Hinkley T-Pylons, UK

THE PROJECT

The design of electricity pylons remained the same for nearly a century until National Grid’s T-pylon project. Starting in 2021, 116 new T-pylons installed over four years along a 57km route across Somerset will connect low carbon energy from Hinkley Point C Nuclear power station to six million UK homes and businesses. Each pylon is 35 metres high, a third shorter than traditional lattice pylons, and have a smaller footprint on the land for to mitigate environmental impact. The pylons have a single column bolted to a mass concrete foundation, subject to significant wind loadings in service. The pylon bases required an ultra-high-performance grout specifically designed to cope with the effects of powerful cyclic movement. Fosroc were contacted to specify and supply a suitable product due to their long-standing relationship with the contractor, high quality site support expertise, and tried and tested products.

THE SOLUTION

Fosroc specified Conbextra BB92 for the pylon bases, which had been successfully proven for use on wind turbines on previous projects. It’s designed for structural grouted connections for onshore wind turbine foundations and non-structural offshore foundation connections, as well as for segmental concrete wind towers, and is non-shrinking with high early strength, flexural strength and fatigue resistance. Even at low temperatures, BB92 enables a quick return to service and removal of temporary supports due to its high early strength build-up.

THE BENEFITS

During application of the Conbextra BB92 it was vital that there was no segregation or bleeding to prevent pump blockages and ensure the required performance characteristics were achieved. This saved Balvac a substantial amount of time with no compromise on quality. The additional support Fosroc provided during toolbox talks and training sessions on the use of specialised pumps to optimise grout flow was invaluable to the contractor. The grout was successfully used for both construction phases 1 and 2, during 2021 and 2022. Conbextra BB92’s inherent high performance will help maintain the integrity of the pylons for the required life expectancy. The Hinkley Connection project will be ready to connect to Hinkley Point C in 2024, with completion scheduled at the end of 2025. Chris Bennett, Acting President, National Grid Electricity Transmission said: “We are always looking for innovative new ways to mitigate the impact of our infrastructure on the natural environment and projects such as T-pylons are a great example.”