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

Plant aggregates and fibers in earth construction materials: A review

International audienceEarth as a building material is increasingly being studied for its low environmental impact and its availability. Plant aggregates and fibers have been incorporated into the earth matrix in the aim of enhancing performance for thousands of years but scientific studies began quite recently. The present paper reviews the state of the art of research on the influence of these various natural and renewable resources in unfired earth materials such as compressed earth blocks, plasters, and extruded and stabilized blocks. This review, based on 50 major studies, includes characterization of the particles and treatments, and recapitulative tables of the material compositions, and the physical, mechanical, hygrothermal and durability performances of earth-based materials. A lack of references on hygroscopic and durability properties was observed. Future research orientations are thus suggested to promote and develop this type of sustainable material, which provides a solution for saving energy and natural resources. Highlights Earth-based products with plant aggregates as a sustainable material are reviewed. Physicochemical and mechanical properties of plant aggregates or fibers are reviewed. Mechanical, hygrothermal and durability performances of the composites are reviewed. Further investigations are needed to promote these materials

Effect of Plant Aggregates on Mechanical Properties of Earth Bricks

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Comparative study between natural and PVA fibers to reduce plastic shrinkage cracking in cement-based composite

WOS:000356118300023International audienceThe main objective of this study is to control restrained plastic shrinkage cracking through the addition of natural and PVA fibers in a cement-based composite. Two types of natural fibers (flax and agave lechuguilla) as well as synthetic fibers (PVA) were investigated at volume fractions of 0.1% and 0.7%. 38 prismatic mortar specimens were freshly cast on top of a grooved and hard concrete substrate, providing a bottom restraint; this resulted in cracking in the freshly placed overlay, which was detected as a function of time. The effectiveness of the fibers was evaluated by considering reducing the number of cracks and total crack area under these conditions. The results obtained show that both natural fibers were effective in controlling restrained plastic shrinkage cracking like the commercially available PVA fibers; the total crack areas were also reduced by at least 93% compared with plain mortar specimens. (C) 2015 Elsevier Ltd. All rights reserved