The properties of cementitious materials in their dry state and their influences on viscosity of pastes were studied. The cementitious materials considered were Portland cement, fly ash, and ground granulated blast furnace slag (GGBFS). Both plain and blended mixes were tested, where plain mixes were made of a single material, while blended materials were made of the Portland cement blended with either fly ash or GGBFS. The properties tested for dry cementitious materials included the compression, recompression, swell indices, stiffness modulus, and coefficient of friction as well as the density and void ratio of gently consolidated bulk materials. Viscosity of the pastes, made with the plain and blended cementitious materials at a water-to-binder ratios (w/b) of 0.45 and 0.55 by weight, were measured. Correlations between the properties of the dry materials and viscosity of the pastes were analyzed. The results indicate that the size, shape and angularity of the cementitious materials greatly affect their dry-state properties as well as the flow behavior of the pastes. Cementitious materials that consolidate well in their dry state will produce a less viscous paste. A decrease in dry coefficient of friction and an increase in stiffness modulus will result in a decrease viscosity of the paste. (C) 2012 Elsevier B.V. All rights reserved.