The CO2 volume fraction for accelerated carbonation test according to Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete(GB/T 50082—2009) is 20%. However, it usually lies between 2%-5% in similar international specifications. In order to compare the impact of CO2 concentration on the test results, the concrete samples with different mineral admixtures that are widely used in many infrastructures in China were prepared and accelerated carbonation test were conducted in chambers with CO2 volume fraction being 3% and 20%. Mineral admixtures used in this investigation included fly ash, ground granulated blast furnace slag and the combination of both. The carbonation depth and carbonation rate coefficient of the concrete samples were compared. It is demonstrated that the carbonation test at 3% CO2 volume fraction follows the diffusion law of CO2 in natural environment, and the carbonation resistance of the concrete with similar water-binder ratio but different mineral admixtures can be clearly distinguished, though carbonation test takes longer time. It is found that accelerated carbonation test at 20% CO2 volume fraction fails to differentiate the carbonation resistance of the concrete with similar water-binder ratio but different mineral admixtures.%选取CO2体积分数为3％和20％进行加速碳化试验,比较分析了2种情况下单掺粉煤灰、矿粉混凝土及二者复掺混凝土碳化深度及碳化速率系数随碳化龄期的变化规律.结果表明:在3％CO2体积分数下进行加速碳化试验,不但能较好地反映普通混凝土的自然碳化规律,而且能对水胶比相同矿物掺合料不同的混凝土碳化性能进行有效区分,但试验时需要适当延长碳化龄期；采用20％CO2体积分数进行加速碳化试验,并不能有效区分水胶比相同矿物掺合料不同的混凝土的碳化性能.
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