ABSTRACT
The inspection, maintenance and repair of concrete structures absorb a considerable volume of the construction budget in the UK and elsewhere. In Europe it has been estimated that it is some 50 per cent of the total and in the United States the annual expenditure due to corrosion of reinforcement alone amounts to some 8.3 billion dollars. Moreover, in extreme cases of deterioration there have been structural collapses (Doyle, 1993, Oliver, 2000, Government of Quebec, 2007). In consequence of these problems it has been recognised that concrete structures must be more durable in the first place and repairs must be effective.Repairs to damaged or defective concrete have been the subject of much research at academic institutes and in the repair industry. The professional institutions and code-writing bodies have published state-of-the-art advisory documents and guidelines to inform the workforce and raise the quality of repair work. The construction industry has developed improved materials and techniques to enable repairs to be more effective and durable in the long term. Unfortunately these efforts have not been entirely successful as it is generally found that the performance of concrete repairs is rather disappointing. It has been difficult to express performance quantitatively as there have been few surveys of repairs and those that have been reported have been either localised or lacking in sufficient detail or numbers to enable useful conclusions to be drawn. Surveys of structural condition are fairly common and have usually been carried out in response to concern about a particular condition (Radic, 1989, Rowe et al., 1984, Van Begin, 1987). Reports on the durability of repairs are usually based on laboratory work whereas fieldwork is much less common. In an overview of the durability of repair materials Cusson and Mailvaganam (1996) noted that: The lack of comprehensive data on the performance of repair products and on the potential incompatibility between repair materials and substrate concrete is at least partly responsible for the large number of premature repair failures in North American concrete structures.
