Experimental Study of Hemp Fibers Effect on Thermal Properties of Clay Matrix

As a natural building material, clay provides excellent thermal mass, which helps regulate indoor temperature. In addition, hemp fibers are characterized by good mechanical resistance and excellent thermal insulation qualities. To promote these abundant materials in Moroccan rural areas, the impact of hemp fibers on the thermal insulation of clay was studied. Six mortars were made from local clay and varying proportions of Moroccan hemp fibers. Mass fractions of 0%, 1%, 2%, 3%, 4% and 5% clay were systematically replaced by hemp fiber and then, for each fiber content, three samples were prepared to ensure the reproducibility of the results. The thermal conductivity and volumetric heat capacity of the composite materials were then evaluated using the Hot Disk method, along with other derived properties. Experimental findings indicate that a minor reduction in density occurs with the incorporation of hemp fibers, while the thermal insulation capabilities of clay are notably improved, particularly when the fiber mass fraction ranges between 4 and 5%. Hence, with 5% fiber replacement, thermal conductivity is decreased by 53%, and heat capacity is increased by 55%. Additionally, thermal diffusivity and effusivity are decreased by 68% and 17%, respectively. Furthermore, it has been established that for a 20 cm thick wall, the thermal resistance and the diffusivity characteristic time are increased by 67% and 208%, respectively. This highlights the potential for integrating hemp fibers as a partial substitute for clay, thereby enhancing the thermal comfort and energy efficiency of prevalent constructions, particularly in rural regions.