The aggregate industry in Sweden is investigating methods to improve the quality of manufactured sand (aggregate smaller than 2 mm produced by crushing rock) for concrete production. A common way to improve the shape of the particles is to use a vertical shaft impact (VSI) crusher. However, the crushing process creates a large amount of fines (particles smaller than 63 mu m) that are not desirable in concrete mixes. The aggregate industry in Sweden is therefore investigating methods to reduce the amount of fines produced by the manufacturing of sand. One method being investigated is air classification. A centrifugal air classifier used in the aggregate industry was investigated using computational fluid dynamics (CFD) to improve the understanding of the influence of the geometric design of the classifier on the cut size and the resulting particle size distribution. Simulations were performed with a CFD model using an Euler-Lagrange approach. The simulation results show that the classification results are affected by air flow velocity, particle shape, particle size, the geometry of the air classifier and turbulence in the air flow. (C) 2014 Published by Elsevier Ltd.