Crossrail using 3D-printed concrete to build its stations (Ian Visits)

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When you start to use the new Elizabeth line stations next year, among its many achievements will be the first large scale use of 3D-printing in concrete.

The use of 3D printing has made possible one of the more distinctive features of the future Elizabeth line stations — the curved concrete panels that will line the inside of the passenger tunnels and some stations, and sinuously glide around corners in a way never seen before in a tube station.

Although it has been technically possible to use concrete as a material in 3D printing for a few years, the objects made tend to be small as larger panels of the size needed for Crossrail still have structural weaknesses in the design caused by the weak bonds between each layer as they are built-up by the 3D-printer.

What the Crossrail contractor fitting out the stations did was take a very different approach, they printed the moulds instead of the concrete. Building moulds to form concrete is a well known technique, but it’s very time consuming and wasteful. The traditional method is to carve the shape out of a solid block, then cover the rough surface with a tooling paste to create a smooth surface.

Not only wasteful in throwing away material that’s not needed, the tooling paste takes, on average, 12 hours to set. Each traditional mould would take around 16 hours to make, and that’s before you’ve even started with the concrete.

For a project as large as Crossrail, which needs around 36,000 concrete panels, this was far too slow, too expensive, and too risky in terms of things going wrong. An alternative was needed, and 3D-printing came to the rescue.

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Written by Long Branch Mike