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<p>When used in cement-based materials, sulfidic minerals such as pyrite may oxidize in the long term and their oxidation products may react with the cementitious matrix. This long-term instability of sulfidic materials is considered a concerning matter for their application in concrete. To evaluate the deterioration potential of sulfidic materials in cementitious materials, test methods involving wet–dry cycles are often used. The present paper investigates the suitability of wet–dry cycles as an accelerated test applied to pyrite-containing cements. Mortars containing sulfidic materials (0–98 wt.% pyrite) as a 30 wt.% replacement for cement were exposed to wet–dry cycles, and their expansion was measured at regular intervals. Changes in phase assemblage were investigated to elucidate the effects of the curing conditions on the binder phase and the extent of oxidation of pyrite. Results show that the wet–dry cycles are ineffective at accelerating the oxidation of pyritic materials within a reasonable timeframe. After 1 year (52 cycles), the mortars do not show expansion, and pyrite oxidation is localized and unsubstantial. Finally, it is demonstrated that the carbonation of samples is an important side effect of the test procedure, which significantly increases the complexity of the analysis. This work has identified the need for revision of the test protocol to effectively promote sulfide oxidation while minimizing the effects of atmospheric carbonation on the specimens. These results are relevant for the valorization of high-volume waste streams, such as sulfidic mine tailings as binder components in cementitious materials.</p>

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Assessment of internal sulfate attack in cement partially replaced with pyritic materials using wet–dry cycles

  • 期刊论文

  • 发表日期：

    2025年6月14日

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  • Natalia Pires Martins,
  • Arne Peys,
  • Jo Lievens,
  • Jan Jordens,
  • Guillaume Habert,
  • Ruben Snellings

摘要

When used in cement-based materials, sulfidic minerals such as pyrite may oxidize in the long term and their oxidation products may react with the cementitious matrix. This long-term instability of sulfidic materials is considered a concerning matter for their application in concrete. To evaluate the deterioration potential of sulfidic materials in cementitious materials, test methods involving wet–dry cycles are often used. The present paper investigates the suitability of wet–dry cycles as an accelerated test applied to pyrite-containing cements. Mortars containing sulfidic materials (0–98 wt.% pyrite) as a 30 wt.% replacement for cement were exposed to wet–dry cycles, and their expansion was measured at regular intervals. Changes in phase assemblage were investigated to elucidate the effects of the curing conditions on the binder phase and the extent of oxidation of pyrite. Results show that the wet–dry cycles are ineffective at accelerating the oxidation of pyritic materials within a reasonable timeframe. After 1 year (52 cycles), the mortars do not show expansion, and pyrite oxidation is localized and unsubstantial. Finally, it is demonstrated that the carbonation of samples is an important side effect of the test procedure, which significantly increases the complexity of the analysis. This work has identified the need for revision of the test protocol to effectively promote sulfide oxidation while minimizing the effects of atmospheric carbonation on the specimens. These results are relevant for the valorization of high-volume waste streams, such as sulfidic mine tailings as binder components in cementitious materials.