a case, the surface within a load site will compress slightly as an inclusion member is loaded into said site and by an increased amount as a force is applied to deform the layer and this will leave the protrusions adjacent the load site protruding. Such a component may be fabricated from, for

example, deformable foam or expanded polymer.

It should be noted that in the case of porous inclusion members such as bricks and a matrix which may suffer from 'drying out' the inclusion members may be initially wetted using water or other liquid to prevent them absorbing liquid from the matrix and thereby preventing the matrix from smoothly penetrating between the inclusion members.

It is preferred that the first mould face is substantially horizontal as the mould is filled with a matrix. The matrix is part cured, in the case of concrete, the concrete is first stage cured. This means that the concrete is allowed to cure for between 2 to 4 hours and preferably substantially 3 hours and the mould is then inverted so that the weight of the curing block rests upon the second mould face and the first mould face can be removed. The matrix is not fully cured at this stage so it is still slightly soft, but retains its shape. This means that the inclusion, members are retained in place and not substantially forced out of the block by the inclusion members as the first mould face is removed. The inverting at this early stage of curing helps to prevent any liquid matrix from seeping past the seal between the protrusions, deformable layer and the display face as such seepage could stain the display face. It should be understood that the mould may be inverted immediately after the second mould face has been used to substantially seal the mould, or at any time before removal of the first mould face, but that the first mould face will not be removed until after the partial curing has occurred. It is preferred that inversion of the mould occurs only after the partial curing has occurred as this reduces the likelihood that the inclusion members could move around during the inverting operation. The mould could be inverted using any suitable apparatus, such as cranes and the like, but a cradle could be fabricated allowing the mould to the inverted while attached to the cradle.

Any plastic sheet protecting the first mould face is then removed and the display faces of the inclusion members cleaned. The cleaning of the display faces preferably involves brushing the display faces with water. The water may include

a masonry cleaner additive. The brushing of the exposed face also has the advantage that, in its not fully cured state, the matrix that is to be visible between the inclusion members is roughened through contact with the brush and, for example when trying to create a brick wall effect finish, this is advantageous over the smooth finish that may otherwise be visible.

By not using the protrusions themselves to retain the inclusion members within the mould, the matrix can be allowed to penetrate further between the inclusion members so that the matrix substantially reaches the periphery of the display face. In the case of brick inclusion members, this substantially removes the need for the cured block to be hand pointed to protect the brick for weather damage.

The invention also provide a mould for use in the above -method, the- mould having side walls and a first mould face and a second mould face, the first mould, face including a resiliently deformable layer and further including a predetermined pattern of protrusions, the predetermined pattern of protrusions defining a plurality of load sites for receiving inclusion members, the protrusions being arranged to substantially surround a display face of an inclusion member.

The invention also provides a prefabricated block, the prefabricated block being formed from a cured matrix and a plurality of inclusion members, the prefabricated block having a core of cured matrix and having at least one face portion including the plurality of inclusion members, the plurality of inclusion members extending into, and secured to, the cured matrix, the cured matrix further including a least one insert contacting a surface of the inclusion members within the block.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which:

Figures 1a and 1b show a top and front view respectively of a prefabricated concrete block having half bricks moulded into a front face;

Figures 2a and 2b show a mould suitable for use in forming a pre-cast block similar to that of Figure 1 ;

Figure 3 shows a half brick;

Figures 4a and 4b show cross sectional views adjacent load sites being loaded with half bricks; and

Figure 5 shows a detailed cross section through a finished prefabricated block.

DETAILED DESCRIPTION

Figures 1a and 1b show a top and front view respectively of a prefabricated concrete block 1 having inclusion members, in this case half bricks 2, moulded into a front portion 4. The block has a rear portion 6 formed from a layer of concrete or reinforced concrete. The block 1 includes slots 8,10 in side faces 12,14 suitable for engaging with a protrusion from a secured beam or strut (not shown) to provide support for the block 1.

Figures 2a and 2b show different cross sections through a loaded mould 16. The view in 2b is a cross section through the mould along the line A-A shown in Figure

2a. The mould 16 comprises a first mould section 18 which includes a first mould face 20, a second mould section 22 which includes a second mould face 24 and

mould walls 26,28,30,32. These mould sections and walls together define a mould internal volume 34.

Within the mould internal volume 34 the first mould face includes a plurality of load sites 36 defined by protrusions 38 in a predetermined pattern. In this case the pattern is a brickwork pattern having a plurality of adjacent horizontal layers, with each adjacent layer being staggered by half a brick length. Each load site 36 is loaded with a half brick 2. A resiliently deformable metal strip 40 is located across a surface of the half brick opposite a display face 50 of the brick and pre-stressing wires 44 are arranged such that pre-tensioning of the wires 44 resiliently deforms the strips 40, thereby forcing the half bricks 2 into a deformable surface layer within the load sites (better shown in later figures). The mould interior volume 34 is filled with ^~ a matrix, , in this case -concrete before the -second mould -section 22 is secured to the walls.

Figure 2b shows that opposing walls 30 and 32 include prβr-stressing frames 46,48 for stressing the wires 44 within the mould so that a pre-stressed prefabricated block can be created. The wires 44 are stressed after the concrete has been poured into the mould 16 and the second section 22 attached to the walls 26,28,30,32.

