Technische Universität München, Lehrstuhl für Bauchemie, Lichtenbergstr, 4, 85747 Garching bei München, Germany.
Spectrochim Acta A Mol Biomol Spectrosc. 2013 Jul;111:299-303. doi: 10.1016/j.saa.2013.04.033. Epub 2013 Apr 11.
Micro-Raman spectroscopy has been used to follow the reaction of free lime (CaO) exposed for 24h to moist air at 80 °C under conditions of different relative humidities (10-80% RH). X-ray diffraction and SEM imaging were applied as complementary techniques. The conversion of lime to calcium hydroxide and its subsequent carbonation to various calcium carbonate polymorphs was found to strongly depend on the relative humidity. At low RH (10-20%), only Raman spectroscopy revealed the formation of early amorphous CaCO3 which in the XRD patterns was detected only at ≥40% RH. However, XRD analysis could identify the crystalline polymorphs formed at higher relative humidities. Thus, between 20 and 60% RH, all three CaCO3 polymorphs (calcite, aragonite and vaterite) were observed via XRD whereas at high relative humidity (80%), calcite was the predominant reaction product. The results demonstrate the usefulness of Raman spectroscopy in the study of minor cement constituents and their reaction products on air, especially of amorphous character.
微拉曼光谱已被用于研究游离石灰（CaO）在 80°C 下、相对湿度为 10-80%的潮湿空气中暴露 24 小时的反应。X 射线衍射和扫描电子显微镜成像被用作补充技术。结果表明，石灰转化为氢氧化钙，随后碳化生成各种碳酸钙多晶型物，这强烈依赖于相对湿度。在低 RH（10-20%）下，只有拉曼光谱显示出早期无定形 CaCO3 的形成，而在 XRD 图谱中仅在≥40% RH 时才能检测到。然而，XRD 分析可以识别在较高相对湿度下形成的结晶多晶型物。因此，在 20 至 60% RH 之间，XRD 观察到了所有三种 CaCO3 多晶型物（方解石、文石和球霰石），而在高相对湿度（80%）下，方解石是主要的反应产物。研究结果表明，拉曼光谱在研究空气中的水泥次要成分及其反应产物方面非常有用，特别是对无定形物质的研究。
