Recommendations and interpretations for the tortuosity and pore-connectivity parameter in undamaged cement-based materials

Unsaturated transport properties, such as hydraulic conductivity (K), are commonly viewed as durability parameters for cement-based materials. Measuring K experimentally, however, is challenging due to high-pressure requirements at low degrees of saturation. For this reason, analytical expressions for hydraulic conductivity are often employed. Possibly the most widely used model for this purpose is the van Genuchten–Mualem equation. Usage of this equation requires employment of the tortuosity and pore-connectivity parameter I, which has significant implications on K. Often, a default value of I=1/2 is used, which leads to misrepresentation of K at low degrees of saturation. Recent works have identified the need for proper estimation of I, however uncertainty as to the realistic range for I still exists. In this paper, recommended ranges of I are developed for undamaged cement-based materials using analytical modeling based on physical realizations of unsaturated hydraulic properties. Interpretations of I are then presented based on the derived models.