In April Firth coordinated and supplied approximately 850m3 of concrete in one night for the base of five new transformers for Transpower's substation at Bunnythorpe.
Due to the huge volume of concrete required in one night, concrete supply was planned and coordinated precisely to ensure an uninterrupted flow during the mass pour, and to ensure that the duration of the pour was within the limitations of the concrete placers allocated to the project. Average round trips, load sizes and rest time for drivers were all factors that were considered when coordinating this massive pour. There were also the technical requirements of the mixes to be considered.
"The dimensions for the base for these transformers are 46m(L) x 14m(W) x 1.3m(D)," said Alistair Bennett, National Technical/Materials Engineer for Firth. "Due to the 1.3m depth we had to cater for the heat of hydration generated inside the transformer base. We used specialised software to model the rate of heat generation and loss in the base and monitored the temperatures in real time through a cross section of the base using cast-in probes."
With 14 trucks in total from the area, including four on loan from Firth Wellington, work began at midnight. After 13 hours and 850m3 of concrete, the base was completed.
"It was a long night but we finished just after midday the following day," said Graham Hickling, Project Manager from Armstrong Downes Ltd. "Firth had a good system and the guys from Manawatu Pumping did a good job keeping up with the supply. It was a very big pour but it was coordinated very well. On Firth's recommendation we also had polystyrene insulation on the formwork and they used probes throughout the base to ensure there wasn't a heat problem. Firth is our concrete supplier for the region and we have a very good working relationship with them. The job went very well and all parties where very happy with the final result."
