Nanolime dispersions as active agents in self-healing lime mortars for durable heritage preservation

Built heritage is facing growing exposure to diverse and severe risks as the impacts of climate change intensify. To address these challenges, historic masonry repair techniques must evolve to support more resilient and durable preservation strategies. In this context, recent advances in self-healing concrete technologies offer promising pathways to adapt and transfer these approaches to heritage conservation, particularly for lime-based materials used in historic masonry. This study investigates the potential of nanolime dispersions as self-healing agents for natural hydraulic lime (NHL) mortars, applied through vascular network systems specifically designed to be fully integrated within mortar joints while ensuring chemo-physical and mechanical compatibility with the host material. Two water–ethanol formulations (50:50 and 80:20 ratios) were evaluated for their impact on mechanical performance and physicochemical compatibility with NHL matrices. Healing efficacy and compatibility were examined using three-point bending tests, FT-IR, XRD, and SEM analyses. Although no autogenous healing was observed, the nanolime treatments achieved up to 12% strength recovery, while stiffness recovery remained negligible. Notably, this nanolime-induced healing effect persisted for up to 280 days, highlighting its long-term potential. FT-IR and XRD results indicated possible formation of C-S-H phases, and SEM imaging confirmed morphological compatibility with the NHL matrix. Overall, the findings support the application of nanolime dispersions as a viable agent of self-healing strategies for the durable and compatible repair of lime-based heritage mortars.