Now that that concrete pouring has resumed onsite following the wet and cold weather, we thought we would give you an insight into how our construction team ensure the turbine foundations will be fit for purpose. Our site team take quality control extremely seriously. There are two concrete pours in each turbine foundation that can only happen once the correct preparations have taken place.
Preparing the foundation for concrete
The first job in this process is the preparation of the base foundation for the concrete pour. We do a final check of the steel reinforcement and then shuttering is put into place and used as a mould to ensure the correct dimensions are achieved. Screed rails are used for finishing to create an even surface.
Pumping the concrete
A long reaching pump is used to pump the concrete from the delivery lorries into the foundation – starting at the middle. The pump operators use a remote control during this process, which means that they can stand close to where the concrete is poured, making sure it is placed accurately and safely.
Quality control – slump test
Quality control is very important and we continually test, starting with a slump test upon delivery to check the workability of the concrete. The way it flows and the level of moisture must be within a determined range. We then take spot samples throughout the day as the concrete is poured to form test cubes. These are taken to a laboratory for destructive testing, so we can have complete confidence that the concrete in each and every foundation is of a consistently high quality.
The final section of concrete
The final stage is to pour the smaller pedestal upstand section (see picture at the top), with additional reinforcement and a bolt ring inserted at the top. A second set of prefabricated shutters are used to mould the final concrete pour. Both pours combined amount to 640 tonnes of concrete and the main pour alone takes 12 hours to complete. It really is a good job that the team have an onsite batching plant and don’t have too far to travel.
The turbine towers are bolted to this upstand, with only a very small section of the foundation visible when construction is complete. Once the concrete has cured (set), the previously excavated material will be backfilled and compacted in layers on top of the concrete to add further weight and stability to each base.