Fly ash is the main solid waste produced from coal-fired power plants, which has been extensively used as a mineral admixture for concrete and cement. In this paper, the effects of fly ash on the compressive strength, water resistance, setting time, phase composition and microstructure of magnesium oxysulfate (MOS) cement modified with 0.5% sodium dihydrogen phosphate (NaH₂PO₄) were investigated. X-ray diffraction and the Rietveld method were used to analyze the phase composition. Scanning electron microscopy and mercury intrusion porosimetry were conducted to characterize the microstructure. The results reveal that the addition of fly ash can decrease the compressive strength but improve the water resistance of MOS cement. Due to the dilution effect of fly ash, the setting time of MOS cement increases with the increase in the amount of fly ash. Although the filling effect or pozzolanic effect of fly ash brings an improvement in the microstructure of MOS cement, the addition of fly ash reduces the formation amount of 5Mg(OH)₂·MgSO₄·7H₂O, which is an important factor affecting the strength development of MOS cement.

中文翻译：

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粉煤灰对氧硫酸镁水泥性能的影响

粉煤灰是燃煤发电厂产生的主要固体废物，已被广泛用作混凝土和水泥的矿物掺合料。本文研究了粉煤灰对0.5％磷酸二氢钠（NaH ₂ PO ₄）改性的氧硫酸镁（MOS）水泥的抗压强度，耐水性，凝结时间，相组成和微观结构的影响。）进行了调查。用X射线衍射和Rietveld方法分析相组成。进行了扫描电子显微镜和压汞法测定其微观结构。结果表明，粉煤灰的添加可降低抗压强度，但可提高MOS水泥的耐水性。由于粉煤灰的稀释作用，MOS水泥的凝结时间随粉煤灰量的增加而增加。尽管粉煤灰的填充作用或火山灰作用改善了MOS水泥的微观结构，但添加粉煤灰却减少了5Mg（OH）₂ ·MgSO ₄ ·7H ₂ O的形成量，这是影响粉煤灰形成的重要因素。 MOS水泥的强度发展。