Hanson celebrate TwentyTwo contract milestone
Company half way through three-year concrete supply contract for City of London’s tallest building
HANSON have reached a key milestone in their contract to supply concrete to TwentyTwo, a £591 million, 278m high tower which is set to be the tallest building in the City of London on completion next year.
The company is half way through its three-year contract to supply concrete to the project – formerly known as The Pinnacle – and has delivered more than 52,000 cubic metres of structural concrete mixes for use in the core, columns and floor slabs.
All of the mixes contain Hanson’s Regen ggbs (ground granulated blast-furnace slag) cement replacement product, which enhances the durability of the concrete while adding to its sustainability credentials.
Regen is manufactured from a by-product of the iron-making industry and using it to replace 1 tonne of Portland cement reduces the embodied CO2 of the concrete by around 850kg. Its use in the raft slab – which contains 68% Regen – also helped minimize the production of heat, reducing the risk of thermal cracking.
TwentyTwo, located in Bishopsgate, will offer 62 floors of flexible workspace for up to 12,000 people. The steel-framed tower has a central supporting jump-form concrete core and perimeter concrete columns.
Hanson are supplying a range of bespoke mixes to contractor Careys Civil Engineering from their Kings Cross, Silvertown and Victoria Deepwater plants. These include jump-form and lightweight concrete mixes as well as a complex design for 22 feature columns ranging in size from 4.5m to 16m high.
‘We have pumped the lightweight concrete mixes higher than ever before,’ said Ian Goddard, technical production manager at Hanson Concrete. ‘By supplying 54 floors for the project, so far, we have already exceeded the previous record in London, which was 50 floors at One Canada Square, Canary Wharf.’
Matt Kirsop at Careys Civil Engineering added: ‘Hanson have supplied concrete mixes that have been successfully pumped up to a height of 270m. The mixes are highly workable allowing our operatives to efficiently place and achieve the required finish.’