Boháč Martin, Zezulová Anežka, Krejčí Kotlánová Michaela, Kubátová Dana, Staněk Theodor, Krejza Zdeněk, Všianský Dalibor, Novotný Radek, Palovčík Jakub, Dvořák Karel
Research Institute for Building Materials, Brno, Czech Republic.
Faculty of Science, Department of Geological Sciences, Masaryk University, Brno, Czech Republic.
J Microsc. 2024 May;294(2):168-176. doi: 10.1111/jmi.13280. Epub 2024 Feb 28.
CAF is considered the least reactive main clinker phase, but its reactivity may be affected by adding supplementary cementitious materials (SCMs). Pure CAF was synthesised in a laboratory furnace, and the role of silica fume without gypsum on its early hydration properties was monitored. Burning was carried out in four stages to achieve 99% purity of CAF. Heat flow development was monitored by isothermal calorimetry over 7 days of hydration at 20°C and 40°C. The role of silica fume on hydrogarnet phase katoite (CaAl(SiO) (OH) x = 1.5-3) formation during early hydration was studied. Rapid dissolution of CAF, formation of metastable C-(A,F)-H and its conversion to C(A, F)H was evidenced by isothermal calorimetry as a large exotherm. Changes in microstructure during early hydration were documented by SE micrographs, EDS point analyses, X-ray mapping and line scans by SEM-EDS. The phase composition was characterised by DTA-TGA and QXRD after 7 days of hydration. The katoite diffraction pattern is similar for the reference sample and sample with silica fume, but substitution in its structure can be revealed by X-ray microanalyses. The composition of katoite is variable due to the various extent of substitution of 4OH by SiO due to silica fume.
钙铝铁榴石被认为是活性最低的主要熟料相，但其活性可能会受到添加辅助胶凝材料（SCMs）的影响。在实验室炉中合成了纯钙铝铁榴石，并监测了无石膏硅灰对其早期水化性能的作用。燃烧分四个阶段进行，以实现钙铝铁榴石99%的纯度。通过等温量热法在20°C和40°C下水化7天监测热流发展。研究了硅灰在早期水化过程中对水石榴石相六方水钙铝榴石（CaAl(SiO)(OH) x = 1.5 - 3）形成的作用。等温量热法显示，钙铝铁榴石的快速溶解、亚稳C-(A,F)-H的形成及其向C(A,F)H的转化表现为大量放热。通过扫描电子显微镜（SE）显微照片、能谱点分析、X射线映射以及扫描电子显微镜-能谱（SEM-EDS）线扫描记录早期水化过程中的微观结构变化。水化7天后，通过差示热分析-热重分析（DTA-TGA）和定量X射线衍射（QXRD）对相组成进行表征。参考样品和含硅灰样品的六方水钙铝榴石衍射图谱相似，但通过X射线微分析可以揭示其结构中的取代情况。由于硅灰导致4OH被SiO不同程度地取代，六方水钙铝榴石的组成是可变的。
