No abstract

Spruce wood, as all biosourced materials, is very sensitive to relative humidity changes, which can cause dimensional variations. In some cases, it leads to eccentricity, degradation and deterioration of the wooden structures. The 3D methods of evaluation of the spruce wood hydric behavior needs important financial resources and investigation. That's why, the main objective of this study is to develop the technics of 2D digital image correlation to estimate the local displacements and strains values under hydric solicitations and to follow the hysteresis phenomenon, anisotropy and swelling coefficient. In this context, cycles of sorption -desorption for relative humidity that vary from 0 to 100% were applied. Results represent swelling coefficients for early-and latewood as a function of wood directions. A particular attention was devoted to the uncertainty of the 2D digital image correlation technics for both earlywood and latewood. This study provides the literature and future research with promising results especially concerning the evolution of the microscopic morphology of biosourced materials when exposed to relative humidity variations, which can significantly affect their macroscopic behavior.

The use of hemp mortar as a bio-based insulation composite is widely promoted in the construction sector in France due to its environmental and hygrothermal advantages and the availability and low price of hemp fibers. Nevertheless, the use of such materials claims the consideration of the microbiological contamination that could lead to its degradation. Molds are known for their ability to modify locally the composition of hemp mortar by decreasing the pH level. That’s why the main objectives of the present work are, first, to expose the hemp mortar favorable conditions for mold growth, secondly, to investigate the proliferation of the mold filaments inside the hemp mortar sample and, then, to analyze the crystallographic composition. Experimentally, hemp mortar samples were exposed to high level of relative humidity during one year until the mold growth. The SEM observation allowed to follow the internal growth and identify the depth of the mold growth. Finally, the composition of the contaminated hemp mortar was studied by X-ray diffraction. The obtained results reveal that molds growth occurs not only on the surface but also in the depth. Nevertheless, as the mold growth started only after one year of high humidity exposure, a good resistance of studied hemp mortar towards molds was noted. Furthermore, the mineralogical composition analysis of the contaminated samples shows that the hydrates responsible for durability remained. These results provide data to better predict the durability of hemp mortars.