Eliminating Alkali-Aggregate Reaction from long-service structures

RILEM has developed a testing and specification system to minimise AAR damage risk in new concrete structures. A performance test is being developed for particular mixes, usable on a project-specific basis; the challenge is proving a consistent relationship between test and field behaviours. Long-service structures, including dams, can sometimes exhibit progressive AAR, despite meeting criteria that usually prevent damage. Moreover, slow reactions can continue inexorably in large dam structures, gradually threatening integrity and serviceability. RILEM is working with ICOLD to ensure preventative schemes are effective with dams. Over an extended life, reactive alkalis are extracted from aggregates. A new "releasable alkalis" test is being validated by RILEM. Usually unpopular but more reliable long-term expansion tests are more practicable with long-service structures than smaller projects, including assessing the influence of SCMs. An improved RILEM specification scheme is introduced, aimed at eliminating the AAR risk in future longservice structures, including dams.