Wang Feng, Chen Pingan, Li Xiangcheng, Zhu Boquan
The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China.
Materials (Basel). 2018 Sep 28;11(10):1849. doi: 10.3390/ma11101849.
The effect of colloidal silica (CS) on the hydrate phases and microstructure evolution of calcium aluminate cement (CAC) was investigated. Samples hydrated with CS were obtained and characterized by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared spectroscopy (FT-IR), hydration heat measurement and Nuclear Magnetic Resonance (NMR). The results revealed that SiO₂ nanoparticles may affect the hydrates crystallization process. There was a compact structure in the CAC paste with CS, while petal-shaped hydrates with a porous structure were formed in the pure CAC paste. The maximum value of electrical conductivity for CAC paste with CS suggested that the early stage of hydration for CAC was accelerated. However, the hydration heat curves revealed that the late stage of the CAC hydration process was inhibited, and the hydration degree was reduced, this result was in accordance with Thermogravimetry-Differential scanning calorimetry(TG-DSC) curves. The fitting results of hydration heat curves further showed that the hydration degree at NG (nucleation and crystal growth) process stage was promoted, while it was limited at the phase boundaries stage, and the diffusion stage in the hydration reaction was brought forward due to the addition of CS. According to these results and analyses, the differences in the hydration process for CAC with and without CS can be attributed to the distribution and nucleation effect of SiO₂ nanoparticles.
研究了胶体二氧化硅（CS）对铝酸钙水泥（CAC）水合物相和微观结构演变的影响。制备了用CS水化的样品，并通过X射线衍射（XRD）、场发射扫描电子显微镜（FESEM）、傅里叶变换红外光谱（FT-IR）、水化热测量和核磁共振（NMR）对其进行了表征。结果表明，SiO₂纳米颗粒可能会影响水合物的结晶过程。含CS的CAC浆体具有致密结构，而纯CAC浆体中形成了具有多孔结构的花瓣状水合物。含CS的CAC浆体的电导率最大值表明CAC的水化早期得到了加速。然而，水化热曲线表明，CAC水化过程的后期受到抑制，水化程度降低，这一结果与热重-差示扫描量热法（TG-DSC）曲线一致。水化热曲线的拟合结果进一步表明，在成核与晶体生长（NG）过程阶段水化程度得到促进，而在相界阶段受到限制，并且由于CS的加入，水化反应中的扩散阶段提前。根据这些结果和分析，含CS和不含CS的CAC水化过程的差异可归因于SiO₂纳米颗粒的分布和成核作用。
