Alkali-silica reaction (ASR)
Alkali-silica reaction (ASR), commonly known as ‘concrete cancer’ is an expansive reaction that can occur over time between aggregate constituents and alkaline hydroxides from cement. This can cause damage to the hardened concrete in a building, and can necessitate significant remedial works or even demolition.
ASR is the most common form of alkali-aggregate reaction (AAR) in concrete. Another, less common, form is alkali-carbonate reaction (ACR). For more information, see Alkali-aggregate reaction.
The primary cause of ASR is a reaction between the alkaline cement’s hydroxyl ions and some aggregate’s reactive forms of silica. This produces a hygroscopic gel which expands on the absorption of water, imposing pressure on the surrounding concrete and weakening it in a way similar to a freeze-thaw action. Cracking is a particular risk in unreinforced concrete.
ASR can occur when the cement has a high alkali content and there is a reactive aggregate such as chert. In addition, it requires the presence of water in the concrete.
ASR is best detected by examining concrete in thin sections using a microscope, as the gel may be present in cracks and within aggregate particles. Techniques that can be adopted to try and reduce the likelihood of ASR include the use of low-alkali Portland cement, and the introduction of pozzolans to the concrete mix. The addition of pozzolans reduces the alkalinity of the pore fluid as the amount of cement in the mix is lowered.
[edit] Find out more
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
Listed despite problems with its design.
Zen and the art of cycling exploration.
Design Council Homes Taskforce launched
To support government 1.5 million homes target within UK climate commitments.
The story of this knowledge quarter building.
In ecology, in hydrology, in biology and in architecture.
Creating environments that promote physical, mental, and social well-being.
UK cases of neutral current diversion
Research project looks for example contributions.
Overstocking and macro-economics cause a decline.
The 2024 update of the Common Assessment Standard
Demonstrating organisational capability’ to fulfil roles under the Building Safety Act.
56 recommendations for a better built environment
Published by the CIC ahead of the King’s Speech.
SkillELECTRIC Top 8 Competitors Named
in annual search for the UK’s best student electrician.
CIOB Diversity and Inclusion technical information sheet
Step-by-step guide on implementing D and I practices.
Conservation and the Indian City. Book review.
Reversibility in conservation ethics
Learning from painting conservation.
Where It's AT Podcast launched!
New CIAT Architectural Technology Podcast goes live.