Abstract
The improved fluidity of self-consolidating concrete by using chemical admixtures sometimes causes stability problems. In this paper some fundamentals of particle settling theory, such as Stokes’ law, are used to investigate particle sedimentation. Some preliminary calculations of stresses from particles (>0.125mm, 4.925E-4in.) on matrix (liquid and powder<0.125mm) with viscous fluid properties, indicate that yield stress is more important than plastic viscosity for the stability of aggregates when settling in matrix. The Kozeny-Carman equation (KCE) is used to analyse bleeding rate of fresh matrix with three main factors involved: solid fraction, specific surface area and liquid viscosity. Different stabilizing mechanisms of viscosity modifying agents (VMA) and fillers are also reviewed. Finally a settlement model is set up for further investigation.