Welded Wire Fabric (WWF), commonly Welded Mesh, is a prefabricated reinforcement consisting of parallel series of wires having a very high yield (Fe-480). The wires are cold drawn or cold-rolled, welded together in square or rectangular grids. Each wire intersection is electrically resistant – welded continuously by an automatic welding machine.
Welded Wire Mesh is bonded to concrete by a positive mechanical anchorage at each intersection.
Benefits of Welded Wire Fabric:
I. Controlled Manufacture
Weldmesh is manufactured from hard drawn steel wire and thus has a tensile strength not less than 580 N/mm2 while the tar steel used in traditional construction maybe as low as 250 N/mm2
II. Proper Distribution of Steel
Weldmesh provides equal distribution of steel reinforcement within the concrete slabs, affecting the strength. The number of small diameter wires spread across the cross section help in arranging the concrete slabs according to the specification.
III. Better Anchorage/Bond
Since the HYSD bars are tied with barbed wire at the intersection, they tend to be loose and shifty whereas a weldmesh sheet is strong in its intersection and rarely falls apart.
IV. Better Crack Resistance
o Research into crack width and the width prediction formulae adopted by the building cost show the maximum widths are propotional to the distance from the surface to the closest reinforcement i.e. to bar spacing and concrete cover and the inter reinforcement spacing.
o Weldmesh is much superior in restricting the crack width to acceptable limits in concrete slabs because of smaller diameter of wire used, closer and with uniform spacing.
o Thinner wire with closer spacing is efficient in ensuring more homogenous 2-way stress distribution throughout the concrete volume thereby controlling crack propagation as well as the crack width.
V. Easily Handled and Placed
Being welded automatically at joints, little labor is required for placing and fixing. When properly supported it remains fixated in its position during concretization.
VI. Adaptable For Forming And Shaping
Weldmesh possesses the right degree of ductility to allow it to be bent, shaped or fashioned readily on the job, yet it is sufficiently rigid to maintain its shape after bending.
VII. Higher Characteristic Strength
Use of Weldmesh with Fe-480 grade results in savings in steel area or steel weight required to the tune of 15% vis-à-vis HYSD bars of Fe-415 grade and to the tune of 47.92% vis-a-visplain mild steel bars of Fe-250 grade.
VIII. Better Corrosion Strength
Welded Wire Mesh, with thinner wires at closer spacing and more concrete cover, has relatively smaller cracks restricting the ingress of moisture and air to steel.