Managing the effects of alkali aggregate reaction on the concrete at Dinas dam, UK

The Dinas arch gravity dam was constructed in the early 1960s, and alkali aggregate reaction (AAR) in the concrete was confirmed in the late 1980s. The resulting concrete expansion has caused the crest to rise and the curved dam to tilt upstream, with downstream lift joints opening, one significantly. Recent concrete coring and testing has revealed the AAR to be variable in the dam body, but also that the reaction now appears to have effectively ceased. Surveys have also confirmed this. In-situ stress testing has revealed changes to the stress patterns in the dam, but with values well within acceptable limits.