Growth and porosity of C-S-H phases, development of the `Sheet Growth Model` and coupling with experimental data (1H NMR, SEM)

了解水泥水化的主要产物--硅酸钙(C、S、H)的微观结构和形成过程是了解混凝土性能的关键。改进的实验证据和高分辨率建模的并行发展使得能够模拟结构变化并评估其对混凝土宏观性能(收缩、强度、耐久性等)的影响。在该项目的前一部分，基础知识的界限可以大大推进。用高分辨扫描电子显微镜、核磁共振氢谱、X射线衍射仪和压汞测孔仪对C-S H相的形成进行了分析。这些实验结果被用来进一步发展微结构的“片状生长”模型，并调整模型参数。这种方法使我们能够模拟C-S H相的生长过程，这种生长过程与微观结构(扫描电子显微镜、核磁共振)非常相似，范围从0.5到500 nm。在扩展项目中，建模将建立在项目前一部分奠定的坚实基础上。我们的模型将扩展到其他未水化相(阿利特和贝利特)和水化相(内C S H，外C-S-H，CH)。进一步，我们将调整水合物的形态和密度以适应真实的结构，并显着扩大模型的区域。这是通过将“资产负债表增长”模型与“水平集”方法相结合来实现的。水平集方法能够模拟随时间变化的多阶段变化。我们将使用组合模型来描述从0.5 nm到1000微米的三维尺度上的气孔、结构和空间相分布的发展。为了完成这项研究，将验证模型的输出，并将使用以下实验数据进一步校准参数。使用X射线和聚焦离子束(FIB)的扫描电子显微镜(SEM)进行的纳米层析成像研究将三维和时间相关地描述相的孔隙率和体积发展。将这些技术与1H-核磁共振波谱和对湿样品和干样品的低温差示扫描量热仪相结合，将使我们能够评估完整尺度下的孔径分布的发展以及毛细和较大孔隙的含水饱和度。此数据直接用于使建模逼真。在未来，用这种方法得到的模型可以预测混凝土的特性值(收缩、徐变、渗透性)。

Understanding the micro-structure and process of formation of Calcium-Silicate-Hydrates (C S H) which are the main products of cement hydration is the key to understand properties and performance of concretes. Improved experimental evidence and parallel development of high resolution modelling allows simulating structural changes and to assess their impacts on macroscopic properties of concrete (shrinkage, strength, durability etc.). During the preceding part of the project the boundaries of fundamental knowledge could be pushed forward significantly. The formation of C S H phases were analysed by high-resolution scanning electron microscopic (SEM) investigations, proton nuclear magnetic resonance spectroscopy (1H-NMR), X ray diffraction analysis (XRD) and mercury intrusion porosimetry (MIP). These experimental results were used to develop the microstructural ‘Sheet Growth’ model further and to tune model parameters. This approach enabled us to simulate the growth of C S H phases that closely resembles microstructural findings (SEM, 1H-NMR) at a scale from 0.5 to 500 nm in three dimensions. In the extended project, the modelling will be based on the strong foundation laid by the previous part of the project. Our model will be extended towards other unhydrated (alite and belite) and hydrated phases (inner C S H, outer C-S-H, CH). Further on we will adjust the morphology and density of the hydrates to real structures and significantly enlarge the modelled domain. This is achieved by combining the ‘Sheet Growth’ model with the ‘Level-Set’ approach. The ‘Level Set’ approach is able to simulate multi-phase transformations over time. We will use the combined models to describe the development of pores, structures and spatial phase distribution in a scale from 0.5 nm to 1000 µm in three dimensions. To make this study complete, the model output will be verified, and parameters will be further calibrated with the following experimental data.Nanotomography investigations using X-Rays and SEM with Focused Ion Beam (FIB) will depict porosity and volume development of the phases three dimensionally and time depended. The combination of these techniques with 1H-NMR spectroscopy and low temperature differential scanning calorimetry on wet and dried samples will allow us to evaluate the development of the pore size distribution at full scale and the water saturation of capillary and larger pores. This data is used directly to make the modelling realistic. In the future, the model obtained in this way can offer the possibility of predicting characteristic values (shrinkage, creep, permeability) of concretes.