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The alkali–carbonate reaction is an alteration process first suspected in the 1950s in Canada for the degradation of concrete containing dolomite aggregates. [1] [2]Alkali from the cement might react with the dolomite crystals present in the aggregate inducing the production of brucite, (MgOH) 2, and calcite (CaCO 3).
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 ...
Often the alkali–silicate reaction and the dedolomitization reaction are masked by a much more severe alkali–silica reaction dominating the deleterious effects. Because the alkali-carbonate reaction (ACR) is often thwarted by a coexisting ASR reaction, it explains why ACR is no longer considered to be a major detrimental reaction.
The reaction of magnesium carbonate with the free alkali hydroxides present in the cement porewater also leads to the formation of expansive brucite. MgCO 3 + 2 NaOH → Mg(OH) 2 + Na 2 CO 3. This reaction, one of the two main alkali–aggregate reaction (AAR) is also known as alkali–carbonate reaction.
Alkali-aggregate reactions (AAR), both alkali-silica (ASR) and alkali-carbonate (ACR, involving dolomite) reactions, were identified in Canada since the years 1950's. [ 68 ] [ 69 ] [ 70 ] Many hydraulic dams are affected by ASR in Canada because of the wide use of reactive aggregates. [ 71 ]
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
Alkali–carbonate reaction; Alkali–silica reaction; Ammoxidation; Anaerobic glycolysis; Antigen retrieval; Arrow pushing; Associative substitution; Asymmetric ...
For pH control, popular chemicals include calcium carbonate, calcium oxide, magnesium hydroxide, and sodium bicarbonate. The selection of an appropriate neutralization chemical depends on the particular application. There are many uses of neutralization reactions that are acid-alkali reactions. A very common use is antacid tablets.