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Crossrail is one of the iconic UK infrastructure projects of recent years. However, given the unprecedented level of belowground engineering involved, coupled with the vast area of central London the line would be servicing, ensuring any activity did not adversely affect any above ground infrastructure was a key challenge faced by Crossrail contractors BBMV (Balfour Beatty Morgan Vinci).

Division(s)
Europe Materials
Business Type(s)
Readymixed Concrete
Location
London, United Kingdom

The challenge

With so many work sites and concurrent activities, maintaining the project schedule was another big challenge, requiring reliable and solution-oriented partners.

Tarmac has worked extensively on the project – including at key locations such as Bond Street, Finsbury, Whitechapel and Paddington stations – providing specialist and bespoke solutions tailored to the exacting performance characteristics demanded by Crossrail.

The solution

Many of the buildings located above or near to the Crossrail route were fitted with movement sensors, which detect even the smallest of movements caused by belowground engineering works. Compensation grout is then applied to corresponding injection points if any movement is detected. However, due to the sheer scale and depth of the construction, the original specification compensation grout used in the Bond Street, Whitechapel and Finsbury areas struggled to keep up with the requirements. To rectify the situation, and ensure the Crossrail project could continue unhindered, BBMV turned to Tarmac’s Pozament team. They created a bespoke formula of compensation grout which, when pumped from the surface to the substrate, remains live in the lines for over 45 minutes, only gelling and setting once it passed beyond the injection point.

Throughout the project’s duration to date, Tarmac’s Pozament team has supplied over 4,000 tonnes of low-strength, high-purity grout, which was deployed through 1,800 individual injection points.

Another value-engineered Tarmac product, TopFlow – a self-compacting mix containing ground granulated blast furnace slag – has also been widely used on the Crossrail project, including a significant portion of the 125,000 m3 of concrete used by Costain Skanska JV for pilling, D-walls and structures at the Bond Street Station. Using this bespoke concrete allowed them to reduce costs and shorten project timescales.

Due to the success of their collaboration on Crossrail, Tarmac and Costain joined forces again to apply TopFlow on the London Bridge project, where a bespoke self-compacting concrete was required for the 21 concrete columns and crossheads that hold the bridge decks above and allow for a spacious open concourse below.

Tarmac also successfully completed the longest continuous pour on the Crossrail project, supplying one load of concrete to the slipform paver every hour for a two-week period.

The outcome

When the construction of Crossrail is complete it will be the first entirely new underground line in more than 30 years. Tarmac is extremely proud to have helped deliver this ambitious scheme, one of the largest in the rail sector for many years.

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