Influence of Fly Ash and Slag on Combined Alkali-Silica Reaction and Corrosion of Steel in RC Structures

Supplementary cementitious materials (SCMs) utilized to attenuate steel corrosion or alkali-silica reaction (ASR) damage in concrete have not yet been investigated in the context of the combined action of the deterioration processes. This research examines the impact of fly ash and slag on the combined effect of steel corrosion and ASR on concrete structures. Concrete beams having fine aggregate susceptible to ASR (reactive) and fine aggregate not susceptible to ASR (non-reactive) with 20 mm concrete cover utilizing 100% PC, 50/50 PC/SL, and 70/30 PC/FA binders with a constant w/b ratio of 0.60. After 7 days of water curing and 20 days of air curing, beam specimens were exposed to three-cycle conditions for one week each; the beams were exposed to high humidity of 94 ± 3% in a storage tank at 38 ± 2 °C, wetting (with 5% NaCl) and air-drying cycles in the laboratory for 52 weeks. The specimens were monitored for expansion and corrosion evaluation tests at the completion of each humid exposure and wetting cycle. The results indicate that slag and fly ash in structures containing reactive aggregate exposed to chloride (combined effect) resulted in a higher rate of expansion and corrosion than specimens with non-reactive aggregate (aggregate not susceptible to ASR). Moreover, the 100% PC specimens with reactive aggregate exhibited a higher corrosion rate and expansion than the SCM specimens with reactive aggregate.