Matches in UGent Biblio for { ?s ?p Pumping of concrete is a frequently applied casting process. For traditional concrete, slump losses have been reported in literature, but the real cause is still unknown. In case of self-compacting concrete, it is not known at all how the fresh properties evolve due to pumping. This paper will describe the evolution of the fresh properties of SCC due to pumping operations, in which the velocity is increased stepwise. Two different effects modify the fresh properties: structural breakdown and an increase in air content. Both effects cause a decrease in viscosity, which is translated in a lower V-funnel flow time and lower pressure losses during pumping. On the other hand, structural breakdown and the increase in air content have an opposite influence on the yield stress. If structural breakdown dominates, the yield stress decreases, if the effects of the increase in air content dominate, yield stress increases. In the first case, as both yield stress and viscosity decrease, segregation can be provoked. In the second case, due to the increase in yield stress, the filling ability of the SCC is reduced, which can lead to improper filling of the formwork. The results show a trend that the more fluid SCCs tend to segregate and the less fluid SCCs tend to loose even more fluidity. Furthermore, the magnitude of these effects appears to increase with increasing velocity in the pipes.. }
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- aggregation abstract "Pumping of concrete is a frequently applied casting process. For traditional concrete, slump losses have been reported in literature, but the real cause is still unknown. In case of self-compacting concrete, it is not known at all how the fresh properties evolve due to pumping. This paper will describe the evolution of the fresh properties of SCC due to pumping operations, in which the velocity is increased stepwise. Two different effects modify the fresh properties: structural breakdown and an increase in air content. Both effects cause a decrease in viscosity, which is translated in a lower V-funnel flow time and lower pressure losses during pumping. On the other hand, structural breakdown and the increase in air content have an opposite influence on the yield stress. If structural breakdown dominates, the yield stress decreases, if the effects of the increase in air content dominate, yield stress increases. In the first case, as both yield stress and viscosity decrease, segregation can be provoked. In the second case, due to the increase in yield stress, the filling ability of the SCC is reduced, which can lead to improper filling of the formwork. The results show a trend that the more fluid SCCs tend to segregate and the less fluid SCCs tend to loose even more fluidity. Furthermore, the magnitude of these effects appears to increase with increasing velocity in the pipes.".