ABSTRACT
Figure II shows a (35 n/mm2 w/c ratio 0.35) concrete prism cast with deliberately variable cover over the reinforcing bar which was cleaned prior to casting. After three year’s exposure in a mild rural environment of very low relative humidity, the concrete prism was cut open and sprayed with phenolphthalein indicator to determine the variation in carbonation. The small, apparently insignificant crack just visible on the lower middle of the block has clearly contributed towards depassivation around the reinforcing steel locally.
