Sika concrete admixtures played their part in underwater repairs to foundations and stone piers for a major viaduct on the West Coast mainline in Carlisle. Spanning the River Eden between the Sheepmount area of Carlisle and Etterby, the 70 metre long rail viaduct comprises five stone piers and a concrete deck.

To repair the stone piers, Story Contracting installed a total of 64 tonnes of permanent interlocking sheet piles around the piers. The piles were driven to refusal, toeing into the mudstone bedrock.

Following this, 282m3 of Hanson concrete containing Sika® UCS Pak, a specialist underwater admixture, was poured between the pier and the sheet piles, with a capping beam formed at cut-off level.

Used for the production of underwater concrete and meeting the requirements of BS 8443, Sika® UCS Pak prevents the wash out of the cement paste and increases the cohesion of the concrete. Sika® UCS Pak is packaged in water soluble bags to enable ease of addition on site.

Andrew Stephenson, District Sales Manager at Hanson Concrete commented: “We worked with Story Contracting on a specialised concrete solution which would allow them to place concrete underwater without contaminating the river. A mix containing Sika® UCS Pak met these requirements and ensured the critical path of these foundations was a success.”