Impact of the water content of hemp concretes on their thermal and acoustical properties

Abstract

Hemp concrete is a multifunctional ecological material used in buildings which is obtained by mixing together a binder and hemp particles (the non-fibrous fraction of the hemp stem called “shiv” or “hurd”). Due to its high porosity (ranging from 60 to 90% in volume), it presents an “atypical” mechanical behavior and its hygrothermal and acoustical properties are particularly interesting. This paper focuses on the impact 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 altough a swelling effect can be detected by an increase of resistivity and a decrease of porosity and viscous characteristic length. Finally, thermal conductivity rises almost linearly with water content while evolutions of thermal diffusivity and specific heat capacity are different depending on the concrete.