Liu Tong, Li Chunqing, Li Li, Fan Wenqiang, Dong Yudong, Liang Huihui, Yang Hongjian
School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin 300130, China.
Tianjin Cheng An Thermal Power Co., Ltd., Tianjin 300161, China.
Materials (Basel). 2022 Feb 11;15(4):1334. doi: 10.3390/ma15041334.
To improve the mechanical performance and lower the production cost of magnesium oxysulfate cement (MOSC), this article investigates the effects of single and compounded addition of metakaolin (MK) and/or fly ash (FA) on the setting time, mechanical strength, water resistance, hydration product, composition, and microstructure of the resulting cement. MOSC samples with different proportions, ranging from 0 to 30 wt.%, of FA and/or MK substituting magnesium oxide (MgO) were prepared. The microstructure was explored by scanning electron microscopy, X-ray diffraction, and mercury intrusion porosimetry. The findings suggest that adding FA can delay the setting of MOSC; however, the effect of adding MK to MOSC was reversed. Furthermore, the phase composition of the MOSC hydration products was unaltered upon adding FA and/or MK, but thicker and longer 517 phase crystals were observed. FA and MK can effectively fill the large pores of MOSC through filling and nucleation effects, reduce the pore size, and form a denser microstructure, thereby improving its mechanical properties. The optimal MOSC sample was found by substituting 10 wt.% of both FA and MK, resulting in a cement that exhibited a short setting time and an incredibly high mechanical strength and density. These findings will further the development of stronger, more cost-efficient, and more water-resistant MOSC products.
为提高硫酸镁水泥（MOSC）的力学性能并降低其生产成本，本文研究了偏高岭土（MK）和/或粉煤灰（FA）单掺及复掺对所得水泥的凝结时间、力学强度、耐水性、水化产物、组成及微观结构的影响。制备了用0至30 wt.%的FA和/或MK替代氧化镁（MgO）的不同比例的MOSC样品。通过扫描电子显微镜、X射线衍射和压汞法对微观结构进行了探究。研究结果表明，添加FA会延迟MOSC的凝结；然而，向MOSC中添加MK的效果则相反。此外，添加FA和/或MK后，MOSC水化产物的相组成未发生改变，但观察到517相晶体更厚且更长。FA和MK可通过填充和成核作用有效填充MOSC的大孔，减小孔径，形成更致密的微观结构，从而改善其力学性能。通过用10 wt.%的FA和MK同时替代，找到了最佳的MOSC样品，得到了一种凝结时间短且具有极高力学强度和密度的水泥。这些发现将推动更强、更具成本效益且更耐水的MOSC产品的发展。
