Numerical Analysis of the Thermal Properties of Ecological Materials Based on Plaster and Clay

Most of the energy savings in the building sector come from the choice of the materials used and their micro-physical properties. In the present study, through numerical simulations a link is established between the thermal performance of composite materials and their microstructures. First, a two-phase 3D composite structure is mod-eled, then the RSA (Random Sequential Addition) algorithm and a finite element method (FE) are applied to eval-uate the effective thermal conductivity of these composites in the steady-state. In particular, building composites based on gypsum and clay, consolidated with peanut shell additives and/or cork are considered. The numerically determined thermal conductivities are compared with values experimentally calculated using the typical tools of modern metrology, and with available analytical models. The calculated thermal conductivities of the clay-based materials are 0.453 and 0.301 W.m-1.K-1 with peanut shells and cork, respectively. Those of the gypsum-based materials are 0.245 and 0.165 W.m-1.K-1 with peanut shells and cork, respectively. It is shown that, in addition to its dependence on the volume fraction of inclusions, the effective thermal conductivity is also influenced by other parameters such as the shape of inclusions and their distribution. The relative deviations, on average, do not exceed 6.8%, which provides evidence for the reliability of the used approach for random heterogeneous materials.