Effect of water content on the acoustical and thermal properties of hemp concretes

Hemp concrete is a multifunctional ecological material used in buildings. It is obtained by mixing a binder with hemp particles (the non-fibrous fraction of the hemp stem called “shiv” or “hurd”). Due to its high porosity (ranging from 60 to 90%), it presents an “atypical” mechanical behavior and its hygrothermal and acoustical properties are particularly interesting. This paper focuses on the influence of the water content of hemp concretes on their acoustical and thermal properties. Four mixtures of hemp concrete were manufactured using a binder and two shives under two distinct stresses of compaction. It is shown that water content does not affect significantly the acoustical properties of hemp concretes although a swelling effect can be detected by an increase of resistivity and a decrease of porosity. Finally, this study confirms that thermal conductivity rises almost linearly with water content while evolutions of thermal diffusivity and specific heat capacity are different depending on the concrete.