Lutz Petersen, manager of Transportbeton Bremerhaven-Osnabrück GmbH & Co.KG reports: “We have contractually guaranteed a maximum hourly output of 80 cubic meters for the tunnel. To fulfil our commitment, we have expanded our capacity through the addition of a mobile production facility. We are therefore well positioned to supply the construction site with structural and diaphragm wall concrete, as well as to deliver to our other customers as usual.”
The near-surface two-lane tunnel will be built using the cut-and-cover construction method. The water pressure resistant diaphragm walls have a depth of up to 32 m, and the 9 m long wall panels will be filled with concrete from the bottom using the tremie method, where the end of the pump hose remains permanently immersed below the surface of the concrete.
Cemex developed a special admixture for the diaphragm wall concrete, in order to achieve a stable consistency with limited water content, ensuring the required quality. Additionally, the project required a fire-resistant concrete for the tunnel walls, which was created using polypropylene fibres, which were added to the fresh admixture via a special system. In the case of a fire, the fibres would melt, creating open spaces for water vapour to penetrate.
To ensure sufficient capacity during the delivery of the concrete of the tunnel walls and additional diaphragm walls, an additional mobile ready-mix concrete plant will be erected for the duration of the project, bringing the number of plants supplying the project to 3.
"The stationary high silo plant has a capacity of 80 cubic meters per hour, the new mobile row of concrete dosing units achieves an output of 60 cubic meters; added to this is the ready-mix concrete plant of our supply partner", explains Lutz Petersen. "This enables us to ensure continuous supply of all parallel construction stages."
