Gotthard Base Tunnel

The client AlpTransit required a 100-year service life without significant maintenance to the concrete, i.e. de facto 100-year durability for the concrete and the waterproofing systems. For the first time the client specified a prequalification process under which bidders had to qualify separately over three stages for the works on all five of the project construction contracts:

• Stage 1: Aptitude certification; technical and production certification “Stage 1 Application Documents March 1996”.
• Stage 2: Preliminary tests; independent completion of concrete tests with original aggregates, but without having to comply with difficult temperature conditions; results determining who could participate in the main tests.
• Stage 3: Main tests; production of concrete grades OB 1 & 2 and SB 1 & 2 under the client’s supervision, complying with all the external conditions; successful results were the basis for inclusion in the list of grades in the tender documents.
  

On large tunnel construction sites, the main works of tunnel excavation, stabilization, waterproofing and lining are accompanied by an almost endless series of other works, from minor concrete repairs to complete flooring systems, railfixing or fire protection. The main works such as the concrete, sprayed concrete concepts and tunnel waterproofing systems, are determined in complex preliminary tests before the final contracts are awarded (such as in the case of the Gotthard Base Tunnel by the prequalification process), but the solutions for the many other works have to be found quickly on site. Concepts and products are then evaluated and tested by site and the rest of the professional team.

In total, Sika supplied more than 40,000 tons of products, including over 3 million m² of waterproofing systems. The most significant Sika products and systems supplied are listed briefly below, although there were also many more everyday products and systems used as well.