Description of One Coleman Street
One Coleman Street is a 180,000ft², ten-storey office development in a prime location along London Wall in the City of London. The office development incorporated a number of offsite pre-cast methods to speed construction, reduce waste on site and satisfy the requirements of the external façade geometry.
The building anticipated increased performance requirements under the Building Regulations, which were the stimulus to reduce glazing areas while enjoying external views from the building. This resulted in the striking external façade geometry that was realised using pre-cast concrete façade elements.
The main lift and stair cores used the twin wall pre-cast concrete core wall system to increase overall construction speeds. This was the first application of this system in the UK with composite steelwork floors.
The project was also the first major development in London to use recycled secondary aggregates in the main structural concrete. The project used the waste rock from china clay production, known as stent, for the course aggregate
Fly ash, a by-product from coal power stations, was used to replace cement in the concrete mix. The combination of stent and fly ash brought the overall recycled content of the main structural concrete to about 50% by mass or just over 70% by value.
Using 30-40% fly ash in place of Portland cement saved about 500 tonnes of CO2. Every cubic metre of this concrete saved one tonne of primary aggregate from being quarried and one tonne of waste from being tipped onto spoil heaps.
Using recycled content in concrete has been possible for some time. However, perceptions that it might not perform as well as traditional materials and that it might cost more have held it back.
By using recycled content effectively at One Coleman Street, Arup has established how these barriers can be broken down, and ‘waste’ material used on commercial projects. It has led to successful use of recyled content on other projects in London.