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<p>This study investigated the role of MgO/Cl<sub>2</sub> (<i>M</i>) and H<sub>2</sub>O/Cl<sub>2</sub> (<i>H</i>) molar ratios on microstructure and strength degradation of magnesium oxychloride cement (MOC) when exposed to water. The <i>M</i> or <i>H</i> molar ratios were systematically varied (<i>M</i> of 5, 9, or 13; <i>H</i> from 10 to 30) by adjusting the proportions of raw materials and water. Experimental characterization included isothermal calorimetry, X-ray diffraction, thermogravimetric analysis, mercury intrusion porosimetry, and compressive strength measurements before and after water exposure. The test results indicate that low <i>M</i> molar ratios promote a greater heat of hydration and the formation of Phases 3 and 5 as dominant hydration products, resulting in higher compressive strength and lower porosity, along with reduced strength degradation upon water exposure. Conversely, a high <i>M</i> molar ratio of 13 leads to brucite-dominant phase assemblages exceeding 91 wt.%, substantially reducing compressive strength. Furthermore, increasing <i>H</i> molar ratios contributes to additional brucite formation and a further reduction in compressive strength.</p>

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Role of MgO/Cl2 and H2O/Cl2 Molar Ratios on Microstructure and Strength Degradation of Magnesium Oxychloride Cement When Exposed to Water

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年6月19日

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  • Inzimam Ul Haq,
  • Jin-Ho Bae,
  • Naru Kim,
  • Ahmad Nawaz,
  • Jihoon Park,
  • Hammad R. Khalid,
  • H. K. Lee

摘要

This study investigated the role of MgO/Cl2 (M) and H2O/Cl2 (H) molar ratios on microstructure and strength degradation of magnesium oxychloride cement (MOC) when exposed to water. The M or H molar ratios were systematically varied (M of 5, 9, or 13; H from 10 to 30) by adjusting the proportions of raw materials and water. Experimental characterization included isothermal calorimetry, X-ray diffraction, thermogravimetric analysis, mercury intrusion porosimetry, and compressive strength measurements before and after water exposure. The test results indicate that low M molar ratios promote a greater heat of hydration and the formation of Phases 3 and 5 as dominant hydration products, resulting in higher compressive strength and lower porosity, along with reduced strength degradation upon water exposure. Conversely, a high M molar ratio of 13 leads to brucite-dominant phase assemblages exceeding 91 wt.%, substantially reducing compressive strength. Furthermore, increasing H molar ratios contributes to additional brucite formation and a further reduction in compressive strength.