Abstract: A series of rheometric tests was conducted on raw cement at different concentrations and particle finesses as well. The paste of raw cement, formed by a set of particles suspensions in water, presents rheological properties that make it different from the fluids commonly used. The obtained results have showed that the rheological behaviour is the shear-thinning type and can be described satisfactorily by a model of Herschel-Bulkley, characterized by three parameters τ0, K and n which connect the shear stress to the shear rate. In addition, the parameter τ0 was correlated by an exponential function of the volume concentration of particles, this correlation is valid for both the raw cement and limestone. This latter is the main component of raw cement, for that reason its rheology has been studied.