Due to various reasons, such as insufficient compaction, early drying, etc., the quality of surface concrete is usually lower than that of inner concrete made of the same initial concrete. Unfortunately, durability of reinforced concrete in terms of the corrosion of reinforcing bars is largely governed by the resistance of this surface concrete against the ingress of harmful substances. As an indicator for that resistance, air permeability of surface concrete is controlled by not only the initial mix proportion, but also the curing condition and duration. This research was to experimentally investigate the effect of curing conditions on the air permeability of surface layers of different concretes. Concrete cylinder specimens made of different mix proportions were exposed to dry condition up to 56-age day after different initial curing conditions and durations. Air permeability was measured using the non-destructive double-chamber method developed by Torrent. Experimental results indicate that curing condition greatly affects the air permeability of the cover concrete: The longer the initial sealed or in-water curing period, the lower is the air permeability of cover concrete. This research confirmed that air permeability may be used as an indicator for potential durability of concrete cured under different curing conditions and durations.
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