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Ready mixed concrete cuts time and effort on Tube upgrades


'JUST ADD water' concrete is cutting through the inconvenience of mixing separate ingredients on conned construction sites, according to concrete supplier Lafarge.

The combination of restricted access, oppressive conditions and limited hours make construction work on London's Tube network a tough job. But the constraints are driving forward innovations to make sure the work gets done quickly, easily and with quality assurance.

This is why station upgrade work on the Northern and Piccadilly lines has used Lafarge Cement's new ready-to-use Blue Circle concrete.

Lafarge has created a preprepared concrete mix, similar to a giant, 25kg bag of PostFix. The thinking behind it has been described as: 'Why bother spending the time and effort putting all the ingredients together when it can come lumped together in one sachet?' Blue Circle's sachets contain speci portions of Portland cement, sand and aggregate, and just need water added to make up the perfect serving.

The concrete comes in three grades: coarse, fine and multipurpose. The C32/40 coarse concrete contains aggregate up to 20.5mm diameter, while the C32/40 fine concrete contains aggregate up to 10mm diameter.

Both are suitable for use as a structural concrete while the multi-purpose variety is used for general maintenance jobs such as xing posts.

More than 20,000 bags of coarse C32/40 concrete have so far been used to resurface platforms on Piccadilly and Northern line stations.

Contractor Scanmoor is currently carrying out the work. Its site person in charge Vince McGirr describes how the ready-to-use concrete has bene ed commuters and contractors alike. 'One of the biggest challenges for the station upgrade work is the need to keep the stations open as much as possible. In a few cases we have had to shut the platforms - but that causes problems for the Underground and for commuters.' Using the sachets has meant that less space is needed to store the concrete compared to that needed for ready mix equipment.

Lafarge Cement UK senior technical advisor Ian Heritage added that the new Blue Circle concrete has also been used on secluded coastal sites on the west of Scotland, where only small quantities of material could be carried down to the quayside, and the contractor wanted a guaranteed concrete strength to minimise wastage.

'The product appeals to people who are looking for concrete of a particular strength and who don't want the bother of having to carry out crushed concrete cubes strength checks, ' he said.

'If you add the right quantity of water, you'll have a guaranteed minimum strength concrete - of course it will be cheaper to mix it on site - but what you're buying is a consistent, factory produced batch'.

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