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Changes in cement paste during accelerated mortar bar testing for pyrrhotite containing aggregate
Cement and Concrete Research ( IF 10.9 ) Pub Date : 2024-12-02 , DOI: 10.1016/j.cemconres.2024.107730
K. De Weerdt, M. Bagheri, J. Lindgård, H. Lindstad, A. Rodrigues, J. Duchesne, P.-L. Fecteau, M.K. Haugen, T. Danner, B.J. Wigum, N. Oberhardt, K. Aasly, B. Lothenbach

The accelerated mortar bar test (AMBT) for pyrrhotite (Fe1-xS) containing aggregates accelerates expansion using two regimes: Phase I, during which Fe1-xS oxidation to iron hydroxide is accelerated by bleach and storage at 80 °C; Phase II that promotes thaumasite formation with continued bleach soaking and storage at 4 °C. Two bleach concentrations and one aggregate containing 0.5 wt% Fe1-xS are tested. SEM-EDX data indicate that the oxidized iron precipitates as iron hydroxide at the place of the Fe1-xS, leading to significant expansion (0.22%) during Phase I. The released S distributes in the cement paste but leads only to limited amount of additional ettringite and thaumasite and thus only to limited expansion (0.07%). The NaOCl bleach reduced during the test resulting in chloride and thus to Friedel's salt formation and ettringite stabilization at 80 °C. Only during the prolongation of Phase II, the formation of thaumasite and additional expansion was observed.

中文翻译:


含磁黄铁矿骨料的加速砂浆棒测试过程中水泥浆的变化



含有聚集体的磁黄铁矿 (Fe1-xS) 的加速砂浆条测试 (AMBT) 使用两种方案加速膨胀:第一阶段,在此期间,Fe1-xS 氧化为氢氧化铁通过漂白剂加速并在 80 °C 下储存;第二阶段,通过持续浸泡漂白剂并在 4 °C 下储存来促进奇石的形成。 测试了两种漂白剂浓度和一种含有 0.5 wt% Fe1-xS 的聚集体。SEM-EDX 数据表明,氧化铁在 Fe1-xS 的位置以氢氧化铁的形式沉淀,导致第一阶段显着膨胀 (0.22%)。释放的 S 分布在水泥浆中,但只导致有限量的额外钙矾石和奇石,因此只导致有限的膨胀 (0.07%)。NaOCl 漂白剂在测试过程中减少,导致氯化物,从而在 80 °C 下形成傅氏盐和钙矾石稳定。 仅在第二阶段的延长期间,观察到奇石的形成和额外的膨胀。
更新日期:2024-12-02
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