Analyse of the Evolution of the Hygrothermal Properties of the Hemp-Based Mortar within the Framework of the Total Weathering Protocol

The use of bio-based composites for building insulation is interesting from the point of view of hygrothermal performances, economic and environmental benefits. Among different organic fibers for these materials, hemp is interesting because of its huge availability in France. Nevertheless, the broad application of the hemp-based insulation mortars is hampered due to the lack of a database on their durability. This paper consists of a better understanding of the evolution of the hemp-based composite and its hygrothermal properties. The main objectives are, first, to study the evolution of the hemp insulation mortar microstructure and properties under the accelerated aging cycles, and second, to characterize and analyze the interconnection between observed changes. Experimentally, the protocol of accelerated aging inspired by standardized one was proposed, the microstructural characteristics and the hygrothermal properties, as the total porosity, the thermal conductivity, and the moisture buffer value (MBV) before and after the aging cycles was identified. The MBV characterization was performed for both hemp mortar and hemp shives. The obtained results reveal the increase of the hemp mortar porosity and the decrease of the hemp mortar's thermal conductivity. Furthermore, the MBV value of hemp mortar changes slightly, unlike that of the bulk hemp, which is explained by the mineral matrix's influence. These results consist of data for a better forecast on the degradation of the hemp mortar.