Low Cement Content Shotcrete: A Comparison


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Title: Low Cement Content Shotcrete: A Comparison

Author(s): F. J. Wombacher, U. Maeder, and M. Sommer

Publication: Special Publication

Volume: 212


Appears on pages(s): 1005-1018

Keywords: cement content; durability; pumping; shotcrete; superplasticizers

Date: 6/1/2003

Shotcrete is used worldwide be it for ground strengthening, for tunnel and/or mining applications. Due to the desired properties such as pumpability, reduced rebound, strength development and durability aspects of the shotcrete, usually a higher amount of cement is used than in normal concrete applications. However the necessity of it is not always obvious. Shotcrete mixtures with a range of reduced cement contents are studied in large scale trials using pumping aids. Partially cement was replaced by fly ash and burnt oil-shale. The mixtures are accelerated with an alkali-free powder accelerator. Apart from the fresh and hardened shotcrete properties, the pumping pressure was monitored and the leaching behaviour was investigated. Durability aspects such as sulfate resistance and water impermeability of the mixtures were evaluated. All the results indicate that the use of well proportioned mineral admixtures in combination with the correct chemical admixtures, like high-range water reducers, pumping aids and environmentally friendly alkali-free accelerators, allows the production of well performing and durable shotcrete with a cement content that can be reduced by 50%.