Wpływ dodatkowych materiałów cementowych na odporność zapraw na siarczany

Sulfate reaction is a damaging expansive process that deteriorates cement-based structures over time. Various methods have beenproposed to mitigate the effects of sulfate attack in concrete. Using Type II or Type V portland cement is an appealing approach tocontrol sulfate attack. Additionally, incorporating supplementary cementitious materials (SCMs) such as class F fly ash, a byproductof coal combustion for electricity generation, has proven effective at mitigating sulfate attack damage. However, futureavailability of fly ash is uncertain due to the energy industry transitioning towards more sustainable methods of energy productionrather than relying on coal combustion. Consequently, there is an incentive to seek alternative SCMs that can effectively mitigatesulfate attack while being environmentally sustainable and economically feasible. In this study, ASTM C1012, a globallyrecognized standard test method for sulfate evaluation, was employed to assess sulfate resistance of mortar specimens. In total, 14mortar mixtures containing various types and concentrations of alternative SCMs, including silica fume, metakaolin, and pumicitealong with two types of portland cement (Type I and Type I/II) were produced. The results indicated that Type I/II portland cementhad greater sulfate resistance compared to Type I cement in mortar mixtures, regardless of the type and concentration of SCMsused. Additionally, although metakaolin considerably improved sulfate resistance, silica fume and pumicite used in this study hadonly limited impact on sulfate resistance of the specimens. When evaluating ternary mixtures, using a combination of 22.5%metakaolin and 7.5% fly ash to replace 30% of Type I portland cement resulted in the greatest sulfate resistance among all mortarmixtures, with 0.054% expansion after nine months of testing. It is worth mentioning that when using Type I/II portland cementand only 15% metakaolin (as a cement replacement), sulfate resistance was comparable to the ternary mixture with 22.5%metakaolin, 7.5% fly ash, and with Type I portland cement. Overall, the results showed that metakaolin, fly ash, and pumicite canbe considered effective SCMs for improving sulfate resistance.