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FLOOD DEFENCES

Limestone filler cement warning for Hexham Flood Defence

I refer to the article published in the August issue of NCE describing the use of limestone filler cement on the Hexham Flood Defence Scheme.

In 1988 I was a member of the BSI CAB 4 committee, which was responsible for drafting the British Standard for Concrete Mixes. I raised the problem of thaumasite in concrete containing limestone.

When concrete is made with limestone filler cements, it is more vulnerable to sulphate attack at low temperatures.

I understand that thaumasite has been found in some of the bridges on the M5. The limestone provides one of the ingredients of thaumasite, which can lead to a self-destruct mechanism of the concrete.

Certainly, limestone filler cements should not be used in concrete exposed to sulphates.

Derek Stewart Smith (M), derek.stewartsmith2@btopenworld.com

The Editor, New Civil Engineer,
​4th Floor, Harmsworth House, 13-15 Bouverie Street, London EC4Y 8DP
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