The paradox of self-compacting concrete : why does it require more energy during pumping ?

Due to its low yield stress, Self-Compacting Concrete (SCC) can fill a formwork almost perfectly without the application of any external energy, making SCC very advantageous for construction. From the experience on the worksite, it can be concluded that concrete pumps need a larger amount of energy to placer SCC compared to traditional (vibrated) concrete, although SCC is apparently more fluid than TC. In this paper, after a short introduction on the rheological behaviour of SCC, the analysis of full scale pumping tests shows the answer : Due to the higher viscosity, needed to avoid segregation of SCC, the pressure demands for high-speed flow are higher when compared to TC. As a solution, the viscosity could be lowered, but as a consequence, yield stress must be increased, which might lead to an incomplete filling of the formwork