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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Title: Minimization of Leaching of Shotcrete by Admixtures
Author(s): R. Breitenbucher, R. Springenschmid, and H. W. Dorner
Publication: Special Publication
Appears on pages(s): 781-794
Keywords: accelerating agents; admixtures; alkalies; drains; fly ash; leaching; moisture; shotcrete; silica fume; slag cements; tunnels; Materials Research
Abstract:In tunnels built according to the New Austrian Tunnelling Method, the shotcrete shell is often in contact with ground water. Depending on the amount and type of water, chemical compounds in the shotcrete are dissolved and transported into the drainage pipes and the main outfall. Due to precipitation of the dissolved compounds, the maintenance of the drainage systems is very expensive. Furthermore, the main outfall is loaded with water of a high pH-value. It was found that as well as Ca(OH)2, the alkalies in the shotcrete are responsible for the degree of leaching. Therefore, the accelerators needed for such shotcretes, which are based mostly on alkalies, have to be reduced as much as possible. This can be done sufficiently if silica fume is used in connection with slag cement to make the shotcrete sticky enough, so that it adheres to the rocks.
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