BASF had a crucial impact in ensuring the solidity and durability of the world’s longest railway tunnel

The 57 km long tunnel – similar to the distance between Bucharest and Ploiesti – was officially opened after 20 years of construction, the investment amounting to €9 billion. This route through the Alps will reduce travel time between Zurich and Milan by around one hour. BASF had a crucial role in ensuring the solidity and durability of the tunnel by supplying the concrete admixtures, cement injections to stop water ingress, and fire-protection mortar that went into the consolidation of the 4 million metric tons of concrete – roughly 40 times as much as was used in Burj Khalifa, the world’s highest building. “We are proud that we were able to contribute our innovative solutions and know-how to help our customers master the challenges of this monumental construction project,” said Ralf Spettmann, President of the Construction Chemicals division at BASF.

Fire protection with BASF

Fires are a major danger in tunnels and there are strong fire safety requirements. If concrete gets hotter than 1,000°C, it loses its load-bearing capacity and the tunnel collapses. The wall of the Gotthard Base Tunnel near the south portal was therefore coated with a special fire protection mortar, MasterRoc FP 1350 from BASF. “With this product, the tunnel walls can withstand temperatures of up to 1,400°C for at least 90 minutes. This is valuable time for fire-fighting operations,” said Frank Clement, a BASF expert for fire protection solutions in underground construction.

Concrete solutions for deep shafts

Two vertical shafts descend more than 800 meters from the mountain village of Sedrun into one of the two multifunction stations in the tunnel, which serve as emergency stops and house ventilation equipment and other technical infrastructure. BASF solutions can also be found here: Just like the tunnel, these were first secured with sprayed concrete and then outfitted with a wall of poured concrete. “Transporting the concrete via a vertical downpipe through the shafts was particularly challenging. We had to make sure that while the concrete fell down, its components did not segregate from each other,” explained Bolliger. By choosing the right MasterGlenium concrete superplasticizer and finding the optimal dosage for the application conditions, BASF experts ensured that the concrete was still easily workable after falling freely for several hundred meters. To prevent water ingress, the microcement MasterRoc MP 650 was also injected into rock crevices and cavities.

Long distances and high temperatures in the tunnel

In the 20 kilometer section between Erstfeld and Sedrun, the two parallel tunnel tubes and the connecting galleries that link the two tunnels approximately every 300 meters were built using BASF concrete admixtures. “In underground construction, there are contradictory demands on concrete: While being transported several kilometers deep into the mountain, it has to remain workable for hours and cannot solidify. But the concrete also has to set almost immediately when sprayed onto the tunnel wall. In the Gotthard Base Tunnel this was one of the greatest challenges,” said René Bolliger, head of the Underground Construction unit at BASF for Germany, Austria and Switzerland. This was made possible thanks to the right combination of BASF concrete admixtures: MasterGlenium superplasticizers make the concrete especially flowable and workable, while shotcrete accelerators from the MasterRoc SA product range cause the concrete to solidify and harden within seconds after being sprayed on the tunnel wall. Furthermore, BASF developed an admixture in the MasterSet product family especially for the construction of the Gotthard Base Tunnel which considerably slows down cement hydration. In combination with the BASF superplasticizers, it ensured the concrete could be used optimally even after being transported long distances and exposed to the high temperatures in the interior of the mountain. “We are constantly working on innovations to make our customers even more successful. Our latest example for underground construction is MasterEase UG 3904. One advantage of this plasticizer is that, when paired with an alkali-free shotcrete accelerator, it is even easier to mix and pump,” said Bolliger. 

About BASF

At BASF, we create chemistry for a sustainable future. We combine economic success with environmental protection and social responsibility. The approximately 112,000 employees in the BASF Group work on contributing to the success of our customers in nearly all sectors and almost every country in the world. Our portfolio is organized into five segments: Chemicals, Performance Products, Functional Materials & Solutions, Agricultural Solutions and Oil & Gas. BASF generated sales of more than €70 billion in 2015. BASF shares are traded on the stock exchanges in Frankfurt (BAS), London (BFA) and Zurich (AN).