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Knowledge of the durability and related properties of alkali-activated materials is a prerequisite for their application as building materials. However, to date only limited data exists in this regard. The present contribution focuses on durability-related transport properties of geopolymer-based materials. We present results of accelerated carbonation, rapid chloride migration (RCM) and air permeability measurements, together with strength and porosity data, for fly ash-based geoplymers, including formulations containing ground granulated blast furnace slag (GGBFS).
It was found that, despite comparable total porosities, the carbonation depths, the chloride migration coefficients and the air permeabilities of the mortars differed significantly. In general, the addition of GGBFS to the binders improved the performance (decreased transport coefficients); however, this was not found to be true for the air permeability in all cases. This latter effect can be explained by drying damage of the C-(A-)S-H gel in GGBFS-containing binders. On the other hand, low transport coefficients can also be achieved by optimization of the binder formulation without the addition of GGBFS, which is also reflected in the material’s air permeability. Thus, there exists no simple correlation between air permeability (of harshly dried mortars) and durability-related transport coefficients for the studied alkali-activated materials.
In addition, corrosion potential, polarization resistance data and current density-potential curves of carbon steel in two of the geopolymer mortars are presented. The corrosion potential vs. time curves in combination with polarization resistance values reveal that the steel reinforcement in geopolymer mortars assumed a passive state. However, this happened considerably later than for steel in CEM I-based mortars.