To overcome the problem of traditional underground stations, which tend to be illuminated by artificial lighting and can often be quite cramped and unpleasant to be in, the new station has an opening of around 440 m2 in the roof of the tunnel. The result of this feature is that passengers arriving or departing from the station now have the distinct sensation of being in an underground station but, thanks to the direct connection that has been created between the inside and the outside of the station, the underground tracks now receive natural air and ventilation.
SUPER ADMIXTURES AND CONSTANT SUPPORT
During both the regeneration phase and the waterproofing work on the underground tunnel, and then during construction of the entire station complex, Mapei worked in collaboration with the La Calcestruzzidue Srl concrete plant in Matera to develop the correct mix design for the concrete by providing all the technical support required.
The constant presence of the Mapei Mobile Laboratory during the various phases to manufacture and pour the concrete enabled the team to optimise work schedules and to make the most of all the potential of the Mapei admixtures.
Going into detail, around 1,000 m3 of SCC C40/45 concrete with 700 mm slump flow containing DYNAMON SR 914 acrylic super-plasticiser was used as a foundation bed to position the crossties and tracks inside the existing tunnel, an area which would have been difficult to reach using other systems.
The concrete was pumped without any particular problem along around 600 m of fixed hoses. The hoses were gradually taken apart and their overall length was reduced as the pumped concrete worked its way closer to the fixed pumping station.
The surface of the concrete was then thoroughly cleaned to remove any residual material that had remained after pumping. The steel spacers and gravel clusters were removed from the surface of the concrete.
MAPEGROUT 430 fine-grained, fibre-reinforced, normal-setting thixotropic levelling mortar was used to level off the surface of the concrete substrates.
The second pours of concrete for the tunnel between the floor slab and the walls were sealed with IDROSTOP B25, a special 20x25 mm hydro-expanding jointing tape made from a mixture of natural sodium bentonite and polymers.
The second pours on the walls and the gaps around the pipework passing through the concrete were sealed by applying MAPEPROOF SWELL, a one-component, hydro-expansive paste used to form flexible, waterproof seals.
In certain cases, such as when water started to seep through some structural elements, the flow was blocked off with LAMPOSILEX ultra-fast setting and curing hydraulic binder. Once the surfaces had been properly repaired, they were cleaned down and a coat of PRIMER 3296 acrylic primer in water dispersion was applied, following roller application of MAPELASTIC FOUNDATION, a two-component, flexible cementitious mortar, which is especially suitable for waterproofing concrete surfaces subject to both positive and negative water pressure.