Alkali-silica reaction (ASR) - Revision history

Designing Buildings at 09:06, 7 December 2020

2020-12-07T09:06:25Z

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	* The properties of concrete.		* The properties of concrete.

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213.104.196.50 at 10:33, 19 November 2019

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	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.		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 ~~hydroscopic~~ 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.	+	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 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.

Editor at 15:22, 4 July 2018

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	* Alkali-aggregate reaction (AAR).		* Alkali-aggregate reaction (AAR).
	* Cement.		* Cement.
		+	* Chert.
	* Concrete.		* Concrete.
	* Concrete superplasticizer.		* Concrete superplasticizer.

Designing Buildings at 09:01, 28 June 2018

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−	Alkali-silica reaction (ASR), commonly known as ‘concrete cancer’ is an expansive reaction that can ~~gradually~~ occur between aggregate constituents and alkaline hydroxides from cement. This can cause damage to the hardened concrete in a building, ~~such that it~~ can ~~demand~~ significant remedial works or even demolition.	+	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.		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 hydroscopic gel which expands ~~when absorbing~~ water, ~~thereby~~ imposing pressure on the surrounding concrete and weakening it in a way similar to ~~water in~~ freeze-thaw action. Cracking is a particular risk in ~~unrestrained~~ concrete~~, i.e. concrete without any reinforcement in it~~.	+	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 hydroscopic 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.

−	~~The occurrence of~~ ASR ~~is dependent on~~ the cement ~~having~~ a ~~sufficiently~~ high alkali content and there ~~being~~ a reactive aggregate such as chert. In addition, it requires ~~water and will not form if there is no~~ water in the 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.		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.

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Alkali-silica reaction (ASR), commonly known as ‘concrete cancer’ is an expansive reaction that can gradually occur between aggregate constituents and alkaline hydroxides from cement. This can cause damage to the hardened concrete in a building, such that it can demand 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 hydroscopic gel which expands when absorbing water, thereby imposing pressure on the surrounding concrete and weakening it in a way similar to water in freeze-thaw action. Cracking is a particular risk in unrestrained concrete, i.e. concrete without any reinforcement in it.

The occurrence of ASR is dependent on the cement having a sufficiently high alkali content and there being a reactive aggregate such as chert. In addition, it requires water and will not form if there is no 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.

= Find out more =

=== Related articles on Designing Buildings Wiki ===

* Alkali-activated binder.
* Alkali-aggregate reaction (AAR).
* Cement.
* Concrete.
* Concrete superplasticizer.
* Defects in construction.
* Laitance.
* Portland cement.
* Research on novel cements to reduce CO2 emissions.
* Spalling.
* Stratification of concrete.
* The properties of concrete.

[[Category:Health_and_safety_/_CDM]] [[Category:Construction_techniques]]