Erstfeld-Bodio, Switzerland

When the Base Tunnel officially opened on June 1, 2016, the Gotthard - the barrier between north and south - was finally conquered. Thanks to the longest rail tunnel in the world, trains now race through the Alps and scarcely have to climb - setting a milestone in transport and for the mobility of the future.

Project Requirements

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.

Sika Solutions

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.

Project Participants

AlpTransit Gotthard AG

SikaBau AG, Consortium TAT, Zschokke Locher AG, Consortium IGS, Tecton AG

Sika Organization
Sika Schweiz

Products Used

Sprayed concrete (SB), blasting and TBM drilling

Sika® ViscoCrete® SC Plasticizer
SikaTard® Retarder
Sigunit® Accelerator
SikaFume® Concrete additive
SikaPump® Start-1 Pumping agent
FlexoDrain W Channels
Sika® PM-500 PC sprayed concrete system
Sika® PM-702 Concrete pump
Aliva®-503 Concrete spraying machine
Aliva® L-1/L-2 TBM sprayed concrete system
Aliva® AL-278 Concrete pump
Aliva® AL-403 Dosing unit

Site-placed concrete (OB)

Sika® ViscoCrete® Plasticizer
SikaTard® Retarder
SikaPump® Pumping agent
SikaPump® Start-1 Pumping agent
SikaFume® Concrete additive
Sika® Separol® W Formwork release agent
Sika® Mixer Protector, Surface protection

Immediate stabilization and anchor bonding at critical points

Sika® Rock Shot-3 Dry sprayed mortar
Sika AnchorFix® Anchor adhesive
Sika® Intraplast® Injection additive
Sika® Fix T-10 RX Injection resin
SikaCem®-501 Rapid hardening cement
Aliva®-252 Concrete spraying machine 

Waterproofing of tunnel structures

Sikaplan® Sheet waterproofing membranes
Sarnafil® Sheet waterproofing membranes
Sika® Waterstops
Sikaplan® W Felt Protective geotextile
Sikaplan® WT Tape jointing system
Sika® Trapezoidal Profiles-Formwork inserts
Sikadur-Combiflex® System Joint waterproofing
SikaSwell® Sealing profiles

Everyday support

Sika MonoTop® Patching mortar
Sikadur® Repair mortar
Sika® FastFix Rapid hardening mortar
Sika®-4a Rapid hardening binder
SikaGrout® Grouting mortar
Sikafloor®-2530 W Floor coating
Sikaflex®-11 FC Sealant
Sika Boom® Foam filler