ABSTRACT
Re-alkalisation and chloride extraction have maintained a significant share of the world market for concrete repair, and are attractive because they treat the causes of reinforcement corrosion (carbonation and chloride contamination) rather than just the symptoms (cracking, spalling and delamination). Used in conjunction with local patch repairs, where necessary, re-alkalisation re-establishes alkaline conditions in the cover zone and chloride extraction reduces the chloride concentration. These beneficial effects are counterbalanced by the increased risk of Alkali-Silica Reaction (ASR) resulting from the higher concentrations of alkali metal and hydroxyl ions. However, while Al-Kadhimi et al (1996a) found that re-alkalisation decreased ASR expansion, Page & Yu (1995) showed that there exists a pessimum amount of charge passed in the chloride extraction treatment at which expansion is greatest. This paper describes hitherto unpublished experimental work from a project completed in 1997 which aimed to resolve this disagreement in the observed ASR of concrete.
