Madej Dominika
AGH University of Science and Technology, Faculty of Materials Science and Ceramics, al. A. Mickiewicza 30, 30-059 Krakow, Poland.
Materials (Basel). 2020 May 21;13(10):2366. doi: 10.3390/ma13102366.
This work concerns the hydration mechanism of calcium zirconium aluminate as a ternary compound appearing in the CaO-AlO-ZrO diagram besides the calcium aluminates commonly used as the main constitutes of calcium aluminate cements (CACs). Moreover, a state-of-the-art approach towards significant changes in hydraulic properties was implemented for the first time in this work, where the effect of structural modification on the hydration behavior of calcium zirconium aluminate was proved by XRD, Al MAS NMR and SEM-EDS. The substitution of Sr for Ca in the CaZrAlO lattice decreases the reactivity of Sr-substituted CaZrAlO in the presence of water. Since the original cement grains remain unhydrated up to 3 h (CaZrAlO) or 72 h (SrCaZrAlO) of curing period in the hardened cement paste structures, strontium can be considered as an inhibition agent for cement hydration. The complete conversion from anhydrous Al to hydrated Al species was achieved during the first 24 h (CaZrAlO) or 7 d(SrCaZrAlO) of hydration. Simultaneously, the chemical shift in the range of octahedral aluminum from ca. 4 ppm to ca. 6 ppm was attributed to the transformation of the hexagonal calcium aluminate hydrates and Sr-rich (Sr,C)AH hydrate into the cubic phase Ca-rich (Sr,C)AH or pure CAH in the hardened Sr-doped cement paste at the age of 7 d. The same Al NMR chemical shift was detected at the age of 24 h for the reference hardened undoped CaZrAlO cement paste.
本研究关注铝酸钙锆（一种三元化合物）的水化机理，它出现在CaO - AlO - ZrO相图中，是除了常用作铝酸钙水泥（CACs）主要成分的铝酸钙之外的化合物。此外，本研究首次采用了一种先进方法来研究水硬性的显著变化，通过XRD、Al MAS NMR和SEM - EDS证明了结构改性对铝酸钙锆水化行为的影响。在CaZrAlO晶格中用Sr取代Ca会降低Sr取代的CaZrAlO在有水存在时的反应活性。由于在硬化水泥浆体结构中，原始水泥颗粒在养护期3小时（CaZrAlO）或72小时（SrCaZrAlO）内仍未水化，因此锶可被视为水泥水化的抑制剂。在水化的前24小时（CaZrAlO）或7天（SrCaZrAlO）内实现了从无水Al到水合Al物种的完全转化。同时，八面体铝化学位移从约4 ppm到约6 ppm的变化归因于在7天大的掺Sr硬化水泥浆体中，六方铝酸钙水合物和富Sr（Sr，C）AH水合物向立方相富Ca（Sr，C）AH或纯CAH的转变。对于参考未掺杂的硬化CaZrAlO水泥浆体，在24小时龄期时检测到相同的Al NMR化学位移。
