In earlier work, we have observed discrepancies relating to the early hydration of calcium aluminate cement (CAC) when comparing data from heat flow calorimetry of CAC paste with results from mortar strength tests using the crushing method. Here, we investigated on this phenomenon and found that the sand which is used as a filler exerts a major influence on CAC hydration resulting in acceleration. Furthermore, in particular fine filler materials such as, for example, microsilica, fine limestone powder, and especially α‐ and γ‐Al₂O₃ also produced a strong hydration accelerating effect which is dependent on their specific surface area. The mechanism underlying the acceleration is that under alkaline conditions their negative surface charge attracts calcium ions as was confirmed via inductively coupled plasma atomic emission measurements. Such a layer generates favourable conditions for the nucleation of CAC hydration products (C‐A‐H phases). The resulting crystalline hydrates which form on the surface of the filler particles submerged in CAC cement pore solution were visualized via SEM imaging. This way, specifically selected fillers can significantly accelerate CAC hydration and save precious lithium salts which are commonly used to boost the early strength of CAC.

中文翻译：

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砂和填料对铝酸钙水泥水化行为的影响

在较早的工作中，我们比较了CAC浆的热流热分析数据和使用压碎法进行的砂浆强度测试的结果时，发现了与铝酸钙水泥（CAC）的早期水化有关的差异。在这里，我们对这种现象进行了调查，发现用作填充剂的沙子对CAC水化产生了主要影响，从而加速了作用。此外，特别地细填料材料，如，例如，微硅粉，细石灰石粉，特别是α-和γ-Al系₂ ö ₃还产生了强大的水合促进作用，这取决于它们的比表面积。加速的基本机理是，在碱性条件下，其负表面电荷吸引了钙离子，这已通过电感耦合等离子体原子发射测量得到了证实。这样的层为CAC水合产物的成核（C-A-H相）创造了有利条件。通过SEM成像观察形成在浸没在CAC水泥孔隙溶液中的填料颗粒表面上的所得结晶水合物。这样，专门选择的填料可以显着加速CAC的水合作用并节省通常用于提高CAC早期强度的宝贵锂盐。