The heterogeneous nature of bleeding in cement pastes

We focus in this paper on the bleeding of cement pastes. Our experimental results suggest that bleeding cannot be simply considered as the consolidation of a soft porous material but is of an obvious heterogeneous nature. It indeed leads to the formation of preferential water extraction channels. We measure here the existence of an induction period. This period could, if fully understood and extended, be of major interest from an industrial point of view. It is followed by an accelerating period, during which the apparent permeability of the paste increases due to the formation and percolation of the water extraction channels. The water is then extracted at a constant rate until gravity is not able to further consolidate the zones located between the channels. Only this later regime had been observed and discussed until now in literature. (C) 2017 Elsevier Ltd. All rights reserved.