Abstract
The impact of building materials on the environment and the health of occupants is nowadays a priority issue. Ecological construction materials such as earthen materials are currently experiencing a regain of interest due to both ecological and economic factors. The microbial proliferation on indoor materials can induce a deterioration of the building air quality and lead to an increase of health risks for the occupants. The issue of indoor air quality raises questions about the use of earthen building materials and their possible susceptibility to fungal development. The microflora of earthen materials and their ability to grow on such support are indeed poorly studied. This study focused on the quantification of both bacterial and fungal microflora along the manufacturing process. The impact of extreme humidity, simulating a hydric accident, on microflora development was analyzed on the surface and inside earthen bricks. The initial microflora of these materials was dramatically reduced during the manufacturing process, especially after heat treatment for drying. Proliferation of remaining microorganisms was only observed under high humidity condition, in particular for earthen materials with vegetal aggregates. Moreover, in situ samplings were performed on naturally dried earthen materials used in buildings. The characterization of the microbial density revealed a higher microbial density than on manufactured specimens, while microbial concentration and detected taxa seemed mainly related to the room use and building history. These results provide a better understanding of microbial proliferation on these materials.
Highlights
Current ecological concerns are leading us to give greater consideration to the environmental impact of building materials
Samples were taken during the manufacturing process in order to assess the initial presence of microorganisms in the manufactured earthen materials studied
The addition of plant fibers led to the detection of a greater number of microorganisms than found on the surface of the earth‐only specimens, even with only 3% of straw
Summary
Current ecological concerns are leading us to give greater consideration to the environmental impact of building materials. Earthen materials are part of the several environmentally friendly materials used to address these ecological challenges. Earthen building materials have a variety of interesting characteristics, such as their capacity to induce natural regulation of the indoor air humidity [1], their reduced environmental impact [2] and their low cost [3]. The addition of vegetal aggregates (straw, hemp, etc.) within earthen materials induces an improvement in their thermal insulation as well as a reduction of shrinkage cracks when the materials dry out after manufacturing [4]. The addition of compounds containing cellulose and/or lignin may, promote microbial growth [5]. Microbial proliferation in buildings has become a major challenge in recent decades
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