Influence of liquid water on thermal and acoustical properties of hemp concretes

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 influence of liquid water on thermal and acoustical properties of hemp concretes. It is shown that wetting and drying cycles do not appear to degrade the properties of the material. Moreover, the water added to the surface of hemp concrete does not saturate the surface layer before penetrating more deeply into the material. Nevertheless, when a large amount of water is added, the acoustical behavior of hemp concrete becomes analogous to that of a two-layer material insofar as most of the acoustic energy is reflected by the first layer of hemp concrete, which is completely wet. Finally, the thermal conductivity of the material seems to stabilize from a certain volume of added water.