An underground ceramic application

It isn’t the longest in the world – that record is held by the Norwegian Laerdals Tunnelen with its 24.51 km
extension. Nor is it the oldest, since according to the Bibliotheca historica written by Sicilian historian Diodorus Siculus (90-27 BC), the Assyrian Babylonian queen Semiramis dug a tunnel more than 12 feet high and 15 feet wide under the Euphrates to connect two buildings around 2800 years ago. And it isn’t even the most legendary, like the Crypta Neapolitana (at the eastern end of which is a tomb said to be that of Virgil), with its length of 711 metres, dug at the end of the 1st Century BC from Pozzuoli to Naples, thus avoiding the tortuous path along the slopes of the Vomero of the Via Antiniana per colles. Nonetheless the Base Tunnel, located in the section between Badia Nuova and Aglio, is a work of symbolic value not just for the entire Variante di Valico deviation of the A1 (Milan-Naples) motorway, but also due to its use of an innovative cladding for the interior walls, which opens up a new application for ultra-thin ceramic porcelain panels.
The Variante di Valico covers 66.6 km of the Appenine section of the A1 and, with 50% routed through tunnels, provides a solution to a long-standing problem in the motorway connection between the north and south of Italy.
As part of this large project (at 4.1 billion euro, one of the most complex projects recently completed in Europe), the design and construction of the base tunnel, with its 8.7 km route extending through two separate tunnels (one in each direction), and sections of more than 180 metres in length, is an important example in terms of the solutions adopted, and has been called by the authoritative Sole24Ore newspaper « a project of unique global stature ».
In this context, particular attention is due to the technological and applicative solutions constituted by the ultra-thin ceramic porcelain panels developed by Cotto d’Este as a cladding for the curved walls of the tunnel. The result was the supply of 175,000 square metres of ceramic material: the largest order in the ten year history of Kerlite.
In detail, the material used is Kerlite 3Plus panels, reinforced with glass fibre on the back (total thickness 3.5 mm) in the large 100×100 cm format, for the lower section of the wall, and 100×300 cm for the top section. Kerlite was chosen for its many technical qualities, including its extraordinary flexibility which, with a radius of curvature of 5 metres, makes it perfectly suited to cladding the vault of the tunnel. The panels, in a non-reflective white, were glued to both concrete walls with special Mapei adhesives, up to a height of 4 metres from the road surface, with 10 mm joints filled with epoxy grout.
This execution fully satisfied the performance requirements of the tender specification as well as established best practice for this type of project, which gives special emphasis to the fire performance of the cladding (Kerlite is class 1),
 improvement of internal illumination, prevention and containment of water damage, improvement of acoustic comfort, and ease of use of the walls for safety and traffic signage.

Last but not least, the very competitive pricing of porcelain ceramic in comparison with conventional materials is clearly advantageous over time due to its ease of maintenance (cleaning) and service life.
In short, this ceramic application merits the epithet « underground » not only because of its location, but above all because it is a genuine alternative.