Nanoscale Determination of Cement and Concrete Hydration by Nuclear Resonant Analysis

纳米级水泥和混凝土水化的核共振分析(NRRA)--以6.4 MeV的15N(H，a)12C反应为基础，研究了诱导期的水泥水化。在诱导期期间和之后，可以研究氢浓度在几纳米尺度(大约一个单位电池)上作为深度和时间的函数的变化。通过将光束能量提高到共振能量以上，可以测量到几微米的深度，相当于水泥颗粒的半径。因此，颗粒中的完全水化过程被确定为深度的函数。结果表明，诱导期在C3S颗粒表面形成的表面层与托贝莫来石相一致。了解水泥水化的细节最终将是确定从微观性质到宏观性质转变的基础。硅酸三钙在20℃时的诱导期为4.25小时，统计精度为0.07小时。在10℃和30℃下测得Arrhenius图的活化能为69.4kJ/mol。随后，我们的工作开始深入了解其他水泥组分以及促进剂和缓凝剂的影响。最近，我们开始研究铝酸钙的水化过程以及常用缓凝剂葡萄糖酸钠的影响，并开始分析混凝土的成分，以了解它们与水泥的相互作用。这项建议支持使用NRRA技术对水泥水化进行详细研究。具体的实验将考察缓凝剂和促进剂的影响。这项工作将与我们在W.R.格雷斯的行业合作伙伴一起完成，他们将贡献他们在该领域的专业知识和分析能力。从它们用于确定作为缓凝剂和促进剂的材料添加剂的工业技术开始，我们将对它们进行修改，以确定确定水化行为的基本物理参数。这些将与Grace可以提供的分析测量相结合，以开发水化行为的理论模型。实验数据清楚地揭示了不同的参数，如温度、pH和起始成分，是如何影响水化过程的。这些信息最终将被用来改进用于建筑和其他目的的水泥和混凝土的配方。除了对参与该项目的学生(通常是美国、德国和西班牙之间的4-6人)进行教育外，还将在大学和科学会议上进行重要的演讲。作为进行这种实验的唯一小组，我们已经开始在国际会议上展示结果，并开始与更多亚洲和欧洲国家的研究人员合作，研究混凝土水化的更多方面。

GOALI- Nanoscale Determination of Cement and Concrete Hydration by Nuclear Resonant AnalysisNuclear Resonant Reaction Analysis (NRRA) with the 15N(H,a) 12C reaction at 6.4 MeV has been applied to study cement hydration during the induction period. The change in hydrogen concentration on a few nanometer scale (roughly a unit cell) as a function of depth and time can be studied during and immediately after the induction period. By raising the beam energy above the resonance energy, measurements are made to depths of a few microns, comparable to the cement grain radius. Thus, the complete hydration process in the grains is determined as a function of depth. Results have shown that the surface layer formed during the induction period on C3S grains is consistent with a tobermorite-like material. Understanding the details of the hydration of cement will ultimately be the base for defining the transition from microscopic to macroscopic properties. The induction period of tricalcium silicate at 20 oC was 4.25 hours with a statistical precision of 0.07 hours. With measurements at 10 and 30 oC an Arrhenius plot yielded an activation energy of 69 4 kJ/mol. Subsequently, our work has begun to yield insight into other cement components and the effects of accelerators and retarders. Recently, we have begun to study the hydration of calcium aluminate and the effects of sodium gluconate, a commonly used retarder and have started to analyze components of concrete to understand their interaction with the cement. This proposal supports a detailed investigation of cement hydration, by using the NRRA technique. Specific experiments will investigate the effects of retarders and accelerators. This work will be performed with our industrial collaborators at W. R. Grace who will contribute their expertise and analytical capabilities in this area. Starting with their industrial techniques for determining material additives as retarders and accelerators, we will modify them to determine the underlying physical parameters to determine hydration behavior. These will be combined with analytical measurements that Grace can provide to develop theoretical models of hydration behavior. The experimental data provides clear insights into how different parameters, temperature, pH, and starting composition, affect the hydration process. This information will ultimately be used to improve the formulation of cements and concrete for construction and other purposes.In addition to the education of students working on this project (typically 4-6 between the US, Germany and Spain), significant presentations are given at universities and scientific meetings. As the only group performing such experiments, we have begun to present results at international conferences and have begun working with researchers in even more countries in Asia and Europe on more aspects of concrete hydration.