Approches micro-macroscopiques pour l’évaluation des mécanismes fongiques impliqués dans la dégradation des mortiers biosourcés : impact sur les propriétés hygrothermiques

The main objective of this thesis work was the study of the durability of bio-based materials such as hemp mortar in the broad sense. The aspects of aging and different factors influencing the performance of hemp mortar during its period of use were taken into account.The originality of this work lies in several aspects. On the one hand, it is a study of the aging of hemp mortar. To do this, it is necessary both to adopt an aging protocol representative of the conditions of use of hemp mortar and to use different experimental methods to monitor the evolution of characteristics and properties. All this work has led to the implementation of specific setups for the application of aging cycles.On the other hand, the in-depth study of the microbial proliferation is necessary to palliate the fact that the hemp mortar represents a great risk of microbial growth because of its organic nature. For this purpose, the use of analytical methods rarely used in the civil engineering environment was adopted (DNA extraction and sequencing).First, the accelerated aging protocol was proposed which aimed to better represent the usage conditions considering the constructive information of the hemp mortar installation. To analyze the influence of aging, several experimental devices were adopted. This allowed to study the evolution of microstructure, chemical composition and hygrothermal properties.Then, the microbial contamination was studied from different points of view. First, the influence of fungal growth on the chemical composition was studied. This work required the study of the conditions of growth of moulds and the implementation of an experimental protocol allowing the analysis and the comparison of the evolution of the composition of raw and contaminated mortars. Then, different identification methods were proposed to understand the nature of the fungal contamination. First, phenotypic identification was applied to analyze the fungal contamination. Then, another method, proposing a fine screening technique of fungal and bacterial contamination, was used to obtain the most reliable results.