Experimental investigation on the performance of hybrid hempflax composite materials

Abstract

An experimental investigation was conducted in order to study the water absorption, mechanical performance and drying shrinkage of hybrid hemp-flax composite materials. The hemp-flax composite material is made with 90% hemp shives and 10% flax fibres. Hemp aggregates have a high capacity for water absorption, which led to a reduction of the mechanical performances of hemp concretes. The purpose of this study is to investigate the influence of the incorporation of short flax fibres in hemp concrete. Four mixes were made for: shuttered walls, external rendering, floor insulation and roof insulation. In first stage, the water absorption of flax and hemp shives was measured. The compressive strengths of these mixes were then determined to compare the mechanical behaviour of the hybrid composite material with hemp concrete and the capillary absorption of these bio-based materials were also measured. The endogenous shrinkage of these materials was also measured. Finally, we measured the coefficient of thermal conductivity of these materials. The results of the compressive strength show a significant improvement due to the hemp-binder ratio. The incorporation of the flax fibres in hemp concrete also led to an increase of the compressive strength for large strains (above 5%). It was observed that the capillary absorption of hybrid composite was decreased when a high content of binder was used. Finally, flax fibres have reduced hempcrete shrinkage of about 15%.