Moisture transfer and thermal properties of hemp–lime concretes

Abstract

Lime–hemp concrete is a low-embodied energy, carbon-negative, sustainable construction material made with a lime-based binder and hemp aggregate. This work investigates moisture and thermal properties of hemp concretes made with hydrated lime and pozzolans, and those including hydraulic lime and cement. The paper concludes that the type of binder influences capillary action of hemp concrete and that increasing the hydraulicity of the binder, as well as adding a water retainer, reduces capillary absorption. The impact of the binder type on permeability is less evident, and the results indicate that the large interparticular spaces between hemp particles (macropores) contribute to permeability to a greater extent than micropores (which are influenced by the hydraulicity of the binder).Finally, the binder type did not have a statistically significant impact on either thermal conductivity or specific heat capacity. A trend however suggests that increasing the binder’s hydraulic content reduces thermal conductivity and increases heat capacity; and that the presence of water retainers enhances both conductivity and heat capacity.