GB2158767A - Production of pressed concrete product - Google Patents

Abstract

A process for producing a surface-patterned pressed concrete product involves placing on a perforate mould plate having a relief-pattern on the surface thereof, a sheet of fine mesh gauze co-extensive with the mould plate surface, pouring a concrete mix into said mould and pressing to extract water therefrom.

Description

SPECIFICATION Production of pressed concrete product This invention relates to a method of producing pressed concrete product, namely a load bearing concrete paving slab, with a surface pattern.

Concrete paving slabs are manufactured by two distinct alternative processes. The simpler of the two is a simple casting process where a concrete mix is poured into a mould and allowed to harden. In the other process, concrete is poured into a mould and pressed in a hydraulic press to a pressure of around 2000 psi, to compact the concrete and squeeze out the water. The latter process produces high density slabs for heavy duty use, the former produces a relatively light weight product aimed mainly at the domestic market for use in paving areas which are notsubjectto heavy loading.

The simple casting process. is quite versatile in the surface patterning which can be produced simply by forming surface patterns on the face plate of the mould. The nature of the pressing process makes it rather less adaptable to the production of relief patterned slabs. In this process there is a top and bottom perforate plate between which the concerete is pressed. These plates are of thick steel plate with apertures of about i̇nch over more or less their whole surface to permit drainage of water during pressing. To prevent loss of cement from the concrete with the water, a sheet of rough filter paper is placed between each plate and the concerete. The product which is produced by this process has on its surface a multiplicity of surface protrusions left by the impression of the perforations of the plate.Any attempt to produce surface patterns on the slab is largely inhibited by the need for both plates to be perforate for removal of the water.

An object of this invention is to provide a process for producing a surface-patterned passed concrete product.

According to this invention there is provided a process for producing a surface-patterned pressed concrete product comprising placing on a perforate mould plate having a relief-pattern on the surface thereof a sheet of fine mesh gauze co-extensive with the mould plate surface, pouring a concrete mix into said mould and pressing to extract water therefrom.

It will be appreciated that in this process only one of the mould plates need be as defined, the other face can be of tradional configuration. In normal practice the bottom plate of the mould of an otherwise conventional slab pressing machine would be replaced as defined by this invention.

Preferably the said gauze is of metal wire, for example the type of gauze used in Fourdinier belts used in a paper-making process. Typically the mesh size will be between 35 mesh and 40 mesh. Plastic gauzes may also be used. A sheet of rough filter paper may be placed between the gauze and the concrete to suppress the surface impression made by the mesh of the gauze.

The process of this invention has been found particularly adaptable for the production of slabs having the surface appearance of riven stone. In making the mould plates a section of natural riven stone is dressed by a stonemason to produce the uniformity of thickness around the edges where the slab will abut adjacent slabs. A cast-iron or steel plate is then produced from the master pattern stone by conventional metal casting technology.

The following is a description of a pressing process of this invention by way of example.

The concrete mix used in this example had the following make-up: 3 parts winstone, 2 parts sand, 1 part cement plus artificial colouring to produce a natural appearance.

In a conventional slab-pressing machine, the bottom plate was replaced by a plate having a relief pattern resembling that of riven stone, having been produced in the manner described hereinabove.

The size of the mould can be varied but in this example was 3 feet x 2 feet and of sufficient depth to produce a final product two inches thick.

A sheet of metal wire gauze was placed in the mould atop the relief-patterned plate followed by a sheet of filter paper.

A load of 55 kg. of the aforesaid concrete mix was.

loaded into the mould.

The top plate of the press mould was of conventional type and a sheet of paper was placed atop the concrete mix in the usual way.

The mix was then subjected to a pressure of 2000 psi and water was extracted from above and below in the normal manner.

The final product had the appearance of a substantially smooth finish, save for almost indiscernible surface markings produced by the mesh and, of course, the relief pattern, riven stone slab.

Although, for simplicity of description, the invention has been described above in relation to a concrete slab which has one relief-patterned face, it is possible to use the invention to manufacture kerbstones or edging stones where more than one surface of the product carries the relief-patterning.

For example, for a kerbstone, the mould may comprise a bottom plate as described above and an upstanding edge plate engaged therewith in a simple L-shaped keyway. The top and other side plates are irrelevant. The assembly is lowered into a mould box, concrete mix poured in, and the product pressed as normal. As the pressed product is ejected from the mould box by raising the bottom plate, the side plate falls away (or can be knocked away) once it is clear of the top edge of the mould box.

