Patent Publication Number: US-4647515-A

Title: Reinforcing material

Description:
This invention concerns a reinforcing material for use in a ferrocement structure. 
     A commonly used fabric of steel for use in a ferrocement lay up includes a primary component comprising a plurality of parallel spaced rods in each of two directions at right angles to one another, the rods being welded together at their crossing points. To give more even distribution of steel and strength in other directions, such fabric is overlaid with a secondary component comprising a sheet of wire mesh fabric such as so-called chicken wire for example and the two layers are wired together to form a composite sheet. Often several layers of such composite sheet are overlaid and wired together to form the final reinforcing element which is to be embedded in the mortar. 
     Producing such composite sheets and reinforcing elements is clearly very labour intensive whether under factory conditions or on site. 
     It is an object of the present invention to provide a reinforcing material and method of making same which overcomes at least to some extent the problem aforesaid. 
     According to the present invention there is provided a mat of reinforcing material for use in the production of a ferro-cement structure and having a first layer comprised by spaced steel rods or wires, a second layer comprised by spaced steel rods of wires, the rods or wires of the first layer being at an angle to those of the second layer, and a plurality of further layers of wire mesh fabric disposed between the rods or wires of the first and second layers which are welded together at their crossing points to secure the further layers therebetween. 
     The invention also includes a method of making the reinforcing mat aforesaid and ferro-cement structures embodying such mats. 
    
    
     The invention will be further apparent from the following description, with reference to the several figures of the accompanying drawings, which show, by way of example only, one form of reinforcing mat embodying the invention constructed in accordance with the method thereof. 
     Of the drawing: 
     FIG. 1 shows a plan view of the mat; 
     and FIG. 2 shows a cross-section through the mat on the line II--II of FIG. 1. 
    
    
     Referring now to the drawing, it will be seen that the reinforcing mat comprises a layer of spaced parallel longitudinally extending rods 10 and a layer of spaced parallel cross rods 11 at right angles to the rods 10 with a plurality of layers of woven wire mesh fabric 12 such as so-called chicken wire disposed between the rods 10 and rods 11 such that the crossing points between the rods 10 and rods 11 do not overlie the wires of the layers of fabric 12. The rods 10 and 11 are welded together at their crossing points to secure them together and the layers of fabric 12 in position therebetween. 
     Generally there will be four or even more layers of the fabric 12, though the use of as few as two is possible and such is shown in the drawings, though in the interests of clarity only a fragment of the second layer of fabric is shown. The several layers, whatever their number, are laterally and longitudinally displaced or superimposed in offset relationship whereby the total wire content in the layers 12 is distributed over the total area of the mat substantially as evenly as possible, consistent with the requirement not to have wire between the rods 10 and 11 at their crossing points. 
     Typical spacings between adjacent rods 10 and adjacent rods 11 will be between 3 inches (7.6 cm) and half an inch (1.3 cm) and the spacing between the rods 10 may be different from that between the rods 11. The rods 10 and 11 may be of square or circular section and of desired gauge, typically from 8 to 22 swg. 
     Generally the gauge of the rods 10 and 11 will be no more than one gauge up or down on the gauge of the wire from which the mesh fabric 12 is formed and the mesh size of the fabric 12 will generally lie between 1 inch (2.54 cm) and half an inch (1.3 cm) though variations from these recommendations are possible, especially for particular design applications. 
     Since it is intended that one or more thicknesses of the mat of the invention will be the only reinforcement provided in a ferro-cement structure, the total content of reinforcing material, that is the rods 10, rods 11 and wire in the layers of fabric 12 will occupy at least 8% of the superficial volume of the mat. 
     The mats can be cut and bent to form ribs, arches, domes or any other shape to correspond with the shape of a ferro-cement structure to be produced. 
     The mat is produced by continuous stepped feed of the rods 10 from reels thereof along with the required number of layers of woven wire mesh fabric in superimposed relationship over a machine bed. After each step the cross rods 11 are fed onto the bed from the side to cross the rods 10 beneath welding heads which are then lowered to engage the rods 11 and deform them to contact the rods 10 when the heads are actuated to make the welds. The cross rods 11 may be fed and welded one at a time or in groups. 
     Materials embodying the invention have a tighter than conventional construction giving an increased density of steel, and the corrugated formation of the rods 11 gives added strength. 
     It will be appreciated that it is not intended to limit the invention to the above example only, many variations, such as might readily occur to one skilled in the art, being possible, without departing from the scope thereof as defined by the appended claims. 
     Thus, for example, secondary rods or wires may be incorporated along with the wire mesh fabric between the rods 10 and the rods 11. 
     Again, for example, the rods 10 and the rods 11 need not always be parallel with one another and the two sets need not cross at right angles.