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This study concerns the corrosion behavior of steel in different room temperature cured alkali-activated fly ash mortars exposed to chloride solution. The corrosion process was monitored by polarization resistance and corrosion potential measurements and the results were interpreted in the light of a complete microstructural, mechanical and chemical characterization of the mortars. The most compact alkali-activated mortars have higher porosity and lower mechanical properties than a cement-based mortar (CEM), but the protectiveness afforded to the rebars is slightly higher than that obtained in CEM. The reason for this discrepancy is connected to a lower chloride content accumulated in the former mortar type and to a specific inhibition of the rebar corrosion afforded by the pore electrolyte in alkali-activated mortars

This research investigates the corrosion protection afforded to the embedded rebars by room temperature-cured alkali-activated mortars, based on class F fly ash (FA), during wet and dry (w/d) exposures to 0.1 M NaCl solution. The results were compared to those obtained in a traditional cement-based mortar (REF). The rebar corrosion behaviour was characterized by corrosion potentials (Ecor) and potentiostatic polarization resistance (Rp) measurements, polarization curve recording and Electrochemical Impedance Spectroscopy (EIS). The information collected suggested that FA mortars afforded a lower corrosion protection to the rebars and the reason was investigated by microstructural, physical-mechanical and chemical analyses of the mortars. FA mortars were found to undergo a fast carbonation, so that depassivation of the rebars occurred concurrently, in spite of a limited total chloride content inside these mortars. REF mortar was much less susceptible to carbonation and rebar corrosion started when a sufficiently high chloride concentration was built up

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This paper presents the comparative results obtained from X-ray and neutron pair distribution function (PDF) analysis aimed at determining the variability in aluminosilicate glass chemistry in five types of class F fly ash (FA). Results have been discussed in light of the complementary information provided by the two methods in order to give a comprehensive overview of FA structure at the nanoscale. The analysis of short range correlations reveals that the bulk glassy structure of FA sources differing in chemical composition are relatively similar, but some specific distinctions in atomic structure are visible in those containing high levels of amorphous VIcoordinated aluminum (e.g., amorphous mullite/alumina), iron and/or carbon (with similar local bonding environment to graphite). The obtained experimental results fill a deficit in literature in the atomic structure and associated variability for class F FA, which is extensively used in several industrial applications including as raw material in alkali-activated cements.