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Visitors to Civils 98 will find a wealth of new developments on display. This week Cooper Clarke and Marshalls give us a preview of what to expect. Clearing the deck

Images of the Golden Valley interchange near Cheltenham are bound to feature prominently on Cooper Clarke's stand at Civils 98. More than 700m of the company's new Bridgdek 2 twin channel drainage system will be installed by main contractor Jarvis Construction during its £3.8M contract to strengthen and refurbish the three bridges which carry the A40 over the M5. This is the biggest order for Bridgdek 2 since it was first launched two years ago, although the system has been installed on 30 smaller bridges already.

Cooper Clarke finance director Cliff Maylor says he expects interest from more than just the UK bridge engineers who will be attending the show. 'Bridgdek has already attracted so much international attention we've just produced a video about the system in 20 languages.' The reason, he says, is 'because the problems it solves are not confined to the UK alone'.

These problems began when bridge deck membranes became much more efficient, Maylor says. As a result, more and more contaminated rainwater is trapped in the base course. When a vehicle crosses the bridge its wheel loads forces 'bow-waves' up through the wearing course, washing away fine particles within the asphalt matrix.

This erosion seriously reduces the life span of the surfacing. The same bow-wave build-up of hydrostatic pressure within the base course can also break down deck waterproofing and movement joints, Cooper Clarke claims.

Bridgdek 2 solves this problem by providing separate continuous drainage for both normal surface rainwater run-off and the base course itself. With this set-up the bow-waves actually pump the trapped water out into the drainage system, in a series of pulses that helps to flush any silt out of the system.

'It took us six months to develop the original idea,' says Maylor. 'Most of this time was spent getting the composite top section right, and on testing.'

This top section, which sits on a ductile iron channel section, is available in a wide range of colours. Tests insitu showed that almost 20% of the water entering the system came from the base course - a proportion that increases with the age of the surfacing, Maylor reports.

The system also includes components to allow it to cross expansion joints. Maylor says that 'nine out of ten' bridge engineers respond very positively to the concept. But Cooper Clarke was not ready to rest on

its laurels. It saw the possibility of amending the basic Bridgdek 2 system to make it compatible with porous asphalt, a wearing course option normally unavailable to bridge engineers.

Adding extra drainage slots to the cast iron channel units above the level of the secondary base course drainage channel created Bridgdek 3. These new slots align with the wearing course, allowing the water that drains into the porous asphalt to pass into the main drainage channel along with any surface water.

Maylor estimates the global market for this type of drainage system is around £10M annually, and the Bridgdek concept is protected by European and US patents. But Civils 98 will give Cooper Clarke the opportunity to display other products on its stand as well.

The company plans to show its Geofin and Geoflex methane gas protection systems, and its access ducting equipment for street lighting and traffic signals.

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