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Sulfate in concrete

Excessive amounts of mobile sulfate, derived from aggregates or other constituents in concrete, can cause disruption due to expansion. BS 8110 part 1 Structural use of concrete, 1985, had a limit of 4% by mass of cement based on the total acid soluble sulfate method expressed as SO₃ (clauses 6.2.5.3). This restriction was dropped in the 1997 edition as materials were deferred to BS 5328 Concrete (now withdrawn) where it stated that the limits were meaningless to apply. The current Standard for specifying concrete, BS 8500 Concrete does not have a limit to the sulfate content in concrete. If there were a limit many lightweight and blastfurnace slag aggregates, with long histories of satisfactory use, may be excluded.

However, specifications for many constituent materials (aggregates, cement etc) place limits on the sulfate content. Also, in the UK, sulfate problems caused by naturally occurring aggregates are rare. Where an new source or material is to be considered or is suspected of containing sulfate, it should be assessed before being used.

Note, some Standards quote Sulfate as SO₄. The conversion of sulfate: SO₄ x 0.833 = SO₃

There is a limit for sulfate (SO₄) in BS EN 1008 Mixing water for concrete of 2000mg/l, as tested in accordance with BS EN 196-2

Acknowledgement: Concrete Society

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TR32 Analysis of hardened concrete - 2nd Edition