London Concrete has provided the dense concrete solution to support Crossrail track slab construction from Bond Street station through to Farringdon station. Businesses above the line along this section include recording studios, so noise and vibration are a particular concern.
London Concrete supplied ATC JV (Alstom, TSO and Costain), the contractors installing track on the project, with 4,000m3 of special heavyweight concrete track slab, constructed using MagnaDense, which is around twice as dense as normal aggregate. In total, three grades of heavyweight aggregate as well as normal sharp sand were used to achieve the required density. MagnaDense from LKAB Minerals is formed of black ferrimagnetic natural iron oxide (Magnetite) and is mined in Kiruna and Malmberget in northern Sweden.
The technical team at London Concrete helped ATC with the design and development of the mix design and dedicated 12 months to an extensive trial process. This work was broken down into laboratory and plant trials culminating in a full pumpability trial of the final mix design before any concrete was supplied to the site.
Due to the complexity of the concrete mix and its components, London Concrete set up a dedicated plant at Battersea for the contract. As a result of trials, pulverised fuel ash (PFA) was added to the mix to improve pumpability and help meet the durability requirements of the specification.
London Concrete managing director Luke Smith said an innovative approach was required to pump concrete more than a kilometre horizontally. “Overall it was a particularly complex job with no margin for error,” he said.
London Concrete started work on the project this summer and is scheduled to finish in 2017.