November 17-20, 2019
Tunneling construction engineering cannot exist without sprayed concrete – whether it is in tunneling, mining or equivalent constructions. Underground construction is a vast field and will be of strategic urban importance in the future. On the one hand, many existing tunnels will need in short term repair work or enlargements, while there is huge demand for the construction of new ones.
Polymer-modified sprayed concrete is suitable for the most used wet shotcrete application, but, as it is also common to use dry shotcrete, it’s also possible to be used there.
The used polymer amount depends highly on the requirements, in terms of the levels of strength, stability and water impermeability. The application of modern shotcrete needs to reduce rebound from the spraying, which is a time, cost and environmental factor due to the loss of material and changes of concrete properties, and polymer-modification is an interesting possibility to achieve the target. Modifying sprayed concrete with polymers reduces material consumption and improves spraying efficiency and durability.
The technical performance of wet or dry sprayed concrete demonstrated and measured under real application conditions proved the positive effect of polymers in sprayed concrete.
A description of review of field tests and reference projects will be provided, an overview of possible applications, usage and advantages where polymer-modified sprayed shotcrete was applied.
- At a salt mine wet sprayed concrete was used, reported earlier in Davos in 2009, when groundwater seeped into the middle of the tunnel. By modifying the regular concrete formulation with polymer binders, the processing was secured, a 10 year field report.
- At the Hagerbach test Gallery, a field test with wet shotcrete proofed the water tightness performance.
- At a pressure water tunnel logistics were critical for project realization, and the reduction of rebound – realized with dry sprayed concrete – improved the project’s progress.
- At a water canal polymer modified dry sprayed concrete was used to strengthen the flanks against elevated water pressure.
Klaus Bonin, "Performance Improvement of Shotcrete by Polymer Binder Modification" in "Shotcrete for Underground Support XIV", Matthias Beisler, ILF Consulting Engineers Asia, Ltd., Thailand Preedee Ngamsantikul, Thailand Underground and Tunneling Group (TUTG), Thailand Herbert Klapperich, TU Freiberg, Germany Eds, ECI Symposium Series, (2019). https://dc.engconfintl.org/shotcrete_xiv/15