The　mixing　process　during　concrete　manufacturing　can　solidify　CO2,　which　can　facilitate　CO2　utilization　and　reduce　the　carbon　emissions　of　the　cement　industry.　However,　excessive　CO2　intervention　(＞0.3　wt%)　during　mixing　can　decrease　the　ease　of　use　and　deteriorate　the　mechanical　properties　of　concrete,　thereby　reducing　its　serviceability.　In　this　study,　CO2　was　added　in　the　mixing　stage　at　a　certain　mass　ratio　relative　to　cement　(0.5-2.0　wt%).　To　elucidate　the　strengthening　effect　of　CO2,　the　factors　contributing　to　the　deterioration　of　the　cement　properties　induced　by　CO2　and　coupling　of　the　carbonation　and　hydration　mechanisms　were　investigated　using　mechanical　tests,　ion　concentration　analysis,　scanning　electron　microscopy,　X-ray　diffraction　analysis,　mercury　intrusion　porosimetry,　and　other　testing　methods.　CO2　stimulated　the　rapid　hydration　of　clinker　minerals　to　form　a　C-S-H　gel,　which　rapidly　set　the　slurry　and　deteriorated　its　fluidity　and　mechanical　properties.　Such　rapid　setting　was　no　longer　observed　after　coupling　the　carbonation　and　hydration　mechanisms.　CO2　caused　calcovanadite　to　form　hexagonal　prisms　with　high　degrees　of　crystallization　and　optimized　the　combination　of　calcovanadite　with　other　hydration　products.　CO2　also　refined　the　pore　structure　of　the　slurry　to　enhance　the　compressive　strengths　after　3,　7,　and　28　d　by　36.5　%,　24.8　%,　and　20.0　%,　respectively,　with　a　CO2　dosage　of　1.6　wt%,　which　considers　the　degree　of　carbon　sequestration　and　performance.　Thus,　this　study　provides　a　theoretical　guide　for　CO2　application　in　cement-based　materials.