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Professor Les Clark

Chairman - Thaumasite Expert Group

The six month deadline given to the expert group set up by construction minister Nick Raynsford to investigate thaumasite sulphate attack on concrete is a tight one.

But chairman Professor Les Clark has a very good incentive to complete the work on time.

'On 1 October I take over as president of the Institution of Structural Engineers, which will be virtually a full time job,' he explains.

Some may consider Clark an unusual choice to head up the group: he is a structural engineer rather than a materials scientist, and has never carried out any research into thaumasite. But having sat on the Alkali Silica Reaction Committee he has earned a strong reputation within the concrete industry.

The right man for the job, seems to be the view from the industry - someone who approaches problems not just from the materials but also from the structures point of view.

Clark has been professor of structural engineering at Birmingham University for seven years, and is well known for his work on the committees of the Institution of Civil Engineers, the American Concrete Institute and the Concrete Society to name but a few.

He finds the prospect of investigating another problem at the 'materials/ structures interface' challenging but fascinating - and regards his appointment as an honour. He also claims not to be phased by the relatively little research that has been carried out into the phenomenon to date.

'What appeals about engineering is that you are generally dealing with inadequate data - that to me gives it a certain amount of magic,' he says.

Clark has yet to visit the M5's damaged structures and has not been fully briefed on the Building Research Establishment's findings. Until he has seen all the facts, he says, he is not prepared to speculate on how widespread attacks might be.

But he is keen to allay fears, and cites the past hype surrounding the alkali silica reaction (so-called concrete cancer) as a way of putting the problem into context.

'ASR was not as big a problem as many people would lead you to believe. It is a serious problem in terms of appearance but not in terms of structural performance,' he says.

The structure and role of the expert group are also yet to be finalised. But Clark says it will represent 'everybody with an interest' in structural concrete.

'There are obviously a lot of different interests involved but we will be trying to get a balance between scientific input and the pragmatism required to give practical advice,' he adds.

Matthew Jones

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