Towards better characterizing thermal conductivity of cement-based materials: The effects of interfacial thermal resistance and inclusion size

Highlights: • Interfacial thermal resistance and inclusion size impact thermal conductance. • Interfacial resistance affects thermal conductance through coarse aggregates. • Decreasing the size of aerogels reduces thermal insulation efficiency. • The findings improve the designs of thermally insulating materials. Approaches based on effective medium theories (EMTs) have been widely applied to estimate the thermal properties of cement-based materials in multi scales, but some important affecting factors remain still far from being fully understood. Herein we focused on the effects of interfacial thermal resistance and inclusion size that were often ignored before on the thermal conductivity of cement-based materials. By using EMT-based multi-scale micromechanical approaches and Mori-Tanaka (MT) upscaling scheme, we analyzed and discussed how inclusion size and interfacial thermal resistance affect the effective thermal conductivity of an inclusion-matrix system. Comparative studies on different types of cement-based materials (i.e., cement pastes, ordinary and aerogel concretes) were performed to quantify the contributions of inclusion size and interfacial thermal resistance. The results showed that interfacial resistance plays an important role on predicting the effective thermal conductivity of cement-based materials with coarse inclusions, while the size effect operates for those with fine inclusions. The findings of this study help predict the thermal properties of old cement-based materials accurately and design new thermally insulating cement-based composites rationally.