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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.
Alkali–carbonate reaction. The alkali–silica reaction is the most common form of alkali–aggregate reaction. Two other types are: the alkali–silicate reaction, in which layer silicate minerals (clay minerals), sometimes present as impurities, are attacked, and; the alkali–carbonate reaction, which is an uncommon attack on certain ...
This reaction is at the core of the alkali–silica reaction (ASR): 2 NaOH + SiO 2 → Na 2 SiO 3 · H 2 O. Following this reaction, a hygroscopic and expansive viscous silicagel phase forms inside the affected aggregates which swell and crack from inside. In its turn, the volumetric expansion of the swollen aggregates damages the concrete ...
Alkali–carbonate reaction; Alkali–silica reaction; Amorphous silica-alumina; Andrussow process; Anthraquinone process; Applied Catalysis Award; Asymmetric catalytic oxidation; Asymmetric counteranion directed catalysis; Asymmetric ion-pairing catalysis; User:Athel cb/sandbox; Autocatalysis
Dicalcium silicate, which reacts more slowly, only contributes to late strength. Calcium silicate hydrate (also shown as C-S-H) is a result of the reaction between the silicate phases of Portland cement and water. This reaction typically is expressed as: 2 Ca 3 SiO 5 + 7 H 2 O → 3 CaO · 2 SiO 2 · 4 H 2 O + 3 Ca(OH) 2 + 173.6 kJ
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The alkali–silica reaction (ASR) causes localised swelling responsible for tensile stress and cracking. The conditions required for alkali silica reaction are threefold: (1) aggregate containing an alkali-reactive constituent (amorphous silica), (2) sufficient availability of hydroxyl ions (OH − ), and (3) sufficient moisture, above 75% ...
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