Collaborative Research: An Integrated Microstructure-Based Approach to Property Prediction for Cement-Based Materials

摘要：该项目是缅因大学和加州大学戴维斯分校研究小组之间的合作成果。它代表了 3D 微结构成像与离散元计算建模的融合，以满足显着微结构特性和散装材料性能之间定量联系的需求。将使用 X 射线显微断层扫描 (XMT) 生成材料微观结构的高分辨率 3D 图像。这些图像将用于检查水泥复合材料对机械载荷和干燥收缩的微观机械响应。 3D 变形场和内部裂纹分布将在选定的加载阶段进行测量，并与夹杂物的空间分布和水泥浆孔隙率的局部变化相关。通过开发计算模型和适当的逆分析，我们将提供难以测量的微观机械性能的精确估计，包括水泥-骨料界面强度、桥接力和干燥收缩产生的特征应力。计算模型将基于根据 3D 图像数据确定的微观结构特征的明确表示。尽管大多数测量和分析将在微米到厘米尺度上进行，但结果将被解释为实际系统建模所需的几个关键长度尺度之一。该项目的结果将有助于理解混凝土断裂的尺度，其中细骨料和中孔可以被视为离散的实体。对于这种情况几乎没有定量的工作。了解这种规模的裂缝细节对于提高混凝土材料的性能至关重要，包括目前为延长暴露在恶劣环境下的混凝土结构的使用寿命所做的努力。所提出的工作符合材料建模形态基础的范式转变。因此，拟议的工作涉及水泥和混凝土复合材料之外的更广泛的材料类别。

Abstract: The project is a collaborative effort between the research groups at the University of Maine and the University of California, Davis. It represents a convergence of 3D micro-structural imaging with discrete element computational modeling to address the need for quantitative links between salient micro-structural properties and bulk material performance. High-resolution 3D images of material microstructure will be produced using x-ray microtomography (XMT). These images will be used to examine the micromechanical response of cement composites to mechanical loading and drying shrinkage. 3D deformation fields and internal crack distributions will be measured at selected loading stages and correlated with the spatial distribution of inclusions and local variations in cement paste porosity. Through developments of a computational model and appropriate inverse analyses, we will provide refined estimates of micromechanical properties that have been difficult to measure, including cement-aggregate interfacial strength, bridging forces, and eigen stresses produced by drying shrinkage. The computational models will be based on an explicit representation of micro-structural features, as determined from the 3D image data. Whereas most of the measurements and analyses will be conducted at the micron to centimeter scale, the results will be interpreted as one of the several critical length scales necessary for modeling practical systems. The project results will contribute to the understanding of concrete fracture at the scale in which fine aggregates and meso-pores can be viewed as discrete entities. Little quantitative work exists for this situation. Knowledge of the details of cracking at this scale is essential to improving the performance of concrete materials, including current efforts to extend the service life of concrete structures exposed to severe environments. The proposed work fits within a paradigm shift towards morphological bases for material modeling. As such, the proposed work is relevant to a wider range of material classes, beyond cement and concrete composites.