This paper has investigated the effect of solids concentration and the addition of a dispersant called Dispersant S40 on the flowability of unground and ground limestone slurries. The rheological behaviour of the unground slurries (<100 μm) is transformed through different types of flows with increasing solids concentration. The use of Dispersant S40 can improve the slurry flowability by decreasing viscosity and eliminating Bingham yield stress. The rheological behaviours of ground limestone slurries vary with grinding from a starting dilatant flowability to a resulting pseudoplastic one with an evident Bingham yield stress combining a thixotropic character, whose appearance is correlated to the fineness of a ground product, solids concentration, and the additive amount of Dispersant S40. In addition, the accurate rheological characterization of time-dependent fluids is dependent upon the used instruments and operation conditions.