There is probably nothing as frustrating to even the most tolerant wet-mix shotcrete placing contractor or crew as problems related to pumping. While the following comments are spe-cifically related to shotcrete placement, many of them are also applicable to normal concrete pumping applications. The rheology of shotcrete mixtures is affected by the pumping pro-cess, which typically involves repetitively compressing a shotcrete mixture and forcing the mixture to the point of final placement under pressure.