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

核共振反应分析（Nuclear resonance Reaction Analysis， NRRA）已被应用于水泥水化研究。通过使用该技术，可以研究诱导期间几个纳米尺度（对应于几个单位电池）上氢浓度的变化作为时间的函数。根据观测到的氢浓度绝对值和测量到的表面层厚度，初步结果表明，在诱导期形成的硅酸三钙颗粒（本研究中使用的）表面层与托贝莫里石样物质一致。使用一个非常窄的核共振反应(在这种情况下是1h （15n ?）（12）在6.4 MeV（兆电子伏特）下，用具有优异能量分辨率的氮离子束进行创造，能够测量薄层的氢浓度。最佳光束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，德国鲁尔大学的Dynamitron串联加速器被用于实验研究，因为在过去的15年里，这台机器已经做了大量的工作，以产生最好的离子束能量分辨率。通过提高光束能量，可以逐步研究更深的层。因此，通过使用来自6.4 MeV共振的连续更高能量的氮束，可以确定水化过程中氢浓度随时间的函数曲线。氢浓度可以在晶粒表面几纳米的深度上得到，并且可以连续测量到晶粒内部约2微米的深度。对硅酸三钙在20℃下的水化过程进行了研究，确定了4.25 h的诱导时间，统计精度为0.07 h。温度相关的结果形成了产率和活化能为69 kJ/mol的Arrhenius图。

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.