A recycling process of waste cement by carbonation reaction with pressurized CO2 is discussed. It is found that the proposed process consists of two main reactions. The first is the extraction of calcium ions from waste cement particles in water slurry by pressurized carbon dioxide. The second is the precipitation of calcium carbonate (CaCO3) by reducing the pressure of CO2. The product, CaCO3 can be recycled as a raw material for cement production. The results show that the extraction process can be proceeded with relatively high rates in the initial 10 minutes of the reaction time, where the concentration of calcium ions exceeded thermodynamic solubility.