Development of bio-based earth products for healthy and sustainable buildings: Characterization of microbiological, mechanical and hygrothermal properties

The impacts of buildings on the environment and on the health of the inhabitants are priority issues nowadays. For many environmental, social and economic reasons, the demand for building products made of materials such as earth and bio-based materials is increasing. Under certain conditions, mold growth can be observed on the surface of such materials, which raises many questions about their use in buildings. In the framework of the "BIOTERRA" ANR project, the aim of the study was to develop and characterize an earth based material incorporating plant fibers from both abiotic and biotic points of view. Compressive strength, thermal conductivity and water vapor permeability of this material were determined. Microorganism sampling methods intended for raw materials and cylindrical specimens were optimized, and the microflora profile of these materials was then obtained. The results showed that the straw addition led to a decrease of compressive strength and an increase of thermal insulation. However, it did not influence water vapor permeability coefficient. Raw materials and manufactured specimens contained mainly Bacillus sp., Aspergillus sp. and Penicillium sp. Other compositions of this bio-based material will be characterized. Sampling methods developing here can also be used to identify the microflora of existing earthen buildings.