IDD prediction model of thermal conductivity of wet cement mortar with mixed defects of cavities and cracks.

This article focuses on developing a prediction model for the equivalent thermal conductivity of cement mortar containing mixed defects—specifically cavities and cracks—under varying moisture saturation degrees. Using the Interaction Direct Deduction (IDD) homogenization method, the model accounts for the random distribution, shape, and saturation of these defects, treating water and air within defects as two-phase media. The model’s accuracy was validated through numerical simulations, showing that thermal conductivity decreases with increasing defect content and cavity-to-defect ratio, while it generally increases with higher saturation degrees, especially beyond 80%. The proposed model offers a physically grounded, simple approach suitable for engineering applications and provides theoretical support for studying thermal conductivity in damaged cement-based materials and composites with linear and spherical inclusions.