With the increasing need for underground opening's support and the increasing knowledge available today in concrete technology, shotcreting, and particularly the wet-mix process, is in great demand. Successful pumping operations however usually require a certain amount of experience. On the one hand, engineers design a mixture with high workability for ease of transport through the hose system, and on the other hand, they strive for a mixture that is relatively stiff, adhesive, and cohesive to achieve good adhesion and build-up on vertical or overhead shooting surfaces. This article presents some of the most recent research on the understanding of the key parameters affecting concrete mobility and stability under pressure, i.e. pumpability. Taking into account the mechanics of full size pumping equipment, the concept of Real Paste Content is introduced as a minimal quantity of effective paste under pressure available for mobility through a hose system. Experimental results used to validate the concept allow explanation of behavioral variations between the different concrete mixtures.
Marc Jolin, Dennis Burns, Benoît Bissonnette, Frédéric Gagnon, and Louis-Samuel Bolduc, "UNDERSTANDING THE PUMPABILITY OF CONCRETE" in "Shotcrete for Underground Support XI", Eds, ECI Symposium Series, Volume P11 (2009). http://dc.engconfintl.org/shotcrete/17