CEMEX sprayed concrete for London's 'Super Sewer'

More than 40,000 tonnes of primary sprayed concrete being supplied for biggest sewage project in UK

CEMEX are providing more than 40,000 tonnes of a complicated lining spray concrete for the construction of the Thames Tideway Tunnel, the biggest infrastructure project ever undertaken by the UK water industry.

The tunnel is being built to upgrade the London sewer system’s ability to cope with the city’s growing population. Currently, London relies on a 150-year-old sewer system built for a population less than half its current size. As a result, during periods of heavy rain, the current infrastructure can become overwhelmed.

The new 25km tunnel will intercept, store and transfer sewage waste away from the river Thames. Starting in Acton, in west London, the Thames Tideway Tunnel will travel through the heart of London at depths of between 30m and 60m, using gravity to transfer waste eastwards, to be processed and dealt with in a modern state-of-the-art facility.

CEMEX’s primary lining spray concrete is being used for the shafts and launch tunnels in the central part of the project – a 12.5km stretch of the tunnel under central London which is being constructed by FLO – a joint venture between Ferrovial Construction and Laing O’Rourke.

The concrete is sprayed from bottom to top in one continuous operation until the shaft wall is complete. An extremely complicated mix is required, consisting of eight separate constituents which, when combined, give an ultra-high strength of +60N per square millimetre, a consistency of 600mm flow and a workability retention of two hours.

When sprayed it has to adhere to the tunnel or shaft wall/ceiling and gain strength immediately at a very rapid rate. The concrete also needs to be highly pumpable, in some cases with a pipeline length of up to 400m.

CEMEX manufacture the product at their dedicated spray concrete plant in Buxton, from where it is transported to central London at rates that peak at around 3,000 tonnes per month. Supply is likely to continue for several months, although this may need to be extended due to the impact of the coronavirus pandemic.

Sergio Menendez, president of CEMEX Europe, Middle East, Africa & Asia, said: ‘The Tideway project is one of incredible scale which will solve serious capacity issues with London’s sewer system and have considerable benefits for the area’s wildlife and population, while also creating jobs, a rejuvenated river economy and new areas of public space.

‘This is a serious piece of engineering and we’re proud to be working with world-class contractors to build this key infrastructure in the most sustainable and cost-effective way possible for one of the world’s greatest cities.’

Michael May, sales manager for CEMEX Mortars Europe, added: ‘Our sprayed concrete forms a key part of the central part of the tunnel and it was vital to get the complicated mix right. Fortunately, we have worked with FLO before and so there was already an understanding of the works required and the performance required from the material to be supplied.’

Borja Trashorras, project manager at FLO’s Albert Embankment site, said: ‘CEMEX’s primary lining spray concrete provided a good solution at Albert Embankment foreshore for the construction of both connection tunnels and our 53m drop shaft through some challenging ground conditions.

‘Having sprayed over 5,000 tonnes for this package of works meant we built a strong and reliable line of communication with CEMEX. Logistical planning was essential in the delivery of these works due to our central London location, which CEMEX were able to co-ordinate and support with ease.’