Making the Old Meet New Standards

Times change and physical structures need to change with the times. To keep up with the newest rules and regulations, structures often need to be modified. As nations move to unified regulations in the EU (European Union), non-EU countries with contingent borders have to adopt the rules or be excluded from the trade and commerce that they would benefit from otherwise.
Switzerland, while not an EU member state, has bilateral treaties with the EU for trade and the nation has adopted many of the EU laws to participate. At times, those rules require significant investment in infrastructure. One such case is the standardization of railroad cars for movement of goods and material across the many borders along the EU’s 27 member countries. As an example, the standard container freight car requires tunnels to have a minimum of four meters (approximately 13-ft.) corner height to accommodate trains passing on parallel tracks within the structure.
In operation since 1874, the dimensions of the Paradiso Tunnel (757 m/2,500-ft. long) did not allow the four-meter (13-ft.) corner height. The double-track railway tunnel connects the Swiss municipalities of Paradiso and Lugano (Canton Ticino) and is a key part of the Gotthard Pass transport artery, the flat route through the Alps that forms the heart of the European freight corridor between Rotterdam in the North and Genoa in the south, allowing more freight to be transported by rail and thus contributing to the protection of the Alps and to increasing the switch of international freight traffic from the road to the rails by allowing rail transit of standardized containers.
To realize a four-meter corridor along the entire length of the Gotthard route, about 20 tunnels are currently being enlarged, along with alterations to platforms, traction current systems, signaling installations, and overpasses by the Swiss Federal Railways or as the Swiss refer it SBB.
The Paradiso Railway Tunnel construction project, completed in December 2020, opens the next phase of Switzerland’s crucial Gotthard railway line to standardized freight cars. The SBB realized that the project would require more than just blasting and drilling to make it safe and reliable for generations to come. It needed an improved shotcrete mix to ensure impermeable and durable tunnel walls, and this was true for all the tunnels along the Gotthard rail line. The IMM (Meccanica dei Materiali), a Swiss materials technology laboratory, was commissioned by the SBB to analyze and propose a solution that would also integrate self-healing capabilities for the resulting concrete structures.
In the search for a robust waterproofing solution, the IMM experts subjected samples of both PENETRON ADMIX-treated and untreated concrete to extensive lab tests:
Water permeability under hydrostatic pressure (EN 12390-8) on treated and untreated concrete samples (without accelerant)
Self-healing properties of treated concrete samples (with and without accelerant)
These tests analyzed self-healing capabilities (through continuous flow measurement tests and microscopic analysis of the concrete samples) to verify both impermeability and durability characteristics (according to SIA 262/1 standards) under the high hydrostatic conditions of a subterranean tunnel. The test results showed that adding PENETRON ADMIX to concrete enabled the concrete matrix to seal cracks up to 0.5 mm, without adversely effecting any other concrete properties. Chloride diffusion and the carbonation coefficient (under cyclical dry/wet test conditions) were also improved.
Construction work began in late 2018 and was completed in late 2020. The main construction phase of the new, taller Paradiso Tunnel was the application of the Penetron shotcrete proposed to the SBB engineers by IMM and Penetron Italia. Once sprayed on the tunnel wall superstructure, it prevented any water infiltration from the backfill side.