Using creep and recovery to study flow behavior of fresh cement paste

Abstract A controlled stress rheometer has been used to determine the creep and recovery behavior of flocculated cement pastes. The behavior was found to depend on the level of applied stress. At a lower applied stress, the creep curve of each paste was characteristics of a nonlinear viscoelastic solid, with an instantaneous strain superimposed on an elastic strain; the recovery, on the other hand, was characteristics of a viscoelastic liquid, with little or no instantaneous strain, but some retarded strain and a substantial unrecovered strain. At a higher applied stress the behavior was strikingly different. In this case, the behavior was characteristics of a viscous liquid, with a nearly linear increase in strain throughout the duration of the stress and no recovery when the stress was released. This transition from solid-like behavior to liquid-like behavior occurred over a very narrow stress increment, and the transition stress corresponded to the yield stress estimated from flow curves and from oscillatory shear measurements.