AU1839501A - Improved reinforcing mesh - Google Patents

Description

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AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT 0 0 0 0 0*00 0 0 0000 Name of Applicant: Actual Inventors: Address for Service: Invention Title: Neumann Steel Pty Ltd Christopher Anning Brian Clive Wade CULLEN CO., Patent Trade Mark Attorneys, 239 George Street, Brisbane, QId. 4000, Australia.

Improved Reinforcing Mesh Details of Associated Provisional Applications: Australian Patent Application No.

PQ5587 filed 11 February 2000 The following statement is a full description of this invention, including the best method of performing it known to us:

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2 IMPROVED REINFORCING MESH This invention relates to an improved mesh for reinforcing concrete. The invention is particularly, but not solely, directed to an improved steel mesh for reinforcing subterranean walls in mines. However, it will be appreciated by those skilled in the art that the mesh of this invention has wider application.

BACKGROUND ART It is known to use a "double" mesh to reinforce concrete walls in tunnels, mines and other subterranean applications. The known double mesh consists of a first steel mesh formed by a grid of longitudinal rods and cross rods welded together at their junctions. The rods are about 5mm in diameter, and the spacing between the longitudinal rods and the cross rods is about 150mm.

15 The 150mm square apertures in the first mesh are infilled with a second mesh of finer construction. The second mesh is a woven mesh of fine longitudinal and cross wires of 0.45mm in diameter with inter-wire spacing of 3mm.

The first mesh is a self-supporting mesh which, in use, can be 20 arranged against an excavated earth wall or the like to provide reinforcing for a concrete wall formed around the mesh against the excavated wall. This wall is normally formed by spraying grout against the excavated wall and over the mesh. The first mesh supports the second mesh in the desired configuration.

The second, finer, mesh provides greater surface area to which the sprayed grout can adhere.

Although the above described "double mesh" (also known as Mine Mesh or Vent Mesh) performs satisfactorily, it has been found that surprisingly better performance can be obtained by changing the size of the apertures in the second mesh.

It is therefore an object of this invention to provide an improved mesh particularly, but not solely, for use in sprayed concrete walls.

SUMMARY OF THE INVENTION In one broad form, this invention provides a reinforcing mesh, comprising a first grid formed from longitudinal and cross rods, and a second grid, supported by the first grid, and formed from longitudinal and cross wires of smaller diameter than the rods, characterised in that the spacing between adjacent wires of the second grid is between 1.5mm and That is, the spacing between adjacent longitudinal wires (the aperture width) is between 1.5mm and 2.5mm, and the spacing between adjacent cross wires (the aperture length) is between 1.5mm and Preferably, the spacing between adjacent wires of the second grid is 2mm i.e. the second grid is a fine mesh of approximately 2mm square apertures.

Typically, the first grid has apertures of 150mm square, and is formed from hard drawn steel rods of 3-5mm diameter. The longitudinal and •cross rods are welded together at their junctions. However, the size of the rods and apertures of the first grid can be varied to suit the particular application.

The outer longitudinal rods, and/or the outer cross rods, of each mesh panel may be spaced closer together than those in the center of the panel.

The second grid is typically a woven mesh of longitudinal and cross wires having a diameter of around .045mm. The diameter of the fine mesh wires may be varied to suit.

Ithas been found thaLwth_-cQnvefntiQal-3mm mesh infill, a significant portion of the filler or grout material sprayed onto the mesh passes through the mesh. Several coats or passes may be required in order to obtain the required minimum bond. However, with a 2mm mesh infill, one spray application is sufficient to provide adequate coverage and bonding to the fine mesh. The fine mesh allows the grout material to wrap around both sides of the mesh giving good adhesion.

The 2mm mesh allows less "blow through", i.e. less material passes straight through the mesh without bonding to the mesh.

Consequently, less grout material is used. If the mesh is being used in a mine or other subterranean environment, a further advantage is that less grout or filler material need be taken down the mine.

