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

该项目是缅因大学和加州大学戴维斯分校研究小组的合作成果。它代表了三维微结构成像与离散元计算建模的融合，以解决显著微结构特性和大块材料性能之间定量联系的需求。材料微观结构的高分辨率三维图像将使用x射线显微断层扫描（XMT）产生。这些图像将用于检查水泥复合材料对机械加载和干燥收缩的微观力学响应。在选定的加载阶段测量三维变形场和内部裂缝分布，并将其与包裹体的空间分布和水泥浆体孔隙度的局部变化相关联。通过计算模型的发展和适当的反向分析，我们将提供难以测量的微观力学特性的精确估计，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。计算模型将基于微观结构特征的显式表示，由3D图像数据确定。虽然大多数测量和分析将在微米到厘米尺度上进行，但结果将被解释为建模实际系统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，其中细骨料和介孔可以被视为离散的实体。针对这种情况的定量研究很少。了解这种规模的开裂细节对提高混凝土材料的性能至关重要，包括目前延长暴露在恶劣环境下的混凝土结构的使用寿命。提出的工作符合向材料建模的形态学基础的范式转变。因此，拟议的工作与水泥和混凝土复合材料以外的更广泛的材料类别相关。

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.