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The alkali–silica reaction (ASR), also commonly known as concrete cancer, [3] is a deleterious internal swelling reaction that occurs over time in concrete between the highly alkaline cement paste and the reactive amorphous (i.e., non-crystalline) silica found in many common aggregates, given sufficient moisture.
Example of flat piece of concrete having dislodged with corroded rebar underneath, Welland River bridge across Queen Elizabeth Way in Niagara Falls, Ontario. The expansion of the corrosion products (iron oxides) of carbon steel reinforcement structures may induce internal mechanical stress (tensile stress) that cause the formation of cracks and disrupt the concrete structure.
Alkali–silica reaction (ASR), also known as alkali-aggregate reaction (AAR), when reactive amorphous silica aggregates exposed to alkaline conditions (high pH) swell inside the concrete matrix leading to the development of a network of cracks. It may also refer to:
Concrete sealers are applied to concrete to protect it from surface damage, corrosion, ... (ASR), chemical intrusion, and corrosion of steel reinforcements.
Alkali–aggregate reaction is a term mainly referring to a reaction which occurs over time in concrete between the highly alkaline cement paste and non-crystalline silicon dioxide, which is found in many common aggregates. This reaction can cause the expansion of the altered aggregate, leading to spalling and loss of strength of concrete.
A fairly well-defined reaction front can often be observed in thin sections; ahead of the front the concrete is normal, or near normal. Behind the reaction front, the composition and the microstructure of concrete are modified. These changes may vary in type or severity but commonly include: Extensive cracking; Expansion
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It is also used in ceramics and some Portland cement formulations, where it is also used to suppress ASR (concrete cancer). [16] Lithium hydroxide (isotopically enriched in lithium-7) is used to alkalize the reactor coolant in pressurized water reactors for corrosion control. [17] It is good radiation protection against free neutrons.