Xie Lilan, Deng Min, Tang Jinhui, Liu Kaiwei
College of Materials Science and Engineering, Nanjing Tech University, Nanjing 211816, China.
College of Materials and Construction Engineering, Guizhou Normal College, Guiyang 550018, China.
Materials (Basel). 2021 Jan 21;14(3):508. doi: 10.3390/ma14030508.
To rationally use low-grade phosphorous limestone as the raw materials for cement production, the influence of phosphorous introduced by fluorapatite during the clinker calcination process on the mechanical properties of cementitious materials is investigated. Hydration kinetics, phase evolutions, and microstructure of cement pastes have been studied by using calorimetry, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results indicate that the mechanical properties of cementitious materials can be slightly improved due to the mineralization effect of the small amount of phosphorous in the clinker and significantly decreased with an increase of phosphorous. High content of phosphorous will reduce the content of CS and make the formation of α'-CS-xCP(x: 0-0.05), whose hydration reactivity is rather lower, such that on the one hand less-hydrated products, such as calcium silicate hydrate (C-S-H) gel, can be obtained, and on the other hand, the hydration reaction will be slowed by severely prolonging the induction period. Interestingly, small particles can be observed on the surface of hydration products, but no new phase can be detected by XRD. When the content of PO is 2.0%, the cement can meet the requirements of P·II 42.5 cement in China. Hopefully, this can provide significant guidance for the use of cement prepared by fluorapatite as raw material.
为合理利用低品位磷灰岩作为水泥生产原料，研究了氟磷灰石在熟料煅烧过程中引入的磷对胶凝材料力学性能的影响。通过量热法、X射线衍射（XRD）和扫描电子显微镜（SEM）研究了水泥浆体的水化动力学、相演变和微观结构。结果表明，由于熟料中少量磷的矿化作用，胶凝材料的力学性能可略有改善，但随着磷含量的增加显著降低。高磷含量会降低CS的含量，并促使形成水化活性较低的α'-CS-xCP（x：0-0.05），使得一方面可获得较少的水化产物，如水化硅酸钙（C-S-H）凝胶，另一方面，水化反应会因诱导期严重延长而减慢。有趣的是，在水化产物表面可观察到小颗粒，但XRD未检测到新相。当PO含量为2.0%时，该水泥可满足我国P·II 4。5水泥的要求。希望这能为以氟磷灰石为原料制备水泥的使用提供重要指导。
