CARBON FIBRE reinforcement is being used to strengthen defective floor slabs in what is set to become the world's tallest building, the Burj Dubai, sources on the project said this week.
Carbon fibre is 'being used on floors throughout the height of the building', confirmed an engineer working on site.
Reports of cracking in some of the floor slabs have leaked from the Burj Dubai site although the client and designers this week insisted that there were 'no serious problems'.
However, another project source said that there had been significant deflections in floor slabs in the lower storeys of the tower.
In this case external steel reinforcement had to be added to bring them up to the required strength, he said.
Carbon fibre strips can be bonded to the concrete surface to provide external reinforcement. The material's high tensile strength helps to reduce cracking or defl ctions in the concrete.
Andy Davids, chief structural engineer for Hyder, the client's engineer, said there were 'no serious problems' with the structure.
He would not confirm that carbon fibre reinforcement was being used, but said that 'all sorts of leading edge technologies are deployed in a building of this size'.
The concrete structure is currently about 400m tall, and will be just over 600m tall when complete.
This will be topped with a steel superstructure taking its total height to over 750m.
NCE understands that the tower's reinforced concrete floors span 9m and cantilever 3m at the building's edge, but are of relatively shallow depth.
It is understood that client Emaar invited tenders for a £35,000 contract to supply carbon fi re fabric last year, which was won by the Swiss firm Sika.
Work to apply carbon fibre strips to under strength floor slabs is ongoing, an engineer on the project told NCE.
He said that carbon fibre strips are being applied to floor slabs to compensate for weaknesses.
Emaar assistant project director Greg Sang denied carbon fibre is being used 'anywhere'.
'There are no structural problems, ' he said.
Eric Tomich, associate partner at Skidmore Owings & Merrill, which is architect and structural engineer for the Burj Dubai, also denied any remedial work was being carried out.
Sructural expert Stuart Alexander, WSP group technical director, said: 'A bit of cracking in a concrete floor slab usually isn't terribly significant. Most of the time you wouldn't need to fill them.' But he added: 'Things have to be pretty bad before you start putting carbon fibre on.' WSP is not involved in the project Burj Dubai is being built by a joint venture of contractors Samsung, Besix and Arabtech.