A Multi-Scale Numerical Simulation on Thermal Conductivity of Bio-Based Construction Materials

Abstract

Amid increasing concern about carbon emissions and ENERGY consumption in the building industry, bio-based construction materials are one of the solutions, especially considering their excellent thermal insulation. This study aims to develop a multi-scale numerical model to analyze the effect of microstructure on the thermal conductivity of a bio-based construction material. To achieve this, the size, shape, orientation, porosity, and water saturation of the bio-aggregate were considered in this study. The results show that the thermal conductivity of the bio-based material increases significantly and nonlinearly with water saturation, in contrast to the parallel thermal conductivity of the transversely isotropic bio-aggregate, which increases linearly. The thermal conductivity of the bio-based material shows an anisotropy in different directions and it obtains a maximum at water saturation of 0.4. Analysis of inclusions with different shapes shows that the thermal conductivity in the compaction direction is almost independent of the shape, but not in the direction perpendicular to the compaction. The finite element results show that the heat flow tends to transfer along the bio-aggregate rather than across it. These findings help to better understand the effect of microstructure on thermal conductivity and then promote the application of bio-based concrete as an insulation material in buildings.