Durability of FRP in construction
Source:未知Author:admin Addtime:2018-02-02 15:16 Click:
Although new applications are now beingdeveloped, FRP has been used for a long timein the construction industry, particularly forcladding. Mondial House was built on thebanks of the River Thames in London, in1974, to a futuristic design, almost entirelyclad with bright white FRP panels. This wasa very large modern building, reaching aheight of 46 m.
The main cladding panels had a flutedsurface and were 3 m high x 1.8 m wide,except for the panels on the eighth floor,which were 6.7 m high. The panels werereinforced with foam cores and top hatstiffeners. They were contact moulded usingScott Bader Crystic 356PA ‘Class O’ fireretardant polyester laminating resin andisophthalic polyester gel-coat 65PA for goodweathering resistance and durability.
Mondial House stood next to CannonStreet station in the centre of London’sfinancial district. It was designed to holdswitching equipment, repeater stations,mains power generation, operator centresand training facilities. In the mid-to-late1980s the old equipment was stripped outand Mondial was updated with new computercontrol equipment. Mondial closed as anoperational BT building in December 2004 and demolition took place in 2006 to enable
the site to be redeveloped. Samples of the 33-year-old FRP cladding have been retrieved and are being evaluated by the Network group for Composites in Construction toassess their durability during this prolongedperiod in the London climate.
From a distance the panels still lookedbright white and in remarkably good condition.
On closer inspection they were foundto be dull and dirty, but certainly still veryserviceable and it is considered that theycould have remained in service for many more years. A section of one panel wascleaned and polished (quickly and easily by hand), which restored the colour and gloss to as-new condition with very little effort – very impressive considering the FRP had probably never been maintained in 33 years.
It is expected that FRPs will easily lastthe normal 50-60 year design lifetime of a building, and they are now being used for bridges with design lives of 120 years. Whilst conventional polyester gel-coats are clearlydurable for prolonged periods, they do tend to show surface dirt, particularly on plain coloured flat surfaces. They will also lose their initial gloss and darker colours will suffer fading over prolonged periods of UV exposure. The initial high-gloss appearance can be maintained with periodic cleaning and polishing but this is unlikely to happen for most building applications. The resistance to such degradation can be improved by incorporating surface textures and/or
intentional variations in the surface colour,both of which can make surface dirt retention less noticeable. It is also possible to incorporate other materials into the surface coating, such as natural stone, in granule or powder form, which can lead to a more natural ageing and weathering, which may be Mondial House FRP panel: half as removed from building after 33 years service; the other half cleaned and polished. more acceptable for some applications.
