Hygrothermal behavior at the junction of cement mortar and biobased materials: Finite element study of hempcrete, date palm concrete, and clay brick

This study investigates the hygrothermal behavior at the junction between cement mortar and three biobased materials, hempcrete, date palm concrete, and clay brick, using the finite element method. Numerical simulations were conducted under both summer and winter conditions to analyze temperature and relative humidity distributions across a multilayer block at a depth of 145 mm. The results reveal that each material exhibits a distinct hygrothermal signature. Hempcrete ensures stable moisture buffering and smooth gradient transitions. Date palm concrete offers high moisture transfer and insulation performance, but with sharper discontinuities. Clay brick shows intermediate behavior with moderate buffering and more gradual junction transitions. The finite element method results highlight the junction as a critical zone where mismatches in material properties can lead to moisture accumulation, mechanical stresses, and durability concerns. These findings underscore the importance of selecting compatible materials and designing junctions carefully to ensure long-term performance and comfort in biobased building envelopes.