Gelation, Shear-Thinning and Shear-Thickening in Cement Slurries

The rheological behavior of cement slurries may be described in terms of a few elementary behaviors: - the rapid formation of a gel, at rest; - the collapse of this gel under a critical stress directly related to the strength of the interparticle forces; - the progressive destruction of the gel fragments under moderate shear rate, with an increasingly shear-thinning behavior as the elementary particles gets smaller; - the reconstruction, at high shear rate, of shear-resistant structures, probably as chains of grains at contact; - complete jamming, possibly. We analyze the transition mechanisms from one step to the next one. We show how the addition of a dispersing agent favors shear-thickening at the expense of shear-thinning and how the control of the particle surface state and of interparticle friction restricts shear-thickening and the risk of jamming.