This Paper reports an experimental investigation to establish the influence of ambient CO2, concentration, exposure temperature and curing duration on the rate of carbonation in concrete. The test specimens were concrete cylinders 100 mm in diameter and 200 mm high. Of the parameters investigated, the standard 28-day compressive strength f28 was found to be effectively representative of the concrete quality in several carbonation models proposed. Index test results, i.e. water absorption and sorptivity, were also incorporated to depict the effects of the surface property of concrete. The proposed models agreed well with the experimental data.