Carbonation of solid calcium oxide by gaseous carbon dioxide was monitored by thermogravimetry. A kinetic model of CaO carbonation is proposed in order to interpret the first rapid step of the reaction. By taking into account, the existence of large induction period as well as the sigmoidal shape of the kinetic curves in this kinetic-controlled region, a surface nucleation and isotropic growth kinetic model based on a single nucleus per particle is proposed, and the expressions of the fractional conversion and the reaction rate versus time are detailed. The induction period is found to have a linear variation with respect to temperature and to follow a power law with respect to CO₂ partial pressure. The areic reactivity of growth decreases with temperature increase, and increases with CO₂ partial pressure increase. A mechanism of CaCO₃ growth is proposed to account for these results and to determine a dependence of the areic reactivity of growth on the temperature and the CO₂ partial pressure.