In this paper we describe how the rheological properties of self-compacting concrete (SCC), namely its yield stress and plastic viscosity can be accurately estimated.Currently these properties are measured using a rheometer, but these measurements are unreliable because they are very different depending on the rheometer used.This is to do with the heterogeneous nature of the SCC mix.To get a reliable estimate of these properties,a micromechanical procedure is described for estimating the plastic viscosity of the heterogeneous mix from the plastic viscosity of the homogeneous viscous paste and the mix composition.The yield stress on the other hand is estimated in an inverse manner from the measured t5oo and flow spread of the mix in a cone flow test using the three-dimensional smooth particle hydrodynamics (SPH) method for simulating the flow of SCC.