Assessment of the durability of bio-based insulating materials

Résumé : The use of vegetal concretes, such as hemp concrete, is growing for building insulation. They are constituted by vegetal aggregates embedded in a mineral binder. Hemp concretes are multifunctional materials: they have good thermal and acoustical insulating properties and their hygrothermal behavior enables a natural moisture regulation. Unfortunately, the use of hemp concrete is limited by its lack of guarantees in terms of durability. This paper focuses on the study of the evolution of the properties of hemp concretes after accelerated ageing in laboratory. The samples are submitted to wetting/drying cycles and their performances are analyzed periodically. In this article, the properties of the materials after 75 days of ageing are reported. It is shown that this period is too short to observe any significant variation of the properties of the hemp concretes, except for their porosity. The biological ageing of the materials is investigated too. It is shown that the mold growth occurs when the relative humidity is high (98% RH) and when the pH of the binder has decreased due to its carbonation reaction.