Holcim Ltd - Gotthard Base Tunnel, Holcim Switzerland

The sheer scale of the venture, the multitude of issues that need to be addressed and the demanding engineering services required present tremendous challenges for all involved and make this project one of Holcim’s biggest ever. Huge quantities of rock – 24 million tons – will have to be excavated from the Gotthard Base Tunnel alone. In modern tunnel construction, excavation is increasingly done with tunnel boring machines (TBMs). The rock cut by the TBMs is very finely grained and, until recently, was unsuitable for the manufacture of high-quality concrete.

However, extensive research and testing over a period of years by AlpTransit Gotthard, in consultation with universities, research institutes and the concrete industry, eventually proved that, with state-of-the-art aggregate production plants and leading-edge concrete technology, rock chips from the TBMs can be used to produce high-quality concrete – a valuable alternative at a time when quarrying other gravel deposits is becoming increasingly difficult.

In addition, an innovative new testing system ensures the high standards required for tunnel concrete are met. Now, excavated rock is converted into around 5 million tons of concrete aggregate on-site. As a by-product, this process will yield about 0.8 million tons of extremely fine slurry, which can be used for making bricks.

Holcim Switzerland has been part of this project since the first preliminary tests for a series of special “Gottardo” cements were conducted in 1997. In Bodio, on the Gotthard Tunnel’s south side, Holcim operates its own concrete plant. This generates 120 cubic meters of fresh concrete an hour, which is transported up the mountain by special drums. Until the project is completed, Holcim will continue to provide high-quality concrete and cement for the various tunnel construction sites.