The particle-fluid and particle-particle interactions governing the flow of highly concentrated power plant ash slurries containing fine-grained and coarse-grained ash particles have been investigated. The friction mechanism and suspension of coarse bottom ash fractions conveyed in a finer fly ash slurry vehicle were analyzed using the rheological and pipeline experimental data in a solid concentration range of 62.5-67.5% by weight. The degree of homogeneity and possible heterogeneously distributed solid fraction for the mixture slurry along the vertical axis of the pipe were evaluated using the well known Ismail's equation. A nearly non-settling nature of the pseudo-homogeneous mixture slurry at high solid concentration under laminar pipe flow regime has been observed. It has been determined that this sort of response is mainly due to the presence of granular Coulombic and Bagnold forces. (C) 2013 Elsevier B.V. All rights reserved.