Influence of natural aging on the chemical composition of hemp mortars

In recent years, bio-based building materials have become increasingly popular in the field of low-carbon construction. Different bio-based solutions are being adopted because of their advantageous hygrothermal properties and low economic and environmental costs. One such bio-based solution is hemp mortar, which is used in France and other countries for various construction purposes, such as thermal or acoustic insulation for interior and exterior walls. However, the use of hemp mortars is hampered by insufficient data on their durability and risk of degradation due to natural environmental conditions. Indeed, hemp mortar is hygroscopic, heterogeneous and anisotropic, which makes it difficult to study its behaviour. Therefore, the main objective of this work is to investigate the effect of natural aging on the chemical composition of hemp mortar exposed outside in specially designed metal cage for two years. Experimentally, XRD and thermogravimetric analyses of hemp mortar samples were performed. All experimental results were compared with the results of reference samples treated under laboratory conditions. The effects of two different compositions and sample depths were also investigated. In general, the results showed a higher degree of degradation of the mineral matrix of hemp mortar during natural aging due to carbonation and hygrothermal stresses.