The alkali silicic acid reaction (short AKR) or also only alkali reaction and/or "alkali driving", populist also concrete cancer is the name for the chemical reaction between alkalis of the hardened cement paste in the concrete and concrete impacts with silicic acid soluble in alkali.

Concrete may not contain considerable quantities of harmful components. This among other things concrete impacts with silicic acids soluble in alkali can be, which in damp environment with the alkalis of the hardened cement paste (Na+, K+) to react. Thus it comes to driver seeming and/or to a Volumenzunahme with tears and flakings, which can damage the concrete construction unit strongly. When alkali-sensitively apply rocks, which contain amorphous or fine-crystalline silicates, like e.g. opal and stone and porous Flint. In particular the opal and stones occurring in Northern Germany in larger quantities as well as the Grauwackevorkommen in the Lausitz can contain harmful quantities of silicic acid soluble in alkali. By use of cements with low effective alkali content (cement identification letter: WELL) and by delimitation of the cement content in the concrete, the alkali reaction can be usually avoided when using concrete impacts with alkali-sensitive components. Large data in addition are to be found in a guideline of the German committee for reinforced concrete.

Due to damage from alkali reaction among other things the 1965/66 delighted salmon military bridge in Luebeck had to be torn off two years later again and kilometers of prestressed concrete railway sleepers of the German National Railroad had to be exchanged.

Articles in category "Alkali silicic acid reaction"

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• A hydrated potassium layer silicate and its crystalline silicic acid A
  silicate K-SH and the derived crystalline silicic acid sug-. gests that these compounds are intracrystalline. reactive. layered silicates. The alkali/Si02 ...


• Crystallization of silica gel in alkaline solutions at 100 to 180 ...
  metal oxides, and alkali-metal salts on the crystallization ... reaction of the resulting silicic acid from ion exchange. with water:. H-(silicate) + H20.: ...


• Electron micrographic study of precipitates formed by interaction ...
  Association of alkaline phosphatase with silicic acid in precipitates formed in dilute solution was studied as a model for the nonspecific reaction between ...