Institute of Urban Smart Transportation Safety Maintenance, Shenzhen University, Shenzhen, Guangdong Province, 518061, PR China.
School of Civil Engineering, Central South University, Changsha 410075, China.
Sci Total Environ. 2022 Jul 10;829:154546. doi: 10.1016/j.scitotenv.2022.154546. Epub 2022 Mar 14.
The development of magnesium oxychloride cement can effectively utilize the waste of potash industry and reduce its harm to the environment. Although magnesium oxychloride cement paste (MOCP) has excellent performance in dry environment, its performance is greatly deteriorated in water or humid environment, which severely limits its practical application. In order to improve the water resistance of MOCP, MOCP was modified by various gypsum in this study, and the intrinsic mechanism was explored. Results showed that replacing MgO with gypsum delayed the setting time of MOCP and effectively improved its volume stability. Although the incorporation of gypsum reduced the 14-d air-cured compressive strength of MOCP, waste gypsum was able to significantly improve the water resistance of MOCP compared to natural gypsum. When 80% flue gas desulfurization gypsum and phosphogypsum (weight of magnesium oxide) were incorporated into MOCP, the 14-d air-cured compressive strength of MOCP was only decreased by 14.49% and 15.94% compared with the control group, but its 28-d water immersion strength retention coefficient (SRC) could still reach 61.02% and 46.55%, respectively. However, for the control group and MOCP with 80% natural gypsum, the 28-d SRC were only 28.99% and 8.41%. The incorporation of high-volume waste gypsum to MOCP not only reduced the relative content of MgO, but also improved the stability of the 5-phase in water, which was beneficial to improve the water resistance of MOCP. In addition, high-volume waste gypsum-modified MOCP had lower cost and carbon emissions, and exhibited superior water resistance and sustainability compared to existing MOCP compositions.
氧氯化镁水泥的发展可以有效利用钾工业的废物，减少其对环境的危害。尽管氧氯化镁水泥浆（MOCP）在干燥环境中具有优异的性能，但在水或潮湿环境中其性能会大大恶化，这严重限制了其实际应用。为了提高 MOCP 的耐水性，本研究用各种石膏对 MOCP 进行了改性，并探讨了其内在机理。结果表明，用石膏替代部分氧化镁可以延缓 MOCP 的凝结时间，并有效地提高其体积稳定性。尽管掺入石膏会降低 MOCP 的 14 天空气养护抗压强度，但与天然石膏相比，废石膏能够显著提高 MOCP 的耐水性。当 80%烟气脱硫石膏和磷石膏（氧化镁的重量）掺入 MOCP 中时，MOCP 的 14 天空气养护抗压强度仅比对照组降低了 14.49%和 15.94%，但其 28 天浸水强度保留系数（SRC）仍分别达到 61.02%和 46.55%。然而，对于对照组和掺入 80%天然石膏的 MOCP，28 天 SRC 仅为 28.99%和 8.41%。将大量废石膏掺入 MOCP 中不仅降低了氧化镁的相对含量，而且提高了 5 相在水中的稳定性，有利于提高 MOCP 的耐水性。此外，与现有 MOCP 组成相比，大量废石膏改性的 MOCP 具有更低的成本和碳排放，并且具有更好的耐水性和可持续性。
