Wpływ dodatkowych materiałów cementowych na odporność zapraw na siarczany

Seyedsaleh Mousavinezhad; William K. Toledo; Craig M.  Newtson; Federico Aguayo

doi:10.29227/IM-2024-02-9

Seyedsaleh Mousavinezhad Department of Civil Engineering, New Mexico State University, Las Cruces, NM 88003, USA
William K. Toledo Sandia National Laboratories, Albuquerque, NM 87123, USA; e-mail: wktoledo@nmsu.edu
Craig M. Newtson Department of Civil Engineering, New Mexico State University, Las Cruces, NM 88003, USA
Federico Aguayo Department of Civil and Environmental Engineering, University of Washington, Seattle, WA 98195

DOI: https://doi.org/10.29227/IM-2024-02-9

Słowa kluczowe: popiół lotny, metakaolin, mieszanki zapraw, pumeks, pył krzemionkowy, odporność na siarczany

Abstrakt

Sulfate reaction is a damaging expansive process that deteriorates cement-based structures over time. Various methods have been
proposed to mitigate the effects of sulfate attack in concrete. Using Type II or Type V portland cement is an appealing approach to
control sulfate attack. Additionally, incorporating supplementary cementitious materials (SCMs) such as class F fly ash, a byproduct
of coal combustion for electricity generation, has proven effective at mitigating sulfate attack damage. However, future
availability of fly ash is uncertain due to the energy industry transitioning towards more sustainable methods of energy production
rather than relying on coal combustion. Consequently, there is an incentive to seek alternative SCMs that can effectively mitigate
sulfate attack while being environmentally sustainable and economically feasible. In this study, ASTM C1012, a globally
recognized standard test method for sulfate evaluation, was employed to assess sulfate resistance of mortar specimens. In total, 14
mortar mixtures containing various types and concentrations of alternative SCMs, including silica fume, metakaolin, and pumicite
along with two types of portland cement (Type I and Type I/II) were produced. The results indicated that Type I/II portland cement
had greater sulfate resistance compared to Type I cement in mortar mixtures, regardless of the type and concentration of SCMs
used. Additionally, although metakaolin considerably improved sulfate resistance, silica fume and pumicite used in this study had
only 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 mortar
mixtures, with 0.054% expansion after nine months of testing. It is worth mentioning that when using Type I/II portland cement
and 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 can
be considered effective SCMs for improving sulfate resistance.