This work studied the effect of metakaolin fineness on the performances of cement-based materials through measurements of calorimetric response, mechanical properties, and capillary water absorption. Using multi-technique characterization (X-ray diffraction, SEM, TGA, MIP, and solid state 29Si NMR), the phase composition and microstructural characteristics of samples were analyzed. Results indicate that the presence of metakaolin accelerates the hydration of cement, and the acceleration effect is more significant with the finer MK. Increased MK fineness enhances its pozzolanic reactivity at early age. Fine metakaolin significantly enhances the mechanical properties of cement mortars compared to coarse metakaolin. Finer metakaolin reduces both initial and secondary water absorption rates, with optimal effects observed at 20 % replacement. The incorporation of metakaolin refines the ITZ and the cement matrix, these effects are more pronounced with increasing fineness. However, 29Si NMR results suggest an optimal fineness below which further benefits do not increase.

中文翻译：

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偏高岭土细度对水泥基材料性能和微观结构的影响


这项工作通过测量量热响应、机械性能和毛细管吸水率，研究了偏高岭土细度对水泥基材料性能的影响。使用多种技术表征 （X 射线衍射、SEM、TGA、MIP 和固态 29Si NMR），分析了样品的物相组成和微观结构特征。结果表明，偏高岭土的存在加速了水泥的水化，且加速效应越细，加速效应越细，MK细度越高，其火山灰反应性越强。与粗高高岭土相比，细高高岭土显着增强了水泥砂浆的机械性能。更细的偏高岭土可降低初始和二次吸水率，在 20% 的替代率下观察到最佳效果。偏高岭土的掺入细化了 ITZ 和水泥基质，这些效果随着细度的增加而更加明显。然而，29Si NMR 结果表明最佳细度，低于该细度后，进一步的好处不会增加。