What does AAR mean in UNCLASSIFIED
Alkali Aggregate Reaction, or AAR, is a type of chemical reaction that occurs between certain types of aggregates used in concrete and the alkalis present in cement. This reaction can cause significant damage to concrete structures over time. The purpose of this article is to provide a basic introduction to AAR and answer some frequently asked questions.
AAR meaning in Unclassified in Miscellaneous
AAR mostly used in an acronym Unclassified in Category Miscellaneous that means alkali aggregate reaction
Shorthand: AAR,
Full Form: alkali aggregate reaction
For more information of "alkali aggregate reaction", see the section below.
Essential Questions and Answers on alkali aggregate reaction in "MISCELLANEOUS»UNFILED"
What are alkalis?
Alkalis are substances that are basic in nature, i.e., they have a pH higher than 7.0. Common examples include sodium hydroxide, potassium hydroxide and calcium hydroxide.
What type of aggregate materials can cause AAR?
Certain siliceous and carbonaceous materials are prone to react when exposed to alkali solutions, causing expansion of the aggregate material. These reactive materials can cause significant damage if used in concrete structures with high levels of alkalis.
How can I tell if my concrete structure has AAR?
Signs of AAR include cracking, scaling and spalling (flaking away) of the concrete surface as well as efflorescence (white powdery deposits on the surface). Additionally, laboratory testing should be performed to measure alkalis and soluble silica content in samples taken from the structure under investigation.
Does adding admixtures help prevent AAR?
Some admixtures can be used in combination with other measures such as redesigning or substituting non-reactive aggregate materials, applying protective coatings or using low-alkali cements to reduce the potential for AAR occurring within a concrete structure.
How does heat help prevent AAR?
Heat curing may also be beneficial for controlling alkali silica reactivity. Heating accelerated cement hydration processes and results in lower available calcium hydroxide concentrations within the hardened paste which helps reduce potential expansive reactions from occurring later on.
Final Words:
Alkali Aggregate Reaction has the potential to cause serious damage to concrete structures over time if not managed properly. Careful selection of aggregates and proper curing techniques are key components for preventing AAR from occurring in concrete work since this type of reaction cannot be cured after it has already occurred.
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