Characterization of a hemp-based agro-material: Influence of starch ratio and hemp shive size on physical, mechanical, and hygrothermal properties

Hemp shives is a lightweight material known for its insulating properties. Associating these bio-fibers with plant-based matrix instead of a mineral binder in insulation applications is of ecological interest. This article describes the study of a low environmental impact 100% plant-based material made solely from wheat starch and hemp shives. The hemp/starch ratio (H/S) influence and hemp shive size are studied. Samples are evaluated in terms of physical properties, mechanical behaviour and hygrothermal properties through an experimental approach. Results show that increasing 0-5 mm hemp shive proportion from 15% to 30% leads to a significant enhancement of the mechanical and hygric characteristics due to the load transfer and porosity. However, when the H/S ratio increases, mechanical and hygrothermal characteristics decrease slightly. Finally, the hemp-starch agro-material with H/S equal to 8 and 30% of 0-5 mm hemp shive seems to be the optimal composition between the studied samples.