Corrosion Behaviours of Steel Embedded in fly Ash Blended Cements

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Title: Corrosion Behaviours of Steel Embedded in fly Ash Blended Cements

Author(s): H. T. Cao, L. Bucea, B. Wortley, and V. Sirivivatnanon

Publication: Special Publication

Volume: 145

Issue:

Appears on pages(s): 215-228

Keywords: carbonation; cement pastes; chlorides; corrosion; curing; fly ash; mortars (material); pozzolanic reactions; reinforcing steels; Materials Research

Date: 5/1/1994

Abstract:
Corrosion characteristics of steel embedded in hardened cement pastes and mortars were investigated by using data obtained from potentiodynamic anodic polarization and polarization resistance techniques. One normal portland cement and one fly ash were used. The dosages of fly ash as cement replacement material were 0, 20, 40, and 60 percent. The results indicate that there was no negative effect of pozzolanic reaction of fly ash on steel passivation, even at a high replacement dosage of 60 percent, and after 2 years of curing. In fact, with prolonged curing, steel embedded in fly ash-blended cement pastes was found to have a higher degree of passivation with greater stability than that embedded in plain cement paste. Chloride binding capacity of 40 percent fly ash-blended cement paste, as indicated by the measured corrosion rate of steel, was found to be very effective after 3 days of curing. In accelerated carbonation condition, corrosion rates of steel were initially high in fly ash-blended cement mortars. When fully carbonated, the results indicate that the corrosion rate of steel can be higher in plain cement in comparison to 40 percent fly ash blend. In the case of chloride penetration, the corrosion rate of steel was found to be consistently less than that of equivalent plain cement when compared on an equal water-binder ratio.