Rehabilitation methodology

One of the major issues facing any consultant or owner of a structure suffering from chloride or carbonation induced corrosion is what form of repair to undertake. As we have seen from the previous sections there are coatings, sealants, membranes and enclosures, specialized patch repair materials, options for total or partial replacement, impressed current and galvanic cathodic protection, electrochemical chloride removal, realkalization, electro-osmosis and corrosion inhibitors. These can be applied to structures suffering different degrees of corrosion due to chloride attack or carbonation or a combination of these two. Each treatment will have implications for the future maintenance requirements, time to next major intervention and ultimate service life of the structure. 

The practical solution for most owners of individual corroding structures will be to take advice from a civil engineering consultant or corrosion specialist who has extensive experience of working on the durability problems of atmospherically exposed concrete structures. Advice may also be sought from materials suppliers and applicators about their own particular systems and a consensus will be reached about the most effective repair to the structure based on local knowledge, experience and availability of materials and systems. 

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Mouton J, Khamitzhanova G, Kudaibergenov S, Geckeler KE (2002) Proceedings of the international monitoring conference on development of rehabilitation methodology of the environment of the Semipalatinsk region polluted by nuclear tests. Semipalatinsk, Kazakhstan, 21-24 September 2002, p 25... 

Electrochemical techniques such as cathodic protection, chloride removal and re-alkalization are discussed in a separate chapter following this one. Rehabilitation methodology is discussed in Chapter 8 after discussion of the major rehabilitation techniques. 

If CP is the chosen rehabilitation methodology then the correct choice of anode is vital. For applications where the life is less then 20 years and suitable anodes are available, galvanic cathodic protection. For longer lives, impressed current systems are more likely to be suitable assuming that power is available and maintenance will be conducted. When it comes to individual anode choice then the Table in HA BA 83/02 summarizes the merits and limitations discussed in Section 7.3.1 to 7.3.7. 

SHRP The Strategic Highway Research Program. A 150 million research effort that spent about 10 million on corrosion of reinforced concrete bridges suffering from chloride induced corrosion. SHRP produced about 40 reports covering assessment, repair and rehabilitation methodology. All reports can be downloaded from the www.trb.org website... 

If cathodic protection is the chosen rehabilitation methodology then the correct choice of anode is vital. For non-marine applications the usual choice will be an impressed current system. If it is a wearing surface then coatings are usually excluded. This leads to the use of the conductive concrete anode or one of the titanium configurations in an overlay or titanium ribbons in slots. 

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