The 2mm mesh has been found to be the optimum in terms of performance and cost although a range of 1.5mm to 2.55 is acceptable. If the mesh were to be made of smaller aperture than 1.5mm, the cost would increase substantially due to the additional steel material required. If the mesh aperture were to be increased beyond 2.5mm, more grout or filler would be used due to the "blow through" effect.

In order that the invention may be more fully understood and put into practice, an embodiment thereof will now be described with reference to o the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an underside view of a mesh according to a preferred embodiment of the invention, and o Fig. 2 is a fragmentary top perspective view of the mesh of Fig.

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DESCRIPTION OF PREFERRED EMBODIMENT As shown in Figs. 1 and 2, a mesh 10 of the "mine mesh" type comprises a first grid or mesh formed of longitudinal rods 11 and cross rods 12 which are typically hard drawn steel rods of 3-5mm diameter, welded together at their junctions or crossover points. The spacing between the longitudinal and cross rods is typically 150mm.

However, the spacing between the outer rods may be less than the spacing between the rods in the center of the mesh panel. In the illustrated embodiment, the spacing between the outermost pair of longitudinal rods is 40mm and the spacing between the next outermost pair of longitudinal rods is A second mesh 13 is fixed to the steel grid formed from rods 11, 12 e.g. by welding or other suitable means. The mesh 13 is a fine woven mesh of longitudinal and cross wires, typically of 0.45mm diameter, with an inter-wire spacing of 2mm, with 10% tolerance. The mesh 13 may be a steel wire mesh, or made of any other suitable material. The fine mesh 13 covers or fills the 150mm square apertures in the larger mesh.

In use, the mine mesh 10 is located adjacent an excavated wall, and can be bent to suit the curvature of the wall. The fine mesh 13 is supported in the desired configuration by the stronger self-supporting grid formed from rods 11,12. Grout or other filler material can then be sprayed against the mesh to adhere thereto and build up into a wall of desired thickness.

foregoing describes only one embodiment of the invention, and modifications which are obvious to those skilled in the art may be made 15 thereto without departing from the scope thereof.

For example, a fine mesh with an aperture less than 2mm may •be used in applications other than in mines.

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Claims (12)

1. A reinforcing mesh, comprising a first grid formed from longitudinal and cross rods, and a second grid, supported by the first grid, and formed from longitudinal and cross wires of smaller diameter than the rods, characterised in that the spacing between adjacent wires of the second grid is between 1.5mm and

2. A reinforcing mesh as claimed in claim 1, wherein the spacing is approximately

3. A reinforcing mesh as claimed in claim 1 or 2, wherein the wires of the second grid have a diameter of approximately 0.045mm.

4. A reinforcing mesh as claimed in any preceding claim wherein the first grid is formed from longitudinal and cross rods having a diameter between 3 and 5mm, and forming apertures of approximately 150mm square. 15

5. A reinforcing mesh as claimed in any preceding claim wherein the second grid is fixed to the first grid by welding.

6. A reinforcing mesh as claimed in any preceding claim, wherein the spacing between adjacent longitudinal rods of the first grid is smaller at the sides of the grid than in the centre of the grid. o 20

7. A reinforcing mesh as claimed in any preceding claim, wherein the spacing between adjacent cross rods of the first grid is smaller at the sides of the grid than in the centre of the grid. o* o

8. Reinforcing for concrete walls, comprising a first self-supporting steel mesh, a second steel mesh fixed to the first mesh and supported thereby in use, the second mesh having apertures between 1.5mm and square.

9. Reinforcing as claimed in claim 8, wherein the apertures are approximately 2mm square.

Reinforcing as claimed in claim 8 or 9, wherein the first mesh is in the form of a grid formed from longitudinal and cross rods joined at their cross over points, the spacing between adjacent longitudinal rods and the spacing between adjacent cross rods being approximately 150mm in the central region of the grid.

11. Reinforcing as claimed in claim 10, wherein the spacing between adjacent longitudinal rods and/or adjacent cross rods is less at the edge of the grid than in the centre thereof.

12. Reinforcing mesh substantially as hereinbefore described with reference to the accompanying drawings. DATED this ninth day of February 2001 NEUMANN STEEL PTY LTD By their Patent Attorneys Cullen Co.