CEMEX DSM have commenced work on the next phase of the North Yorkshire Polyhalite Tunnel project. The £3.2 billion project is constructing Woodsmith Mine – south of Whitby, North Yorkshire – to extract polyhalite, and a tunnel system to transport it to a materials handling facility and harbour at Teesside.

The polyhalite deposit is the world’s largest and highest-grade fertiliser of its type. This is one of the final sections of tunnel and the most complex to construct. We have supplied our Spray Concrete in Silo Solution to this project in the past and our versatile solution lends itself to complex, difficult to reach sites; with this final section involving tunnelling under the North Sea we were called upon again to innovate.

The requirements of the site are such that there are a number of specific challenges, the spraying is taking place under the North Sea 17km from the point of production at the site silo. The dry silo concrete is manufactured/mixed wet via the silo and mixer into an 8m3 rail configured torpedo mixer which takes 90 minutes to travel the distance along the tunnel to discharge into the concrete spraying pump.

Due to the time it takes to make the delivery it is necessary to have an extended open life; the additional hydration control admixture is added by liquid into the mixer via a calibrated pump, and to measure the amount of product being discharged into the torpedoes the silos are on load cells which are able to calculate the weight of the product made.