Steel Mesh & Expanded Metal
Steel mesh and expanded metal can be used as permanent formwork, generally in vertical applications. The openings in the mesh must be sufficiently small (not greater than the largest aggregate size in the concrete) to retain the concrete, though there will be some grout loss. If the final surface is to be exposed it will require rendering or the application of some other surface layer.
Steel mesh or expanded metal can be an effective method of forming a stop end for a construction joint as the rough surface so formed requires no further preparation prior to the subsequent phase of casting. In this application it obviously gets rid of the requirement to remove traditional timber stop ends. Reinforcing bars, for continuity, can be easily installed through the mesh. The steel mesh or expanded metal permanent formwork will not provide any strength to the completed structure.
Mesh with larger openings can be used in foundation works such as ground beams. In this application, the mesh is covered with a layer of polyethylene sheeting on both faces. The resulting material is rather flexible and is generally supported by the backfill. The reinforcement cage must be sufficiently robust to support the pressures from the backfill until the concrete has gained sufficient strength.