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

摘要：该项目是缅因州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3D微结构成像与离散元素计算建模的融合，以解决显著微结构特性与散体材料性能之间的定量联系的需求。材料微观结构的高分辨率3D图像将使用X射线显微层析成像(XMT)来产生。这些图像将被用来检验水泥复合材料对机械载荷和干燥收缩的微观机械响应。在选定的加载阶段，将测量三维变形场和内部裂纹分布，并将其与夹杂物的空间分布和水泥浆体孔隙率的局部变化相关联。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。计算模型将基于从3D图像数据确定的微结构特征的显式表示。虽然大多数测量和分析将在微米到厘米的尺度上进行，但结果将被解释为模拟实际系统所必需的几个关键长度尺度之一。该项目的成果将有助于在细骨料和中孔可被视为离散实体的尺度上理解混凝土断裂。对于这种情况，目前几乎没有定量的工作。对这种规模的裂缝细节的了解对于改善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中的混凝土结构的使用寿命所做的努力。这项拟议的工作符合向材料建模的形态基础的范式转变。因此，拟议的工作与更广泛的材料类别有关，而不仅仅是水泥和混凝土复合材料。

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.