Prediction model of the mortar's yield stress based on the aggregate's volume fraction and properties

Yield stress is an important performance parameter for cement-based materials. Nonetheless, the prediction and regulation of the yield stress using current models still requires the execution of the rheological tests at the corresponding scales (mortar or concrete), which is time-consuming and costly. This paper proposes a model for cement-based materials' (at the mortar scale) yield stress based on theoretical analysis and a multi-scale approach. This model demonstrates that mortar's yield stress can be expressed as a function of the aggregate's properties (specific surface area, volume fraction, size, and packing density) and the yield stress of a cement paste with the same water-to-cement ratio as the mortar. In addition, the model's fitting parameters are fixed for different types of aggregates. Validation tests revealed that the proposed model can accurately predict the mortar's yield stress. Finally, a relationship between relative yield stress and relative plastic viscosity is established, providing useful information for regulating the rheological properties of a given mortar.