Many types of accelerated tests for carbonation have been undertaken in order to investigate the carbonation process of concrete. In this study, we chose the following as the factors which would have an influence on the results of accelerated carbonation tests for concrete : the dimensions of the specimen, the pre-curing conditions and the accelerated conditions. The test results are summarized as follows. (1) The relation between time and carbonation depth varied with the test conditions. Carbonation depth was proportional to the power of time (b) which was a little less than 0.5 on average, but the value can be considered to be 0.5 for practical circumstances. (2) The carbonation rate reduces with the increase of the dimensions of specimen. (3) The carbonation rate of seal-cured concrete is a little higher than that of concrete cured in water. (4) The carbonation rate of concrete cured for 7 days is nearly equal to that of concrete cured for 28 days, but that cured for 3 days becomes about 20 % higher than that cured for 28 days. (5) The carbonation rate of concrete increases with the increase of 'the period of drying before the accelerated carbonation tests. (6) The carbonation rate increases with the increase of temperature. (7) It is supposed that there is a pessimum condition of carbonation rate near 40 % humidity. (8) The carbonation rate was proportional to the power of density of carbon dioxide which was a little less than 0.5 on average, but the value can be considered to be 0.5 for practical circumstances.
