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Action on concrete corrosion

EXPERTS have issued new guidance on construction for contractors and designers following the publication of a report into concrete corrosion.

The report, released by the government and the Building Research Establishment, follows the discovery of thaumasite sulphate attack in the foundations of 14 bridges in the West Country. But up to 100 structures in the area could be subject to corrosion.

Construction minister Nick Raynsford last year appointed Professor Leslie Clark, president of the Institution of Civil Engineers, to study the thaumasite form of sulphate attack on concrete. The move followed the discovery of deterioration in some of the concrete columns in bridge structures over the M5 in Gloucestershire.

This week the professor's group concluded that the thaumasite form of attack will only occur in buried Portland cement-based concretes when all of four primary risk factors are present. These are:

the presence of sulphates or sulphides in the ground;

the presence of mobile groundwater;

the presence of carbonate, generally in concrete aggregates;

low temperatures.

Mr Raynsford said: 'The Highways Agency is reviewing its interim guidance on thaumasite and will be issuing updated guidance shortly.'