The longest continual slipform pour in the UK has been carried out by Cemex UK on one of the five shafts for Thames Water’s £635M Lee Tunnel project.
Engineers from contractor, MVB, a joint venture partnership between Morgan Sindall, Vinci Construction Grands Projets and Bachy Soletanche, spent 29 days continuously pouring concrete into the slipform shutter of the shaft on behalf of client Thames Water.
Three cranes were used to deliver the concrete to three skips to pour into the 80m deep shaft demanding a total of 11,000m3 of concrete to the scheme. The concrete was batched onsite and placed at a rate that allowed the shuttering to rise between 100mm and 150mm per hour.
A bespoke C50/60 concrete was designed using a number of admixture blends to control setting times including Isoflex superplasticiser, MR 800D retarder. The concrete also contained 500t of steel fibres as reinforcement.
“This was a tremendous achievement with nine concrete mixes of different levels of retardation supplied on a regular and continuous basis to form an integral part of this vital structure. The materials have been developed using the latest technology and challenge our expertise, to ensure that we can meet the structural requirements of the tunnel. Such developments are key to helping to build a greater Britain,” said Chris Leese, Vice President, Readymix and Mortars.
The Lee Tunnel is first of two tunnels which will capture an average of 39 million tonnes of London’s sewage and by itself prevent more than 16 million tonnes of sewage mixed with rainwater overflowing into the River Lee each year.