Coupled effect of self-healing granules and permeable crystalline additive on early-age cracks repair in cement material

Cement-based materials are prone to cracks that affect their strength and durability. The service life of these materials can be extended through development of self-healing cement-based materials. This study indepen-dently designed and produced self-healing granules and explored the synergistic effects of using self-healing granules and permeable crystalline additive. The self-healing efficiency is evaluated via crack closure and the compressive strength recovery rate. The porosity and crack healing products were analyzed to discuss the self-healing mechanisms, revealing that the reaction of the granule inner core with cement precipitates can heal the cracks up to approximately 1 mm after the self-healing granules are ruptured, and permeable crystalline additives can greatly increase the compressive strength recovery rate by closing the microcracks/pores. Self-healing granules and permeable crystalline additives allow for the repair of microcracks and visible cracks in specimens, realizing self-healing at the macro-and micro-scale. These results provide promising self-healing cement-based materials and a novel research direction.