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Clients in denial as concrete decay stalks Dubai buildings

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CONCRETE BUILDINGS in Dubai are at risk of collapse because designers and clients are ignoring research on concrete durability, materials experts have warned.

'Rapid concrete deterioration is a significant problem across the Gulf region, but is particularly acute in Dubai, ' warned Concrete Society director David Ball.

Ball is also founder and chairman of concrete additives rm David Ball Group.

'Relatively recent structures are showing signs of disastrous deterioration. I have seen buildings in need of repair before they're even open.' Ball said that clients and designers in Dubai are 'in absolute denial' of the problem.

'They won't acknowledge that they need to design-in protection, and are creating a nightmare for themselves.' Extreme environmental conditions with high temperatures and humidity, sulphates and chlorides make concrete attack more likely in Dubai. The Emirate has an exposure class of 12, which compares to a maximum class six in the UK's most aggressive environments ? for marine or sewerage structures, for example.

NCEI's sister magazine New Civil Engineer first reported on the challenge of building durable concrete structures in the Gulf region 32 years ago.

'Reactive minerals, the climate and water combine to produce a tally of crumbling buildings that grows longer by the week, ' NCE wrote then. Today, the situation is little changed despite extensive research into the performance of concrete in the region.

Sheffield University emeritus professor of mechanical engineering Narayam Swamy supervised a major research project in Dubai, completed in 1998.

Research by local universities in Dubai is ongoing.

'Normally concrete should give 50 to 60 years but in the Middle East deterioration becomes apparent after five to 10, ' said Swamy.

He warned that concrete subjected to Dubai's blistering heat and humidity falls prey to 'micro-cracking' that is invisible to the naked eye.

'Sudden changes in temperature, and high humidity result in thermal fatigue, which produces internal micro-cracking.

That occurs within seven to 10 days of curing, ' said Swamy.

Cracking reduces the compressive strength of the concrete and allows the ingress of chloride ions which attack reinforcing steel.

'Unless you monitor the structure very carefully you won't be able to detect deterioration until it's quite advanced, leading to problems with overall structural stability, ' Swamy explained.

He said that his research had led to a recommendation that surface protection be applied to all concrete structures to prevent chloride ingress. But, he added, 'as far as I know there's been no widespread use of surface coating at all'.

Ball said that prestige projects are generally protected, but that these account for only a tiny proportion of the structures being built.

Deterioration is compounded by the high water table adds Ball 'There's a very high water table 1m below the surface, and the water is brackish.

Constant evaporation is going on through the concrete superstructure. If your concrete is permeable, salt water will be drawn up from the ground, ' he said.

'Conditions are incredibly corrosive. A friend in Dubai recently took cores from buildings that were only around five years old.

'He found black holes where the reinforcing steel used to be, ' he added.

'Ferric oxide has a volume 10 times greater than steel. That creates expansive forces within the concrete, ' exacerbating cracking, said Ball.

'The structures remain OK under compression, but the slightest tremor, and they'll be down.'

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