Comparative study on modifications of pH-adjusted fluorogypsum by potassium carbonate and potassium bicarbonate
Comparative study on modifications of pH-adjusted fluorogypsum by potassium carbonate and potassium bicarbonate
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DOI：
10.1016/j.conbuildmat.2023.131069
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发表时间：
2023-05
影响因子：
7.4
通讯作者：
Hang He;Yuli Wang;Junjie Wang;Shuishan Wang;Rong Huang;Lifan Zheng;Yahong Ding
中科院分区：
文献类型：
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作者：
Hang He;Yuli Wang;Junjie Wang;Shuishan Wang;Rong Huang;Lifan Zheng;Yahong Ding
针对工业副产物氟石膏水化活性差、难以利用的问题，通过水化速率、水化热、溶解度和显微镜测试，研究并比较了碳酸钾（K2 CO 3）和碳酸氢钾（KHCO 3）对氟石膏（pH调至7.3）水化机理的影响。结果表明，K2 CO 3和KHCO 3均能显著提高氟石膏的水化速率和水化放热速率，加速氟石膏的水化过程。K2 CO 3和KHCO 3的最佳含量分别为1%和0.5%，养护3天后，氟石膏的抗压强度由对照组的3.5 MPa提高到20.3 MPa（提高480%）和18.5 MPa（提高429%）。二者均增加了氟石膏的溶解度、二水石膏的过饱和度、二水石膏的成核和生长速率，抑制了二水石膏的溶解。硬化氟石膏的致密性得到提高，气孔率降低。发现K2 CO 3比KHCO 3更有效，导致更高的早期强度。两者的促进机理也有所不同：K2 CO 3通过形成不稳定的复盐正长岩促进氟石膏水化;而KHCO 3主要通过不稳定的硫酸氢钾的“催化作用”促进二水石膏的形成。加入这两种改性剂后，二水石膏的晶体形貌由板状变为柱状或针状，有利于强度的发展。
In view of the poor hydration activity and difficult utilization of industrial by-product fluorogypsum, the effects of potassium carbonate (K2CO3) and potassium bicarbonate (KHCO3) on the hydration mechanisms of fluorogypsum (pH-adjusted to 7.3) were investigated and compared through hydration rate, hydration heat, solubility and microscopic tests. The results show that both K2CO3and KHCO3could significantly increase the hydration rate, hydration heat release rate, and accelerate the hydration process of fluorogypsum. The optimum contents of K2CO3and KHCO3were found to be 1% and 0.5%, respectively, and the compressive strength of the fluorogypsum increased from 3.5 MPa (control group) to 20.3 MPa (increase by 480%) and 18.5 MPa (increase by 429%) after curing for 3 days. Both of the two increased the solubility of fluorogypsum, supersaturation of dihydrate gypsum, the nucleation and growth rate of dihydrate gypsum, and inhibited the dissolution of dihydrate gypsum. The compactness of the hardened fluorogypsum was improved and the porosity was reduced. K2CO3was found to be more effective than KHCO3, resulting in a higher early strength. The acceleration mechanisms of the two were also found to be different: K2CO3increased the hydration of fluorogypsum by forming an unstable double salt syngenite; while KHCO3mainly promoted the formation of dihydrate gypsum through a ‘catalysis effect’ by unstable potassium bisulfate. With the addition of any of these two modifiers, the crystal morphology of dihydrate gypsum was changed from plate to column or needle, which was beneficial for the strength development.