Rheology, or flow behavior, plays a vital role during fresh-state applications of cement composites. Understanding and controlling cement rheology are gaining significant attention for emerging construction practices like 3D printing. Literature defines cement rheology using one of the four mathematical models, i.e., Bingham, modified Bingham, Herschel–Bulkley, and Power law. The models defined in the literature are based on the shear stress and shear rate relationship and fail to account for temporal changes, like cement hydration. Cement hydration results in internal structural buildup with time, typically increasing the shear resistance. This effect is opposed by the breakdown caused by the applied shear rate. The combined effect of buildup and breakdown depends on cement hydration, time of observation, and applied shear rate. Existing models fail to explain the overall cement rheology across a long time span and a wide range of shear rates. As a result, literature often explains cement rheology using contradictory phenomena like thixotropy–rheopexy. The present study overcomes this challenge by presenting a novel mathematical model for cement rheology, which can account for the temporal effect of buildup and breakdown. The mathematical model is developed from an extensive experimental investigation of cement rheology across a wide range of shear rates and long time spans. For the first time, the mathematical model simultaneously explains buildup and breakdown mechanisms. The novel mathematical model includes temporal effects and can serve as the foundation for reimaging cement rheology for emerging construction practices.