Supporting heavy footfall with lightweight concrete

Capital Concrete supply bespoke lightweight mix for heavily used pedestrian bridge in East London

BESPOKE concrete design incorporating an innovative lightweight aggregate has allowed Capital Concrete, part of the Brett Group, to meet the stringent weight specification on a project to upgrade a busy pedestrian bridge between Stratford International Station and the Westfield Shopping Centre in East London.

The original construction of the walkway was designed to support wooden decking and upgrading the surface to more durable concrete paving required a special lightweight concrete mix to create a thin base that would meet the structure’s weight restrictions. To achieve the required specification, Capital Concrete chose a lightweight aggregate for its low density and high crushing strength.

Jack Sindhu, technical manager at Capital Concrete, and his team worked closely with contractors Roland Construction Ltd to ensure the concrete mix was developed to meet the specifications and objectives of the project, trialling several mixes before selecting the optimum design.

‘We had to ensure the specifications of the lightweight fill concrete were met – specifically a density of 1,800kg per cu metre and strength of C20N per sq mm – because of the weight limitations on the bridge,’ explained Mr Sindhu.

As well as the C20 mix, a C40N per sq mm mix was also designed and supplied. Mr Sindhu continued: ‘Looking at alternative products gave us the opportunity to create new solutions to meet our customer’s often complex needs.’

Capital Concrete’s plant at Bow had to be prepared and ready to accept the lightweight aggregate, ensuring there were no issues with contamination. Concrete truckmixers were washed and the plant’s belts washed down prior to supply.

Owing to site restrictions and the low volumes of lightweight concrete required, it was decided not to pump the concrete. Instead, the concrete was discharged from the truckmixer to a site dumper which delivered it to the bridge deck.

Roland Koncius, managing director of Roland Construction Ltd, who carried out the works on the heavily used footbridge, commented: ‘It was good working with Capital Concrete and the project was completed successfully without delays.’