Ultra high performance cementitious materials possess high solid volume fraction by a decreased water-to-binder ratio. The use of a high-range water reducing admixture allowed us to obtain the initial fluidity of ultra-high performance cementitious materials, but its poor workability and significant loss of fluidity remained. Incorporating a high volume of supplementary cementitious materials reportedly weakens workability because they reduce the plastic viscosity of a mix. Hence, in this research, waste limestone powder was tested to evaluate its effect on the rheological properties of cement paste. The results give new insight on controlling the fluidity and plastic viscosity when preparing the mix for ultra-high performance concrete.