Crack repair in cement-based materials via microencapsulation of healing agents in fine lightweight aggregates

Cementitious materials are the most widely utilized construction material globally, but their susceptibility to cracking significantly compromises the durability and service life of infrastructure. Conventional repair strategies are costly, labour-intensive, and environmentally unsustainable, creating the need for innovative approaches that enhance resilience while reducing the sector’s carbon footprint. Autonomous self-healing cementitious materials are a transformative solution that enables in-situ crack repair, resulting in extended service life, minimized cementitious waste, and lower embodied carbon emissions. This study investigates a microencapsulation-based self-healing approach using fine lightweight aggregates impregnated with healing agents and coated with protective shell materials. The use of sub-1.18 mm aggregates was chosen to preserve compressive strength while simultaneously serving as carriers of the encapsulated agents. Two inorganic materials, sodium silicate and calcium chloride are used as the healing agent and incorporated as core materials, while epoxy resin and polyurethane were applied as shell components to ensure encapsulation stability and fracture-triggered release. Mortar specimens incorporating different combinations of healing agents and shell systems were fabricated and benchmarked against control mixtures without healing functionality. After 28 days of curing, specimens were pre-cracked to simulate microcrack formation. Healing performance was quantitatively assessed over a subsequent 28-day period using image analysis. Results from this study demonstrate that the impregnated lightweight aggregates achieved up to 78% crack closure efficiency, which confirms their potential to significantly mitigate crack propagation and restore microstructural integrity. The findings from this study also present a viable pathway for integrating healing agents within fine lightweight aggregates to achieve autonomous crack repair in cementitious materials. • Self-healing mortar developed using impregnated lightweight aggregates. • Sodium silicate enabled gel-type healing with up to 66% efficiency. • Calcium chloride produced crystalline sealing, enhancing durability. • Encapsulation shells controlled release, epoxy outperformed polyurethane. • CCE system showed the highest healing efficiency at 78% after 28 days.