Chemical mechanisms governing the evolution of functional properties of nonwoven hemp geotextiles aged under two soil environmental conditions

This study investigates the chemical mechanisms governing the ageing of nonwoven hemp geotextiles in alkaline recycled concrete aggregate soils (pH ≈ 10.5) under water saturated and unsaturated conditions over six months, using XRD, FTIR and biochemical analyses. Under water saturated conditions, crystallinity of hemp remains stable despite compositional changes consistent with preferential removal of non-cellulosic constituents and possible alkaline-induced perturbation of cellulose organisation. In contrast, unsaturated conditions lead to increased apparent crystallinity and more severe degradation, consistent with preferential removal of amorphous constituents and enhanced biological activity. Because microbial biomass was not directly quantified and no absolute mass balance was established, its possible contribution to the apparent stability of bulk carbohydrate composition is considered a hypothesis rather than a demonstrated mechanism. Overall, degradation pathways differ depending on hydric conditions, with direct implications for geotextile durability in road environments.