Assessing the bond strength of expansive agent-enhanced repair mortars for ageing concrete structures

As reinforced concrete structures age, they increasingly require extensive maintenance and repair. Due to their limited lifespan, repair materials are often susceptible to early cracking, resulting from environmental influences, deformation, and physical-chemical incompatibilities between the repair material and the substrate. In line with sustainable development goals, minimising costly maintenance and repairs is essential. Self-healing mortar presents a promising solution to extend the durability of repaired structures and reduce long-term maintenance needs. The primary objective of this research is to evaluate the self- healing capacity of a cementitious material containing magnesium oxide and calcium sulfo-aluminate-based expansive agents, as well as to assess its mechanical performance under repair conditions. Healing kinetics are monitored through water permeability tests on cylindrical specimens precracked at 28 days. To validate the suitability of the studied mortars for repair applications, their bond strength is measured using pull-off tests under various concrete substrate conditions, including different roughness and saturation levels. Experimental results indicate that incorporating an expansive agent enhances the autonomous healing potential of mortars, with mortars containing calcium sulfo-aluminate-based expansive agents demonstrating superior bond strength and a better healing capacity.