Pulverized-fuel ash concrete: Carbonation-induced reinforcement corrosion rates

An investigation of the effect of pulverized-fuel ash on carbonation-induced corrosion of reinforced concrete is presented. A wide range of concrete parameters has been considered, including cement content, workability, strength grade and curing. Corrosion activity has been assessed non-destructively, using the half-cell potential and polarization resistance test methods. Destructive tests using gravimetric weight loss have been used to confirm these measurements at the conclusion of the tests. Carbonation of the specimens was accelerated using a specially designed apparatus. These specimens were then exposed to a range of post-carbonation exposure environments where the ambient relative humidity was varied. The results suggest that the normally considered factors controlling concrete durability, which are relevant for the time delay to the onset of corrosion, do not apply to the rate of attack once corrosion actually starts, and a series of possibilities are therefore proposed, which may be used to explain the observed phenomena.