- Project plans
- Project activities
- Legislation and standards
- Industry context
Last edited 21 Nov 2018
Alkali-aggregate reaction (AAR)
However, the material had a 'guilty secret' that was only revealed by research in the USA during the 1930s. In some circumstances, an expansive reaction can gradually occur between aggregate constituents and alkaline hydroxides from the cement, causing damage to the hardened concrete within structures.
This has become known as 'alkali-aggregate reaction' (AAR), or most commonly and more specifically, 'alkali-silica reaction' (ASR). This AAR family of mechanisms is by no means the most frequently encountered threat to concrete durability or the serviceability of structures, but it can be a serious issue when it occurs.
 Getting to grips with AAR
Over more than 40 years, I have been privileged to witness practising engineers and applied scientists getting to grips with AAR worldwide. I believe we now understand the several reactions, including how to recognise them in existing structures and manage the situation, but crucially also including how to determine any possible AAR potential in new works and take effective precautionary measures.
However, challenges remain, especially as appreciation of the potential threat from AAR is not universally or equally appreciated everywhere in the world, and we are still finding types of structure that behave exceptionally. Overall, the prospects are encouraging for both a declining incidence of AAR damage and successful approaches to management and/or repair of affected cases.
This article was originally published by ICE on 30 June 2016. It was written by Simon Fullalove. You can see the original article here.
 Related articles on Designing Buildings Wiki
Featured articles and news
Cutting-edge tech pairs with building management systems.
BSRIA updates its assessment of the industry.
What happens when it all goes wrong?
Input being gathered by CIOB.
Changes proposed for MHCLG consultation on house building statistics.
Full of passion and acerbic wit. 1 min book review.
Reminding us what is possible.
Five signs you are at risk.
Biotechnology as it applies to the built environment.
Stopping sound coming through windows.
Government response to the Building a Safer Future consultation.
Energy savings quickly payback any small additional capital investment.
Overbuild and air-space developments.