Relationship between hygrothermal and acoustical behavior of hemp and sunflower composites

• Published in: Building and environment 2021-01, Vol.188, p.107462, Article 107462
• Main Authors: Abbas, Mohamed Said, Gourdon, Emmanuel, Glé, Philippe, McGregor, Fionn, Ferroukhi, Mohammed Yacine, Fabbri, Antonin
• Format: Article
• Language: English
• Subjects: Acoustic measurement; Acoustic properties; Acoustical measurements; Bio-based materials; Building materials; Composite materials; Construction materials; Energy efficiency; Engineering Sciences; Heat conductivity; Heat transfer; Helianthus; Hemp; Hygrothermal measurements; Kundt's tube; Material properties; Moisture content; Permeability; Porosity; Porous materials; Porous media; Sunflowers; Sustainable development; Sustainable materials; Thermal conductivity; Tortuosity; Water; Water content; Water vapor
• ISSN: 0360-1323; 1873-684X
• DOI: 10.1016/j.buildenv.2020.107462

The experimental characterization of most of the hygrothermal properties of bio-based porous materials, which are characteristic for their double-scale porosity, requires for the samples to stabilize their liquid water content. Furthermore, such measurements often take several weeks to several months. In contrast, acoustical measurements can be realized very quickly by using simple and relatively inexpensive test benches such as Kundt's tube. In this article, we investigate the existence of relationships between the hygrothermal and acoustical parameters of the porous media (porosity, resistivity, tortuosity, etc.), in order to provide ways to by-pass hygrothermal measurements by performing an indirect characterization of the material properties using acoustical measurements. Two expressions have been found to properly estimate the thermal conductivity and the water vapor permeability of the studied hemp and sunflower pith composites from acoustical measurements. However, further tests will be needed in order to establish the limits of these estimations (for which materials and in which conditions are they applicable) and further research will be made to shed light on the cause of these relationships. These two properties are capital in the conception of new eco-responsible building materials since a low thermal conductivity helps to improve energy efficiency, and the water vapor permeability plays a major role on thermal inertia, moisture regulation and on comfort inside the building. With further research, these results are expected to accelerate the development of sustainable construction materials and to better consider the complex hygrothermal behavior of such materials. •Thermal conductivity depends on the inter-particle porosity of the composites.•Correlation between thermal conductivity and φinter−particle follows Lichtenecker's formula.•Air permeability and water vapor permeability are exponentially related.•Water vapor storage capacity has not been found to be related to acoustic properties.•Acoustical measurements may allow to characterize hygrothermal properties.