Carbonated steel slag aggregate and preparation method thereof

The invention discloses a carbonated steel slag aggregate and a preparation method thereof. The method comprises the following steps: sieving steel slag subjected to iron separation, taking particles with size between 0.5-25 mm particle for high pressure water flushing, and naturally drying the particles; immersing the dried steel slag particles in a mixed solution of 20-300 g/L caustic soda and 60-300 g/L sodium carbonate for 24 h, and maintaining the temperature at 20-60 DEG C; draining the soaked steel slag particles, immediately placing the particles in a sealed carbonation reactor, and introducing CO2 gas with purity over 99.9% for curing at the temperature of 70-90 DEG C for 0.5 h, and with the CO2 gas pressure at 0.2-0.5 MPa; cooling the steel slag particles subjected to carbonation treatment under natural conditions to room temperature, so as to obtain the carbonated steel slag aggregate. The steel slag aggregate treated by the method has compact surface structure to reduce water for concrete mixing; free magnesium oxide and free calcium oxide are conversed into carbonate precipitation to eliminate the hidden trouble of adverse stability; CO2 can be stored stably; the amount of natural aggregate is reduced to save nonrenewable resources; and the method has easily available raw materials and simple process.