Effect of hemp fibers and crystalline admixtures on the properties and self-healing efficiency of lime and clay-based mortars

This study investigates the impact of hemp fibers on two fiber-reinforced compositions, claybased and lime-pozzolan mortar. Three compositions were prepared for each mortar, reference samples without fiber incorporation, samples with untreated hemp fibers, and samples with hydrothermally treated hemp fibers with crystallines. Crystalline admixtures (CAs) were incorporated into the hydrothermal pretreatment of fibers to promote the self-healing properties of the mortar when needed. Physico-mechanical and thermal properties took place to address the overall effect of hemp on the mortars. Adding hemp fibers enhanced the mechanical strength and reduced the mortars' shrinkage. The hydrothermally treated fibers have better cohesion with mortars, preserving the best results. To evaluate self-healing efficiency, pre-damaged cubic samples from each composition were subjected to tap water immersion for lime-pozzolan mortars and a controlled humid chamber for clay mortars after a curing period. The healing rate was assessed by measuring crack closure, compressive strength recovery, and the dynamic modulus of elasticity recovery. The results indicated significant strength recovery in lime-pozzolan mortars with hemp fibers. Clay-based mortars showed moderate strength increases and limited selfhealing.