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Acids and concrete

Acids generally attack the surface of concrete by dissolving the matrix leading to surface disintegration.

Concrete is attacked by most acids. The table shows the rate of attack of various common acids. Acids may become more concentrated due to evaporation and this can lead to an increased rate of attack.

Rate of attack at ambient temperature Inorganic (mineral) acids Organic acids
Rapid Hydrochloric Acetic*
  Nitric Formic*
Moderate Phosphoric Lactic**
Slow Carbolic  
Negligible   Oxalic

* When concentrated, otherwise slow
** When concentrated, not as milk

Many acids are the products of reactions of other substances that may, in themselves, be harmless or may only be present in low concentrations in these substances. These are outlined in the section headed ‘Action of other substances’.

Acknowledgement: The Concrete Society

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TR54 Diagnosis of deterioration in concrete structures- identification of defects, evaluation an