Effect of compaction on thermal and hygric properties of hemp composites

Abstract

This study is part of the European ISOBIO project which aims to develop new bio-based building materials, through the valuation of agro-resources as bio-based aggregates or as green binders. Previous studies investigated several types of aggregates and binders. They highlighted that the main impacting factor on thermal conductivity was the density of composite. The aim of this paper is to investigate the effect of density on hygric and thermal properties of composites, using the same formulation. The composites are made of hemp shiv and black liquor. Specimens are produced with the same hemp to black liquor ratio but different compaction stress. The effect of compaction on bulk density, thermal conductivity and moisture buffer value (MBV) is analyzed. More it is shown that it is possible to reach low enough thermal conductivity to be considered as building insulating material, regarding the AFNOR NF 75-101 French standard [AFNOR 1983]. Thanks to this study, target density, and thus compaction stress to be applied, can be identified regarding thermal conductivity and MBV.