A novel bio-inspired bone-mimic self-healing cement paste based on hydroxyapatite formation

Abstract A novel bone-mimic self-healing cementitious material was developed by mimicking the healing process of bionic bone fracture using hydrogel impregnated with phosphate in Portland cement paste. The properties of phosphate-incorporated hydrogel, feasibility of hydroxyapatite formation in pore solution, release of phosphate from the hydrogel into cement paste, phase assemblage of self-healing products in the crack of cement paste and the self-healing efficiency were investigated with a range of analytical techniques. The phosphate-incorporated hydrogel can release phosphate into cracks at controlled rate. Carbonated and calcium deficient hydroxyapatite particles with sizes of approximately 30 μm were found as the main phase assemblage in the cracks during the self-healing process. The healing products grew from the surface of both sides to the center of crack. The compressive strength and impermeability of the self-healing cement pastes containing hydrogel impregnated with phosphates were fully restored after being cured for 28 days. The autonomous self-healing by introducing phosphate in hydrogel contributed the most to healing capacity, followed by the autogenous self-healing driven by the water released from hydrogel and the autogenous self-healing of cement paste. The hydroxyapatite-type products intermixed with minor amounts of calcite formed in the cracks accompanying the controlled release of phosphate from the hydrogel, providing the self-healing capabilities of the cement paste.