THE RE-ALKALISING PROCESS

This article describes the process of re-alkalisation, an electrochemical treatment that is used to halt and permamently prevent the corrosion of steel reinforcement in carbonated concrete. Re-alkalisation was developed by Norwegian Concrete Technologies in the early 1980s; it increases the pH of the carbonated concrete to a value greater than 10, which is sufficient to passivate steel permanently. In the process, a low voltage dc electric field is applied between the steel reinforcement (cathode) in the concrete and an externally mounted temporary electrode mesh (anode). The anode is embedded in a spray-applied cellulose fibre, wetted with an alkaline sodium carbonate solution that acts as the electrolyte. When electric power is applied, the alkaline solution is transported into the concrete by electro-osmosis; at the same time, electrolysis at the reinforcement surface produces hydroxyl ions to produce a very alkaline environment. The treatment is non-destructive, in the sense that only spalled, cracked, or honeycombed concrete need be repaired before applying it. After re-alkalisation, the concrete can be given a decorative finish. Two case studies of the successful use of the method for repair are described: (1) Desborough Water Tower, Northants, England; and (2) the Hoover Building on the A40 in West London.

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  • Corporate Authors:

    CEMENT & CONCRETE ASSOCIATION OF NEW ZEALAND

    13 WALL PLACE
    PORIRUA,   New Zealand 
  • Authors:
    • DARBY, M
  • Publication Date: 1993

Language

  • English

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00725449
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD
  • Created Date: Sep 26 1996 12:00AM