Brief
This project required the complicated supply of ten 120m³ ready-mixed concrete pours for the relining of water tunnel walls.
Solution
In order to reach the internal cylinder shutter in the tunnel with limited access, the ready-mixed concrete had to be poured over a great distance. Special ready-mixed concrete was designed by our technical department that would enable this to be achieved and with the material still being workable at the delivery end whilst maintaining the specification.
Special admixtures and cohesion aids enabled the concrete mix to remain workable for up to an hour after leaving the plant as well as preventing segregation under the huge pressures in the delivery pipes and pump. The logistics and timings involved had to be carefully calculated as once the pumping had commenced, the pour could not stop until the full amount had been delivered and set.
With such unique and complex projects, unforeseen issues can arise. The initial pour identified problems, causing the pumping to be delayed, which resulted in a backlog of fully loaded lorries waiting to deliver. Constant monitoring of the ready-mixed concrete together with addiional additives to prevent it setting in the drums was required until the pumping recommenced.
However this problem, coupled with a fuel shortage due to strikes in the area, did not hamper the project. Seventeen hours after the first lorry was loaded, the last truck made the final delivery. The project was completed successfully with total commitment.
