In contact with natural waters, concrete can be exposed to the action of magnesium. Mg-attack on the cement paste leads to dissolution of cementitious phases and formation of brucite, hydrotalcite and/or magnesium silicate hydrates (M-S-H). The knowledge of the properties of the latter is limited. In binders with supplementary cementitious materials, M-S-H formation is favoured over that of brucite because of the lower contents of portlandite. To investigate the effects of a magnesium attack on such binders, a low Ca/Si model cement paste was immersed in a 5 mmol/L MgCl solution for several months. Energy-dispersive spectrometry analyses coupled with X-ray diffraction and electron probe microanalyses showed Ca leaching, Si preservation and Mg enrichment of the altered zones of the pastes corresponding to the dissolution of C-S-H and formation of M-S-H and amorphous silica. The Mg-enriched zone showed a lower residual Young's modulus than the sound zone as measured by microindentation.

中文翻译：

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含镁环境中低 pH 模型水泥浆的化学机械特性


在与天然水接触时，混凝土会受到镁的作用。水泥浆体上的镁侵蚀导致胶结相溶解并形成水镁石、水滑石和/或硅酸镁水合物（MSH）。对后者属性的了解是有限的。在具有辅助胶凝材料的粘结剂中，由于硅钙石含量较低，MSH 的形成优于水镁石。为了研究镁侵蚀对此类粘合剂的影响，将低 Ca/Si 模型水泥浆浸入 5 mmol/L MgCl 溶液中几个月。能量色散光谱分析与 X 射线衍射和电子探针微量分析相结合，表明浆料蚀变区存在 Ca 浸出、Si 保存和 Mg 富集，这与 CSH 的溶解以及 MSH 和无定形二氧化硅的形成相对应。通过微压痕测量，富镁区的残余杨氏模量比健全区低。