Quantification of Hemp Concrete Displacement Subjected to Hygrothermal Solicitations Based on 2D DIC

Integrating plant aggregate into building envelope insulation materials, such as hemp concrete, provides a promising approach to reducing the energy consumption and carbon footprint of buildings due to its excellent hygrothermal performances and low carbon footprint. Considered a highly hygroscopic material, hemp concrete exhibits susceptibility to hygrothermal solicitation. This characteristic causes dimensional variations (swelling/shrinkage) and consequently leads to damage in the material cracking especially at the interface zone. In addition, this material is highly heterogeneous and therefore requires better consideration of its behavior on a finer scale. The present study aims to improve the precise understanding of how temperature changes impact the morphological variations of hemp concrete. For this purpose, a specialized mini climatic chamber equipped with telecentric lenses, ultra-resolution cameras, and a precise temperature and humidity controller was designed to acquire a high-quality image of hemp concrete under heating-cooling cycles (15°C-50°C-15°C) with the constant relative humidity state. Next, the strain of the hemp concrete was visualized and quantified based on the 2D digital image correlation (DIC) technique. Particular attention was also devoted to the strain uncertainty. The results show that DIC is an accurate method for determining the local deformation characteristics (aggregate and interface) of hemp concrete. The acquired swelling/shrinkage percentage in hemp aggregate and interface zone inside hemp concrete could serve as input for numerical modeling of coupled hygro-thermal properties in the material.