Welding reinforcement offers advantages over conventional tying. Welds provide rigid connections that do not work loose during handling of the reinforcement or placing of the concrete. They are particularly advantageous for pre-assembled reinforcement cages, such as for piles, diaphragm walls, columns and beams. However, all welding should be carried out under controlled, factory conditions and NOT on site without specific approval. Quality control of the process should be in accordance with the CARES Steel for the reinforcement of concrete scheme. Information can be found in the CARES Guide to Reinforcing Steels, Part 6, Welding of reinforcing steels, copies of which are available from CARES (www.ukcares.com).
One situation in which site welding MAY be permitted is as part of a repair procedure, where additional reinforcing steel is required to replace corroded or damaged bars. Here new steel may be welded to the ends of existing bars, as an alternative to exposing sufficient lengths of the old bar so that the new material can be lapped with it. A suitable quality control procedure must be in place, to ensure that the weld has adequate strength and that the heat generated does not damage the concrete.
The previous Standard for welding, BS 7123:1989 was superseded by BS EN ISO 17660 in 2006. This ISO was heavily influenced by European and international practice which in some instances does not reflect UK practice. In order to overcome this, BS 8548 was published in 2017 to bridge the gap between the ISO and UK practice.