Significance of Paste-Sand Interfaces in Micromechanical Behavior of Concrete

本研究的目的是将材料科学和结构工程相结合，引入一种新的方法来研究混凝土的微观力学行为。通过对水泥浆-砂粒界面在纯单轴压缩混凝土应力-应变特性中的定性和定量意义及作用的评价。在 实验部分,砂浆缸砂的颗粒 不同的包装特点进行压力测试 - 应变行为和微机械性能。混凝土圆柱体也将进行测试，以比较粗骨料与砂粒的重要性。然后利用扫描电镜、背散射电子分析和图像分析能力、汞侵入孔隙度测定法和电导率测量技术，将这些与微观结构特性相关联。在分析部分，建立了一个描述混凝土微观力学行为的模型，定量地定义了界面参数的作用和意义。在模型开发中，采用非线性断裂力学方法，以有限元方法作为分析裂纹扩展和局部变形的工具。研究裂纹扩展与砂粒堆积特性之间的关系。在这种方法中，界面被视为弱平面或初始缺陷。这项研究的结果可以扩展到其他情况，包括耐久性、蠕变和收缩考虑，以及传统和先进水泥基混凝土复合材料的最佳混合比例。

The objective of the proposed investigation is to introduce a new approach to the study of the micromechanical behavior of concrete by combining its materials science and structural engineering aspects, based on the assessment of the qualitative and quantitative significance and role of cement paste-sand particle interfaces in stress-strain behavior of concrete that is subjected to pure uniaxial compressive force. In the experimental part, mortar cylinders having sand particles of different packing characteristics are tested for their stress- strain behavior and their micromechanical properties. Concrete cylinders will also be tested to compare the significance of the coarse aggregate with the sand particles. These are then correlated with the microstructural properties using SEM with backscatter electron analysis and image analysis capabilities, mercury intrusion porosimetry, and electrical conductivity measurement techniques. In the analytical part, a model is developed which describes the micromechanical behavior of concrete and defines quantitatively the role and significance of interfacial parameters. In the model development a nonlinear fracture mechanics approach is taken using the finite element method as a tool to analyze crack propagation and localized deformation. The relationship between crack propagation and sand particles packing characteristics will be studied. In this approach, interfaces are treated as weak planes or initial flaws. Results of this investigation can be extended to other cases including durability, creep, and shrinkage considerations, and optimum mixture proportioning of conventional and advanced cement-based concrete composites.