基于性能演变理论的混凝土细观损伤特性研究

为研究混凝土性能演变过程中的损伤特性，借助细观力学随机骨料模型，将化学-热-力耦合的性能演变模型引入混凝土损伤特性研究中，直观反映早龄期混凝土的材料性能和损伤参数随其内部水化反应的演变过程.结合连接宏-细观热力学特性的均匀化方法，对硬化过程中混凝土三相介质的材料参数进行率定，并且在细观层次上实现早龄期混凝土单轴拉伸试验的数值模拟.结果表明，水化度的空间分布差异性对早龄期混凝土力学参数的取值存在显著影响；采用的水化度损伤模型能够直观反映早龄期混凝土试件在单轴拉伸试验中裂缝萌生、扩展直至贯通的全过程，可以为早龄期混凝土结构的拉伸损伤断裂过程分析提供有力的数值工具.

Study of meso-damage characteristics of concrete based on properties evolution theory

To study the damage characteristics in the process of properties evolution of concrete, combined with the random aggregate model, the coupled thermo-chemo-mechanical properties evolution model was introduced to study the damage characteristics of early-age concrete specimens. The evolutionary process of the material parameters and damage parameters along with the hydration process of early-age concrete could be reflected directly and explicitly by this theory. Through a homogenization method by which the thermodynamic properties of concrete were connected between macroscopic and mesoscopic level, the thermal and mechanical parameters of three-phase medium were calibrated respectively and accurately. The uniaxial tension numerical text of early-age concrete was simulated at mesoscopic level. The whole process of crack initiation, extension and penetration of the early-age concrete numerical specimens was researched in detail, as well as the damage characteristics. The simulation shows that the spatial distribution difference of hydration degree has a significant influence on the value of elastic modulus, tensile strength and other mechanical parameters of early age concrete; the whole developing process of crack can be visually exhibited by this hydration damage mode, which supplies a powerful numerical tool to the analysis of early-age concrete tensile failure.