Innovative Thermal Conductivity Analysis of Castable Materials via Spherical Geometry: Preliminary Study

This preliminary study introduces a cost-effective and innovative methodology for characterising the thermal conductivity of mortars, addressing the limitations of traditional steady-state methods. The proposed approach utilises a spherical specimen geometry to ensure perfect symmetry and isolate one-dimensional (1D) radial heat flow, effectively overcoming common issues related to surface contact resistance and edge effects. The research evaluates and compares three numerical models – Fourier, Maxwell-Cattaneo, and temperature-dependent λ(T) – against experimental transient data obtained during the cooling phase of various lime-based mortars. The results demonstrate that all models provide optimal fits (R2 > 0.999), with the λ(T) approach proving particularly robust in capturing the dynamic thermo-dependent behaviour of bio-based composites. The derived dry-state thermal conductivity values are consistent with the density-dependent trends reported in EN 1745:2020. This methodology offers a straightforward and accurate tool for generating thermal parameters for building energy simulations. Finally, this work lays the foundation for future applications of spherical transient analysis to complex surface morphologies, suggesting a potential pathway to bridge the gap between intrinsic material properties and the thermal performance of finished building components.