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A comparison of the influence of micro- and nano-silica on hydration kinetics of Portland cement under different temperatures

机译：微米和纳米二氧化硅对不同温度下港口水泥水合动力学影响的比较

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Exothermic characteristics of Portland cement incorporating 1%wt micro- and nano-silica were researched by measuring the heat releases at different testing conditions. The presence of nano-SiO2 reduces the induction period, and this effect changes with temperature. The rising temperature makes silica fume generate more significant influence on the induction period. The maximal heat release rate is influenced slightly at normal temperature and decreased to some extent at elevated temperatures through replacing 1%wt cement by micro- and nano-silica. The effects of nano-SiO2 and silica fume at 60 degrees C are almost completely consistent with each other within 7 h of hydration including induction state, acceleration state and deceleration state. Silica fume presents the property of nano-SiO2 at high temperatures, which can also be observed by analyzing their cementitious indexes. The reaction kinetics of cement with nano-SiO2 and silica fume was analyzed by the classical Krstulovic-Dabic model. The analysis results indicate that nano-SiO2 and silica fume can improve the hydration degrees (alpha(1) and alpha(2)) of the transformation from nucleation and crystal growth (NG) process to phase boundary reaction (I) process or I process to diffusion (D) process only at 60 degrees C. Nano-SiO2 can improve the phase boundary reaction at 50 degrees C and 60 degrees C judging by the difference between alpha(1) and alpha(2). The possible mechanism of nano-SiO2 and silica fume influencing the hydration kinetics was also proposed. (C) 2020 Elsevier Ltd. All rights reserved.
机译：通过在不同的测试条件下测量热释放，研究了包含1％WT微型和纳米二氧化硅的波特兰水泥的放热特性。纳米SiO2的存在降低了诱导期，并且这种效果随温度而变化。上升温度使二氧化硅烟雾产生对诱导期的影响更大。最大热释放速率在常温下略微影响，并通过微量和纳米二氧化硅取代1％wt水泥，在一定程度上减少到一定程度上。纳米SiO2和二氧化硅烟雾在60℃下的效果在包括诱导状态，加速状态和减速度状态的30℃内彼此完全一致。二氧化硅烟气在高温下呈现纳米SiO 2的性质，也可以通过分析它们的水泥指标来观察。典型的Krstulovic-Dabic模型分析了用纳米SiO2和硅粉的水泥的反应动力学。分析结果表明，纳米SiO 2和二氧化硅烟雾可以改善从成核和晶体生长（Ng）过程的转化的水合度（α（1）和α（2）），以相位边界反应（i）工艺或我的过程仅在60℃下扩散（d）过程，纳米SiO 2可以通过α（1）和α（2）之间的差异来改善50℃和60℃的相位边界反应。还提出了影响水合动力学的纳米SiO2和二氧化硅烟雾的可能机制。 （c）2020 elestvier有限公司保留所有权利。

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