SGER-Nanoscale Study of Cement Hydration by Nuclear Resonant Reaction Analysis

核共振反应分析在水泥水化的纳米尺度研究中的应用核共振反应分析已被应用于水泥水化的研究。通过使用这一技术，可以研究在感应期内氢浓度在几纳米尺度(相当于几个单位电池)上的变化作为时间的函数。初步结果表明，根据观测到的氢浓度的绝对值和测量的表面层厚度，在诱导期形成的硅酸三钙颗粒表面层与类托贝莫来石材料一致。使用非常窄的核共振反应(在这种情况下是6.4 MeV的1H(15 N？)12 C反应)，当与具有良好能量分辨率的氮离子束进行时，能够测量薄层的氢浓度。最佳束流能量分辨率是一个关键参数，因为测量的空间分辨率在很大程度上取决于入射离子束的能量分辨率。因此，德国波鸿鲁尔大学的Dynamitron串列加速器被用于实验研究，因为这台机器在过去15年里进行了广泛的工作，以产生尽可能好的离子束能量分辨率。通过提高束流能量，可以逐步研究更深的层。因此，通过使用来自6.4 MeV共振的连续较高能量的氮束，可以确定水化过程中氢浓度随时间的分布。氢浓度是在颗粒表面的几个纳米深度上获得的，并且可以连续测量到颗粒中大约2微米的深度。对硅酸三钙在20℃下的水化过程进行了研究，测得诱导时间为4.25小时，统计精度为0.07小时。与温度相关的结果得到Arrhenius图的屈服和活化能为69kJ/mol。

Nanoscale Investigation of Cement Hydration by Nuclear Resonant Reaction Analysis Nuclear Resonant Reaction Analysis (NRRA) has been applied to study cement hydration. Through the use of this technique, the change in hydrogen concentration on a few nanometer scale (corresponding to a few unit cells) can be studied as a function of time during the induction period. Initial results have demonstrated that the surface layer formed during the induction period on the tricalcium silicate grains (used in this study) is consistent with a tobermorite-like material, based on the absolute value of the observed hydrogen concentration and the measured thickness of the surface layer. The use of a very narrow nuclear resonant reaction (in this case the 1 H (15 N?) 12 Creaction at 6.4 MeV), when performed with a beam of nitrogen ions that has excellent energy resolution, is capable of measuring the hydrogen concentration of a thin layer. Optimum beam energy resolution is a critical parameter as the spatial resolution of the measurement is defined largely by the energy resolution of the incident ion beam. Therefore, the Dynamitron Tandem accelerator at the Ruhr Universitat, Bochum, Germany is being used for the experimental studies as this machine has had extensive work done over the last fifteen years to generate the best possible energy resolution for ion beams. By raising the beam energy, progressively deeper layers can be investigated. Thus, by using nitrogen beams of successively higher energies from the 6.4 MeV resonance, a profile of the hydrogen concentration as a function of time in the hydration process can be determined. The hydrogen concentration is obtained over a depth of a few nanometers at the surface of the grains and can be measured continuously to a depth of about 2 microns into the grains. A study of the hydration process of tricalcium silicate at 20 o C determined an induction time of 4.25 hours with a statistical precision of 0.07 hours. Temperature dependent results form an Arrhenius plot yielding and activation energy of 69 kJ/mol.