Development optimization and performance evaluation of mineral capsules based on magnesium oxide expansive agent

Mineral capsules could improve the self-healing ability of cement-based materials by avoiding the premature reaction of minerals. This study mainly optimized the preparation process of mineral capsules and comprehensively evaluated the influence of mineral capsules on the mechanical and self-healing properties of cement-based materials. By incorporating different contents of magnesium oxide expansive agent, the basic properties of mineral capsules were investigated and the optimal dosage of healing agent was determined. The encapsulation effects of polyvinyl alcohol and epoxy resin were compared to identify the better wall material. Then the mechanical and self-healing properties of the mortar mixed with different amounts of mineral capsules were comprehensively analyzed. Results from the healing potential, granule strength and soundness of mineral cores indicated that the optimal dosage of magnesium oxide expansive agent was 60 wt%. Compared with polyvinyl alcohol, mineral capsules encapsulated with epoxy resin had higher granule strength and better alkali resistance. Although the addition of mineral capsules had a negative impact on the compressive strength of mortar, the self-healing performance was significantly improved. With increasing contents of mineral capsules, the cracked mortar obtained more pronounced crack closure and impermeability recovery.