Prediction of the maximum packing volume fraction with non-spherical particles has been one of the important problems in powder technology. The sphericity depending on the particle diameter was measured by means of an image processing instrument. An algorithm to predict the maximum packing volume fraction with non spherical particles is proposed. The maximum packing volume fraction was used to predict the slurry viscosity under well dispersed conditions. For this purpose, Simha's cell model was applied for concentrated slurry with wide particle size distribution. Also, Usui's model developed for aggregative slurries was applied to predict the non-Newtonian viscosity of dense fly ash-water slurry. It was certified that the maximum packing volume fraction for non spherical particles can be successfully used to predict slurry viscosity, and this means indirectly the maximum packing volume fraction determined in this study is reasonable.