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Causes of Damage to Concrete-sulfate deterioration

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Sodium magnesium and calcium sulfates are salts that can react with hardened concrete and cause deterioration for concrete structures. Sodium magnesium and calcium sulfates react with hydrated lime and hydrated aluminate in cement. This reaction will produce calcium sulfate and calcium sulfoaluminate. The volume of these products is greater than the volume of the cement paste, which undergoes the reaction with sulfates salts. This reaction will cause a destructive volume change. The increase of existing concrete will generate stress, which may result in concrete cracking and spalling. The using of sulfate resistance cement is recommended where the sulfate concentration is high. Sulfate resistance cement or cement type V will resist the sulfate reaction. Type V cement has a low calcium aluminate content, which enables this cement type to provide a good resist the sulfate deterioration. Therefore it should be specified and used when it is recognized that concrete must be exposed to soil and groundwater sulfates.

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Sulfate deterioration can be delayed for concrete that is undergoing active sulfate deterioration. The delaying of concrete deterioration can be done by the applying of thin polymer concrete overlay or using of sealing compound to seal the surface of concrete and reduce the permeability which can helps in reducing the ingress of sulfate to concrete and reduce the sulfate reaction with cement, interpreting of cyclic wetting and drying will help in slowing the reaction and reducing the sulfate deterioration. Removing the source of sulfate, such as removing the waterborne sulfates, will help if it the primary source of the sulfate reaction. If the sulfate deterioration cant is stopped or slowed, the concrete shall be removed and replaced with concrete made from cement V type. The using of cement V type will ensure excellent resistance to sulfate deterioration.

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