Disclosed are a crack self-healing agent for cement-based materials capable of binding corrosive ions in seawater, and a preparation method thereof. A core material of the agent is an active inorganic composite component capable of chemically binding Cl, Mg, and S, a wall layer is polymethyl methacrylate, and an interface improvement layer is a cement layer. A preparation method includes: (1) thoroughly mixing active components capable of binding corrosive ions, and filling a resulting mixture into a direct compression mold; (2) applying a pressure to the direct compression mold and holding the pressure on using a pressing machine, and demolding to obtain a core material body; (3) placing the core material body obtained in a solution of PMMA in acetone for coating, and taking out the core material body and drying; (4) coating a layer of cement before the acetone is completely volatilized to obtain the crack self-healing agent.

The present invention relates to the manufacture and use of off-specification fly ash (OSFA), which would have otherwise been landfilled, in preparing ultra-high-performance concrete (UHPC). The present invention aims to provide a new avenue for valorization of OSFA in the concrete industry by utilizing high-volume OSFA in producing UHPC. Compared with conventional concrete and high-performance concrete, UHPC is a family of advanced concrete featuring exceptional compressive strength, ductility, and long-term durability. Application in UHPC is expected to be a new and feasible technology to efficiently recycle OSFA.