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
Extended reality in a post-pandemic world.
Can XR technology be leveraged in design & construction?
Or are you capping.
STEM ambassadors needed for ICE CityZen award.
Digital gaming competition for UK students aged 16 to 18.
Heritage protection in England vs Australia.
Fire doors and the Fire Door Inspection Scheme.
Three-quarters of fire doors fail inspections
UN International Day for Biological Diversity, May 22.
The role of geoparks, biospheres and world heritage sites.
BSRIA conference 2022, June 23.
Just one month to go ! Find out more here.
Restoring Broadbent’s Bath House
A new gallery for the University of Huddersfield.
Corruption in the construction industry.
What will it take to stop it ?
To celebrate world bee day 2022 !
Just one month until the changes to part L come into effect.
Not forgetting part F and the new part overheating part O.
Heat Pump demand rises by one quarter.
As energy prices jump up in cost.
With people in the UK from Ukraine.
Industry leader Steve Murray takes on role.
An abundant and versatile building material.
How overheating complicates ending gas in the UK.
600,000 heat pump installations targeted per year by 2028.
Cost planning, control and related articles on DB.
Helping prevent those unwanted outcomes.
ICE debate Public transport - post pandemic.
How has transport changed due to Covid-19 ?
Cross-ventilation in buildings. Do you have it ?
Will you need it ? after June 15 and the new Part O ?
Share your knowledge with the industry.
Create an account and write the first of many articles.
The green jobs delivery group.
CIAT commentary after the first meeting.
Liverpool's world heritage site status
Who is to blame?
Research recommends focussing on portfolio success rather than project success.