硝酸钙溶液中脱硫石膏制备α-半水石膏及硫酸钾的作用
发布时间：2018-07-17 07:15
【摘要】：α-半水石膏是重要的胶凝材料,因其优良的性能广泛应用于建材、医学、模具等领域。常压盐溶液法制备α-半水石膏,反应条件温和、产品稳定,是最具前景的制备技术。其中,反应介质是常压盐溶液法最为重要的影响因素之一。本文研究了常压温和条件下Ca(NO3)2水溶液中脱硫石膏制备α-半水石膏的工艺,重点研究了K2SO4对脱硫石膏脱水过程、α-半水石膏形貌的影响以及不同条件下得到的产物的水化强度。为实现脱硫石膏制备α-半水石膏,常用的结晶介质体系为CaCl2水溶液,但是氯根会导致材料腐蚀等问题。本实验以Ca(NO3)2取代CaCl2,在95℃及常压条件下,实现脱硫石膏顺利转化为α-半水石膏,形成了新的脱硫石膏制备a-半水石膏的工艺。通过不同K2SO4浓度对脱硫石膏脱水过程、α-半水石膏形貌的研究,结果表明,K2SO4浓度由0 mM增加至87.50 mM,脱硫石膏的完全转化时间逐渐缩短,由11h缩短至3h。其中对α-半水石膏的诱导成核时间影响比对晶体生长时间影响更为显著。K2SO4对脱硫石膏转化速率的影响是K+和SO42-的共同作用,其中SO42-对转化速率的促进作用大于K+。K2SO4还对α-半水石膏晶体粒径有十分显著的影响,随着K2SO4浓度由0 mM增加到87.50 mM,晶体长度由354.28μm减小为55.11μm,直径由48.88μm减小至10.81μm,长径比由7.25降低至5.10。a-半水石膏最重要的性能是其胶凝体的强度。α-半水石膏的水化过程遵循“溶解-析晶”原理,在水化过程中形成交织连生的二水石膏胶凝体。当K2S04浓度从0mM增加到87.50 mM,α-半水石膏的胶凝体2h抗折强度、抗压强度分别由5.62 MPa降低至2.47 MPa,11.20 MPa降低至4.10 MPa；绝干抗折强度、抗压强度分别由9.63 MPa降低至5.72 MPa,22.90 MPa降低至16.83 MPa。α-半水石膏水化后的二水石膏晶体粒径增大,晶体形貌由板状、薄片状向针柱状转变,晶体间的相互搭接较为疏松,增加了胶凝体的孔径,使得胶凝体的结构趋于疏松,导致其强度降低。研究表明,95℃及常压条件下,脱硫石膏在Ca(NO3)2溶液中快速转化为α-半水石膏,并且a-半水石膏水化后能够得到强度较高的胶凝体,形成了新的制备工艺。通过添加K2S04调节脱硫石膏脱水转化为α-半水石膏的速率、控制α-半水石膏晶体形貌,从而影响胶凝体性能。
[Abstract]:伪-hemihydrate gypsum is an important cementitious material, because of its excellent properties, it is widely used in the fields of building materials, medicine, mould and so on. The preparation of 伪-hemihydrate gypsum by salt solution under normal pressure is the most promising preparation technology with mild reaction conditions and stable products. Among them, the reaction medium is one of the most important influencing factors in the method of salt solution under atmospheric pressure. The preparation of 伪 -hemihydrate gypsum from desulfurized gypsum in Ca (no _ 3) _ 2 aqueous solution under normal pressure and temperature was studied in this paper. The effect of K _ 2SO _ 4 on the dehydration process, the morphology of 伪 -hemihydrate gypsum and the hydration strength of the product obtained under different conditions were studied. In order to prepare 伪 -hemihydrate gypsum from desulphurized gypsum, CaCl _ 2 aqueous solution is commonly used as crystallization medium, but chloride can lead to material corrosion and so on. In this experiment, Ca (no _ 3) _ 2 was used to replace CaCl _ 2. Under the condition of 95 鈩，
本文编号：2129557
[Abstract]:伪-hemihydrate gypsum is an important cementitious material, because of its excellent properties, it is widely used in the fields of building materials, medicine, mould and so on. The preparation of 伪-hemihydrate gypsum by salt solution under normal pressure is the most promising preparation technology with mild reaction conditions and stable products. Among them, the reaction medium is one of the most important influencing factors in the method of salt solution under atmospheric pressure. The preparation of 伪 -hemihydrate gypsum from desulfurized gypsum in Ca (no _ 3) _ 2 aqueous solution under normal pressure and temperature was studied in this paper. The effect of K _ 2SO _ 4 on the dehydration process, the morphology of 伪 -hemihydrate gypsum and the hydration strength of the product obtained under different conditions were studied. In order to prepare 伪 -hemihydrate gypsum from desulphurized gypsum, CaCl _ 2 aqueous solution is commonly used as crystallization medium, but chloride can lead to material corrosion and so on. In this experiment, Ca (no _ 3) _ 2 was used to replace CaCl _ 2. Under the condition of 95 鈩，
本文编号：2129557
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