Parameters influencing pressure during pumping of self-compacting concrete

The main difference between conventional vibrated concrete (CVC) and self-compacting concrete (SCC) is observed in the fresh state, as SCC has a significantly lower yield stress. On the other hand, the placement of SCC by means of pumping is done with the same equipment and following the same practical guidelines developed for CVC. It can be questioned whether the flow behaviour in pipes of SCC is different and whether the developed practical guidelines can still be applied. This paper describes the results of full-scale pumping tests carried out on several SCC mixtures. It shows primarily that the slump or yield stress of the concrete is no longer a dominating factor for SCC, as it is for CVC. Instead, the pressure losses are well related to the viscosity and the V-funnel flow time of SCC. Secondly, bends cause an additional pressure loss for SCC, which is in contrast to the observations of Kaplan and Chapdelaine and the estimation of the practical guidelines is not always on the safe side. Finally, due to the specific mix design of SCC, blocking is less likely to occur during pumping operations, but the same rules as for CVC must be applied during start-up.

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