Figure 3 shows a close-up view of a half brick 2 suitable for use in the mould 16 of Figures 2a and 2b. The half brick 2 is, in this case, a conventional brick that has been cut in half along its long axis of symmetry. The half brick 2 has a display face 50 defined by a periphery 52. The display face 50 is the face of the brick that would commonly be seen in a brick wall. The half brick of Figure 3 includes a recess 54 as a result of the shape of the original brick. Half bricks for use as inclusion members in the mould 16 could have any suitable shape as a result of the original brick shape or the inclusion member bricks could be fabricated specially for use in the mould.

Referring again to the mould 16 of Figure 2, when the load sites 36 are loaded

with half bricks 2 according to the method, the display faces 50 of the half bricks 2 are located adjacent the first mould face 20 and the protrusions 38 are located substantially around the periphery 52 of the display face 50. The half bricks 2 are arranged in the brickwork pattern of load sites 36 as defined by the sealing protrusions 36.

Figures 4a and 4b show cross sectional views adjacent load sites 36 and 36' separated by a protrusion 38 being loaded with half bricks 2.

The first mould face 20 is covered by a resiliently deformable foam rubber layer 54 through which protrusions 38 extend. The protrusions and deformable layer 54 are covered by a plastic sheet 37. The protrusions 38 in this case include a body portion -56 and wing ^{^} portions 58,60 which -are -adapted to resiliently flex towards the body portion 56 as a half brick is inserted into a load site 36 defined by protrusions 38. The protrusion 38 includes shoulders 62 which rest against the first mould face 20 to determine the amount by which the protrusion 38 protrudes- from the first mould face 20.

The protrusion 38 also includes a fixing portion 64 for securing the protrusion 38 in the desired location on the first mould face 20. The first mould face 20 is fabricated from a sheet of steel 66 and includes slots 68 through which the fixing portion 64 is forced. To force the fixing portion 64 through the slot 68, the fixing portion 64 is compressed. The fixing portion 64 expands once it has passed through the slot 68 to retain the sealing protrusion 38 in place. The fixing portion 64 includes a channel 70 into which an insert (not shown), in this case a metal bar, can be located to substantially prevent the fixing portion 64 from being deformed so that it would pass back through the slot 68 without the insert first being removed.

It should be noted that a top surface 72 of the protrusion 38 is curved such that the wing portions 58,60 are directed downwards from the body portion 56 towards the first mould surface 20.

Figure 4b shows load sites 36,36' loaded with half bricks 2 and shows the wing portions 58,60 of the protrusion 38 have been resiliently deformed against the body portion 56 and towards the first mould face by the half bricks 2. The resilient deformation of the wing portions 58,60 against the half bricks 2 substantially forms a seal around the periphery 52 the display face 50 of the half brick. The seal that prevents matrix from reaching the display face 50 is further enhanced by the subsequent step of forcing the brick into the deformable layer 54. Since the deformable layer is resiliently deformable, it deforms where the force is applied and effectively moulds to the shape of the display face 50, this therefore forms an additional seal to prevent the matrix from reaching the display face 50.

To ^~ fornra pre-cast block 1 , the mould 16 is initially ^~ prepared-by arranging the first mould section 18 and the walls 26,28,30,32 and arranging the first mould face 20 so that it is substantially horizontal. A plastic sheet 37 is then laid over the first mould face and half-bricks 2 are loaded into -the load sites 36 such -that their display faces 50 are substantially surrounded by protrusions 38.

Deformable strips of 'V profile metal 40 are them placed over the bricks so that all the bricks 2 are in contact with at least one of the strips 40. Pre-stressing wires 44 are then added and pre-tensioned so that the strips 40 are compressed between the bricks 2 and the wires 44. The compression of the strips 40 forces the bricks 2 towards the first mould face 20 and therefore compresses the deformable surface layer 54 so that it substantially moulds to the shape of the display face 50.

The bricks 2 are then saturated with water before self compacting concrete is poured into the mould 16 until it reaches the top of the walls 26,28,30,32. The second mould section 22 is then moved into place so that the second mould face 24 substantially seals the mould 16 to define a mould interior 34. The second mould section 22 is secured to the first mould section 18 so that the walls are secured in place. The pre-stressing wires 44 are then stressed. The concrete is then left to cure to a first stage of cure which takes about 3 hours.

After the initial partial curing of the concrete, the sealed mould is inverted so that the second mould face 24 is the lower mould face. The first mould section 18 is de-coupled from the mould 16 and removed to expose the display faces 50 of the half-bricks 2. The plastic sheet 37 is removed and the display faces 50 of the bricks cleaned by brushing the exposed face with water and then with a masonry cleaner.

The concrete is then left to fully cure and the pre-cast block 1 can then be removed from the mould 16 after the pre-stressing wires 44 have been cut. The facilitate removal from the mould, each wall 26,28,30,32 may be individually separable from the mould 16. Due to the presence of the stressed pre-stressing wires 44,ihe-pre ^;: fabricated-block is a pre-stressed block.

Figure 5 shows a detailed cross section through a finished prefabricated block 1. The block 1 comprises a core 70 of cured matrix 6 and has a plurality of inclusion members, in this case half bricks 2 located in one face 72. The matrix 6 extends between the half bricks 2 towards their display faces 50. The matrix 6 is recessed back from the display faces 50 due to the presence of the protrusions 38 during pouring and initial curing of the matrix. The matrix 6 between the half bricks has a curved profile similar to the protrusion 38 as the matrix is recessed further from the display faces in the middle of the gap 74 between the half bricks 2 than adjacent the half bricks 2. Within the core 70, the pre-stressing wires 44 and the deformable strips 40 are cured into the pre-cast block.

It should be understood that the invention has been described above by way of example only and that modifications in detail may be made without departing from the scope of the invention as described in the claims.