Variation of carbonation resistance of ordinary concrete containing slag with moist-curing time at early ages

Based on accelerated carbonation test, the variation of carbonation resistance of ordinary concrete (C30 grade) with moist-curing time at early ages and slag content was studied in this paper. Results indicate that the carbonation resistance of the concrete decreased obviously with moist-curing time at early ages reducing and with the cement replacement by slag increasing. For example, under conditions of curing schedules with 28, 7, 3, 2 and 1 d moist-curing at early ages and then 0, 21, 25, 26 and 27 d air-curing at (60±5)% RH respectively, the 28-day accelerated carbonation depths of the concrete incorporated with 30% slag were 12.3, 17.0, 22.2, 27.9 and 42.1 mm respectively, and thus it can be seen the calculated times when concrete cover (25 mm) was completely carbonated naturally in the air were 158, 83, 49, 31 and 14 years respectively. The results suggest that for the carbonation resistance of the concrete incorporated with 15%~30% slag, it is necessary that the moist-curing time at early ages should need 7 days.