A large misunderstanding of the functions of fabric in preserving the life of concrete can be seen in cracked sidewalks and driveways around the country. The basic reason why a steel reinforcing material such as welded wire fabric is needed in a concrete ground slab is because concrete has little resistance to tension. By adding fabric to the slab, you add tensile strength, since steel is extremely strong in tension. Therefore, when the slab shrinks or contracts or when it is subject to the pulling, crack producing forces caused by twisting or warping, the steel resists these tensile stresses, distributing them evenly over a large area and helping it to hold tightly together minimizing cracks. The use of the material has sometimes proved a stumbling block to contractors. Welded wire fabric is easily cut with ordinary wire cutters and may be positioned in plastic concrete in one of three ways. The first method is to place the concrete about one half the desired slab thickness, strike off, then place the reinforcement and a second course of concrete without delay so that the courses bond together completely. A second method eliminates the need for two pours by placing piles of ready mix every three to five feet about the prepared sub-grade and then place the fabric across these piles. A variation of this is to have brickbats of the proper height placed about the sub-grade before the ready mix truck arrives. Thorough vibration or rodding of the plastic concrete is recommended in order to be sure that the mix is distributed completely and that the fabric is properly embedded all around, so that it can best perform its function of adding tensile strength to the finished slab.
