Concrete contribution to Gotthard project - TunnelTalk
COMPANY NEWS Concrete contribution to Gotthard undertaking Oct 2010
BASF MEYCO News Release
Admixtures to optimize the use of concrete in conditions deep under the Alps, as well as shocreting machines and fire protection mortar to protect the concrete linings in the event of a fire in the tunnels, were contributions by BASF MEYCO to construction of the longest railway tunnel in the world. As the first main running tunnel of the Gotthard Base Tunnel breakthroughs, BASF recalls its supply of construction chemicals and equipment to two of five construction contracts that total about 20km of the total 57km long twin tube tunnel.

Shotcrete primary lining on a crossover cavern

To the excavation works between Erstfeld and Sedrun, admixtures were supplied to achieve high quality concrete linings for the tunnels and the cross passages that connect the tubes every 300m.
"When used underground, concrete must meet the most contradictory of requirements," explained André Germann, Manager of MEYCO Underground Construction for Germany, Austria, Switzerland and Eastern Europe. "Keeping concrete workable for hours as it is transported many kilometres into the mountain and then having it solidify in a flash as soon as it is applied to the tunnel wall was one of the greatest challenges for the Gotthard Tunnel project."
This is only made possible using the correct combination of admixtures. Various superplasticizers sold under the GLENIUM® brand make concrete especially free flowing while MEYCO® SA 160 accelerator for sprayed concrete ensures that, once applied, shotcrete solidifies in seconds.

Construction lots of the Baseline project

In order to meet the special challenges concerning the processability of concrete in the Gotthard Base Tunnel, BASF developed the DELVO® Crete Stabilizer 10. This admixture slows down cement hydration and ensures an open time of four to six hours. Combined with the GLENIUM® superplasticizers, the concrete is workable even after being transported over long distances and exposed to the high temperatures in the interior of the mountain. In the Gotthard Base Tunnel, this system of combining superplasticizers with retarding agents has been used for initial shotcrete support as well as during casting of the final concrete lining.
To two construction contracts between Erstfeld and Sedrun in the northern part of the tunnel, BASF MEYCO® supplied MEYCO® Potenza and MEYCO® Oruga shotcreting spraying units for application of reinforced primary lining shotcrete immediately behind the advancing TBMs. The process ensured rapid support of the excavation and a safe working environment for the tunnelling crews.
MEYCO® Fireshield 1350 fire protection mortar manufactured by BASF was supplied to protect the concrete tunnel lining of the Bodio tunnel section near the southern portals.
Application of this special fire protection mortar was required, since fire temperatures exceeding 300°C leads to concrete spalling. At temperatures above 1,000°C it loses its load-bearing capacity altogether and the tunnel may collapse.
"Being covered with a layer of fire protection mortar the tunnel walls can withstand temperatures of up to 1,400°C for a minimum of 90 minutes," said Frank Clement, BASF expert for underground fire protection solutions. "This gains precious time for fire fighting."

Cast concrete final lining

A specified thickness of Fireshield 1350 was applied to the final concrete linings of the tunnels using MEYCO® Suprema spraying units and a MEYCO nozzle system adapted specifically for application of fire protection mortar.
When the the Gotthard Base Tunnel opens in 2017, travel time between Zurich and Milano will be shortened by one hour. In addition, freight trains will be able to travel the straight, flat tunnel alignment with twice the load and at twice the speed. People and goods will cross the Alps faster, more safely and in a much more environmentally friendly way. The breakthrough today of the first running tunnel of the twin tubes through the base of the Alps is a historic and record beating achievement.
References
History in the making at St Gotthard - TunnelTalk, Oct 2010

           

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