Porous structure and water vapour sorption of hemp-based materials

Abstract

This paper deals with environmentally friendly building materials: lime–hemp render, hemp mortar and hemp wool. The investigations are based on porous structure and water vapour sorption studies that provide both hygric property and fruitful data on the porosity of materials. The pore size distribution is measured by mercury porosimetry and is computed from water vapour sorption with BJH model. The results show that lime–hemp render and hemp mortar include mainly macropores, and also mesopores and micropores. This result is in line with the water vapour sorption isotherms measured classified as type II. The specific surface areas are computed from mercury porosimetry and from water vapour sorption measures with BET, t and BJH methods. The values obtained with mercury porosimetry under-evaluate those calculated with other methods that are similar to each other. Lastly, with a hypothesis of fractal geometry, a fractal dimension is evaluated from water vapour sorption isotherms.