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Largest continuous underwater concrete pour takes place in Scotland

World Cement,

Professional Concrete Pumping (formerly Pochins) has been highly praised for its role in the concrete pour for the Forth Replacement Crossing South Tower in Scotland, believed to be the largest continuous underwater concrete pour in the world.

The record-breaking pour, also believed to be the third largest concrete pour of any type, took more than 15 days to complete. A total 16 869 m3 of concrete was poured in 364 hours.

Praising Professional Concrete Pumping's role in the ambitious project, Christian Niemietz, Head of the Forth Crossing Bridge Constructors (FCBC) Caisson Operation, said: “The South Tower continuous concrete pour was a significant logistical challenge. Everything went extremely well and Professional Concrete Pumping did an excellent job.”

The concrete was transported to the South Tower caisson by four barges dispatched from the FCBC's batching plant in nearby Rosyth Docks. The barges made 273 individual journeys to and from the site, negotiating a busy waterway (the Firth of Forth) and covering a total distance of 1800 km – the approximate distance from John o'Groats to Land's End.

Professional Concrete Pumping Forth Road Team. (Photos courtesy of Forth Crossing Bridge Constructors).

The success of the project depended upon there not being the slightest interruption in the pour and an impeccable performance from the six shore-based Professional Concrete Pumping concrete pumps was therefore critical.

The operation involved the creation of huge concrete plugs inside the foundation caissons and Central Tower cofferdam. It was launched in late July 2013 with 7400 m3 being successfully poured into the North Tower caisson. This was followed, in early August, by a 4400 m3 concrete pour into the Centre Tower cofferdam. Finally, in late August, came the world-record-breaking South Tower caisson operation with a total of 16 869 m3 of concrete poured into the caisson to form a solid plug more than 26 m in depth. The pour was completed on 5 September.

The average pour rate for the South Tower caisson was 47 m3 per hour, with the total weight of the concrete almost 39 000 t, the equivalent of 3250 London buses.

Carlo Germani, FCBC Project Director, said: “The underwater concrete pour operation has gone without a hitch thanks to extremely detailed advance preparation carried out by the team. This achievement is a credit to the skills of everyone involved. It is a huge milestone for the project because it means that the focus can now switch from below the waves to the upward construction of the three towers above the waters of the Forth.”

Construction on the Forth Replacement Crossing commenced in the summer of 2011, due to the deterioration in condition of the neighbouring Forth Road bridge, which opened in 1964, and concerns over its long-term viability. The new three-tower 2.7 km (1.6 m) cable-stayed bridge is due to be opened to traffic by the end of 2016.

The new bridge's towers will be 207 m above high tide, 25% higher than the current Forth Road Bridge. A total of 30 000 t of steel and 150 000 m3 of concrete will be used to construct the new bridge, which will support a two-lane motorway with hard shoulder and include modern wind shielding to protect traffic from the effects of wind buffeting.

Adapted from press release by

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