1. A process for producing a surface-patterned pressed concrete product comprising placing on a perforate mould plate having a relief-pattern on the surface thereof, a sheet of fine mesh gauze coextensive with the mould plate surface, pouring a concrete mix into said mould and pressing to extract water therefrom.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (2)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Production of pressed concrete product This invention relates to a method of producing pressed concrete product, namely a load bearing concrete paving slab, with a surface pattern. Concrete paving slabs are manufactured by two distinct alternative processes. The simpler of the two is a simple casting process where a concrete mix is poured into a mould and allowed to harden. In the other process, concrete is poured into a mould and pressed in a hydraulic press to a pressure of around 2000 psi, to compact the concrete and squeeze out the water. The latter process produces high density slabs for heavy duty use, the former produces a relatively light weight product aimed mainly at the domestic market for use in paving areas which are notsubjectto heavy loading. The simple casting process. is quite versatile in the surface patterning which can be produced simply by forming surface patterns on the face plate of the mould. The nature of the pressing process makes it rather less adaptable to the production of relief patterned slabs. In this process there is a top and bottom perforate plate between which the concerete is pressed. These plates are of thick steel plate with apertures of about i̇nch over more or less their whole surface to permit drainage of water during pressing. To prevent loss of cement from the concrete with the water, a sheet of rough filter paper is placed between each plate and the concerete. The product which is produced by this process has on its surface a multiplicity of surface protrusions left by the impression of the perforations of the plate.Any attempt to produce surface patterns on the slab is largely inhibited by the need for both plates to be perforate for removal of the water. An object of this invention is to provide a process for producing a surface-patterned passed concrete product. According to this invention there is provided a process for producing a surface-patterned pressed concrete product comprising placing on a perforate mould plate having a relief-pattern on the surface thereof a sheet of fine mesh gauze co-extensive with the mould plate surface, pouring a concrete mix into said mould and pressing to extract water therefrom. It will be appreciated that in this process only one of the mould plates need be as defined, the other face can be of tradional configuration. In normal practice the bottom plate of the mould of an otherwise conventional slab pressing machine would be replaced as defined by this invention. Preferably the said gauze is of metal wire, for example the type of gauze used in Fourdinier belts used in a paper-making process. Typically the mesh size will be between 35 mesh and 40 mesh. Plastic gauzes may also be used. A sheet of rough filter paper may be placed between the gauze and the concrete to suppress the surface impression made by the mesh of the gauze. The process of this invention has been found particularly adaptable for the production of slabs having the surface appearance of riven stone. In making the mould plates a section of natural riven stone is dressed by a stonemason to produce the uniformity of thickness around the edges where the slab will abut adjacent slabs. A cast-iron or steel plate is then produced from the master pattern stone by conventional metal casting technology. The following is a description of a pressing process of this invention by way of example. The concrete mix used in this example had the following make-up: 3 parts winstone, 2 parts sand, 1 part cement plus artificial colouring to produce a natural appearance. In a conventional slab-pressing machine, the bottom plate was replaced by a plate having a relief pattern resembling that of riven stone, having been produced in the manner described hereinabove. The size of the mould can be varied but in this example was 3 feet x 2 feet and of sufficient depth to produce a final product two inches thick. A sheet of metal wire gauze was placed in the mould atop the relief-patterned plate followed by a sheet of filter paper. A load of 55 kg. of the aforesaid concrete mix was. loaded into the mould. The top plate of the press mould was of conventional type and a sheet of paper was placed atop the concrete mix in the usual way. The mix was then subjected to a pressure of 2000 psi and water was extracted from above and below in the normal manner. The final product had the appearance of a substantially smooth finish, save for almost indiscernible surface markings produced by the mesh and, of course, the relief pattern, riven stone slab. Although, for simplicity of description, the invention has been described above in relation to a concrete slab which has one relief-patterned face, it is possible to use the invention to manufacture kerbstones or edging stones where more than one surface of the product carries the relief-patterning. For example, for a kerbstone, the mould may comprise a bottom plate as described above and an upstanding edge plate engaged therewith in a simple L-shaped keyway. The top and other side plates are irrelevant. The assembly is lowered into a mould box, concrete mix poured in, and the product pressed as normal. As the pressed product is ejected from the mould box by raising the bottom plate, the side plate falls away (or can be knocked away) once it is clear of the top edge of the mould box. CLAIMS

1. A process for producing a surface-patterned pressed concrete product comprising placing on a perforate mould plate having a relief-pattern on the surface thereof, a sheet of fine mesh gauze coextensive with the mould plate surface, pouring a concrete mix into said mould and pressing to extract water therefrom.

2. A process as claimed in claim 1, in which the mould plate has an additional relief-patterned plate generally perpendicular thereto and releasably connected thus to provide a surface pattern on a pair of adjacent surfaces of the product.