This Section of BS 812 describes a gravimetric method, based on sedimentation, for the determination of the proportion of material finer than 20 μm in particle size in aggregates. This method is not suitable for particles larger than 20 μm because of their short settling times. NOTE1 Methods for determination of particle size distribution of an aggregate down to the passing 75 μm fraction are described in BS 812-103.1. If the proportion of material between 20 μm and 75 μm is required, this may be calculated from the results of the determination carried out in accordance with this Section and BS 812-103.1. NOTE2 The titles of the publications referred to in this standard are listed on the inside back cover.