Fan Zhiyuan, Mao Zhongyang, Liu Xiang, Yi Lei, Zhang Tao, Huang Xiaojun, Deng Min
College of Materials Science and Engineering, Nanjing Tech University, Nanjing 211800, China.
State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing 211800, China.
Materials (Basel). 2022 Jun 9;15(12):4109. doi: 10.3390/ma15124109.
Dolostone is widely distributed and commonly used as concrete aggregates. A large number of studies have shown that there are significant differences in the expansibility of different dolostones, and the key factors determining the expansibility of alkali carbonate rocks have not been clarified. In this paper, rocks were selected from five different geological ages: Jixianian, Cambrian, Ordovician, Devonian, and Triassic ages. The ordering degree and the content of MgCO of dolomites in rocks of different geological ages were determined by X-ray diffraction (XRD). The degree of dedolomitization reaction in rocks cured in 80 °C, 1 mol/L NaOH solution was determined by quantitative X-ray diffraction (QXRD). The morphology of dolomites in rocks was determined by a polarizing microscope. The products of the dedolomitization reaction were determined by field emission electron microscopy (FESEM-EDS). According to the test results, the following conclusions are drawn. There is a good positive correlation between ordering degree and the molar fraction of MgCO of dolomites. When the MgCO mole fraction of dolomites varies from 47.17% to 49.60%, the higher the MgCO mole fraction, the greater the ordering degree of dolomite. By analyzing the degree of the dedolomitization reaction of different dolostone powders cured at 80 °C in 1 mol/L NaOH solution, it is found that the older the geological age of dolostone, the slower the dedolomitization reaction rate and the lower the degree of dedolomitization reaction. The lower the ordering degree of dolomite crystal in the same geological age, the faster the rate of dedolomitization reaction and the higher the degree of dedolomitization reaction.
白云岩分布广泛，常用作混凝土骨料。大量研究表明，不同白云岩的膨胀性存在显著差异，且决定碱碳酸盐岩膨胀性的关键因素尚未明确。本文选取了五个不同地质年代的岩石：蓟县系、寒武系、奥陶系、泥盆系和三叠系。通过X射线衍射（XRD）测定不同地质年代岩石中白云石的有序度和MgCO₃含量。通过定量X射线衍射（QXRD）测定在80℃、1mol/L NaOH溶液中养护的岩石中脱白云石化反应程度。用偏光显微镜测定岩石中白云石的形态。用场发射电子显微镜（FESEM - EDS）测定脱白云石化反应产物。根据试验结果，得出以下结论。白云石的有序度与MgCO₃摩尔分数之间存在良好的正相关关系。当白云石的MgCO₃摩尔分数在47.17%至49.60%之间变化时，MgCO₃摩尔分数越高，白云石的有序度越大。通过分析不同白云岩粉末在80℃、1mol/L NaOH溶液中养护时的脱白云石化反应程度，发现白云岩的地质年代越老，脱白云石化反应速率越慢，脱白云石化反应程度越低。在相同地质年代中，白云石晶体的有序度越低，脱白云石化反应速率越快，脱白云石化反应程度越高。
