Influence of Fracture Surface Roughness Characteristics on the Specific Fracture Energy of Concrete as a Function of Specimen and Aggregate Size

通过研究断裂表面的粗糙度特征，如表面粗糙度指数、分形维数和波长含量，来评价微观尺度和混凝土抗压强度对单位裂缝表面积断裂能的影响。本研究的主要目标是：a)在CMOD控制下，对具有3种最大骨料粒径和3种混凝土抗压强度的3种尺寸的混凝土梁试件进行三点弯曲试验，确定断裂面的粗糙度特征，即粗糙度指数、分形维数、b)研究断裂表面的粗糙度特征，并评估其对最大骨料粒径和混凝土抗压强度的依赖，以及它们对“荷载-荷载-点-位移”响应和比断裂能的影响。C)发展基于微观力学的半经验分析，其中表观韧性将根据观察到的裂纹路径和骨料尺寸的给定粗糙度特征计算。这项研究计划将通过大学-国家-工业合作进行。研究结果将改进规范和评估普通和高强混凝土性能的方法，从而实现更有效的设计。

9713997 Perdikaris The influence of the microscale and concrete compressive strength on the fracture energy per unit crack surface area will be evaluated by studying the roughness characteristics of a fracture surface, such as the surface roughness index, fractal dimension and wavelength content. The major objectives of this research are: a) to perform 3-point bending tests under CMOD control on concrete beam specimens of three sizes with three maximum aggregate sizes and three concrete compressive strengths and determine the roughness characteristics of the fracture surfaces, that is the roughness index, fractal dimension, and Fourier amplitude spectra for each fracture surface b) to study the roughness characteristics of the fracture surfaces and to evaluate their dependence on the maximum aggregate size and concrete compressive strength and their influence on the "load vs. load-point-displacement" response and the specific fracture energy. c) to develop a micromechanics-based semi-empirical analysis, wherein the apparent toughness will be calculated based on the given roughness characteristics of the observed crack paths and aggregate size. This research program will be undertaken through a university- state-industry collaboration. The results will improve the methods of specification and evaluation of the performance of normal and high strength concrete resulting in more efficient designs.