Performance of steel reinforcement in portland cement and high-volume fly ash concretes exposed to chloride solution

This paper describes the performance of steel reinforcement in portland cem ent. and high-volume fly ash (HVFA) concretes exposed to a chloride solutio n. A number of large slabs, 833 x 600 x 153 mm ill size, were cast from sic air-entrained concrete mixtures. Four of these mixtures were made with nor mal portland cement with the water-cement ratio (w/c) of the mixtures rangi ng from 0.32 to 0.76 the remaining two mixtures were made with the HVFA con crete with a w/(c + FA) of 0.32. The steel reinforcing bars were placed in concrete with cover thickness ranging from 13 to 76 mm. The concrete slabs were ponded with a 3.4% sodium chloride solution for a period of 6 months, and half-cell potential, linens polarization, and AC impedance techniques w ere applied to monitor the progress of the corrosion of steel reinforcement . The results indicate that the performance of the reinforcing steel bars in the HVFA concrete after 6 months of ponding with a 3.4% sodium chloride sol ution was excellent. There was no significant steel corrosion taking place on the reinforcing bars embedded in the HVFA concrete, even with IS mm conc rete cover. This performance of the HVFA concrete is equivalent to that of the control concrete with a w/ c of 0.32, and is better than the control co ncrete with w/c greater than or equal to 0.43. Significant corrosion rates were observed for the reinforcing bars embedded in control portland cement concrete with w/c greater than or equal to 0.43 . As expected, the poorest performance was of the the control concrete with a w/c of 0.76, where even the reinforcing bars with 51 mm cover exhibited corrosion.