Exploding concrete banned

Contractors are banning foam concrete on civils sites after two explosions left construction workers with fractured feet.

The blasts were linked to the use of incinerator bottom ash (IBA) in foam concrete.

At least two contractors - Barhale and Enterprise - have banned foam concrete containing IBA from all their sites, with others understood to be following suit.

The product is widely used in the industry - most commonly in utility trench filling and road construction.

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The worst explosion occurred at Mill Green, Hertfordshire where Barhale was decommissioning a pumping station for Thames Water (pictured). Two workers sustained fractures to the ankle and foot.

Foam concrete infill had been placed into a dry well, and extended beneath an existing metal floor overnight. Hydrogen produced by the foam concrete built up beneath the metal floor and exploded the next morning when the two workers were standing on it. The gas is thought to have been ignited by a spark from a grinder.

Andy Dodman, group health and safety manager at Barhale, told CJ: "Our investigation has concluded that the presence of aluminium particles in the IBA product generate hydrogen gas after the concrete mixing process. The use of foam concrete containing IBA is therefore no longer permitted by Barhale, only foam concrete mixes containing inert ingredients."

The other explosion occurred in Dudley, where Enterprise was carrying out roadworks for Severn Trent.

A spokeswoman for Enterprise said: "We did experience a small explosion on one of our water sites in June when we were using foam concrete mixed with IBA.

"After an extensive internal investigation we have now banned IBA in this process across all our water operations and in our supply chain.

"We have also made a recommendation to The Highway Authorities and Utilities Committee that it becomes a standard stipulation for anyone using foam concrete."

The Health & Safety Executive said it has launched an investigation into the two blasts.

Barhale's foam concrete supplier, All County Concrete, declined to comment. The firm was supplied with IBA by Ballast Phoenix.

Ballast Phoenix managing director David York said there was no reason for contractors to stop using the product. He said: "It's premature to say that IBA was the cause of these incidents. Foam concrete with IBA has been used for years, and as long as it is used correctly, in a well-ventilated area, it is a good, safe product."