基于真实细观模型的再生混凝土破坏数值研究

Numerical Study on Damage Process of Recycled Aggregate Concrete by Real Meso-scale Model

在细观层次上视再生混凝土为非均匀六相复合材料,综合数字图像处理技术、几何矢量转换技术与有限元网格自动生成方法,提出了再生混凝土的细观有限元分析方法.根据再生混凝土各相材料的力学特性,利用自动动态增量非线性分析软件对单轴拉伸、单轴压缩作用下再生混凝土试件的细观损伤过程及宏观力学性能进行了模拟分析.在验证了所建立再生混凝土真实细观模型合理性的基础上,通过变参数分析,讨论不同天然骨料、界面过渡区和新老硬化砂浆的力学性能对再生混凝土宏观力学性能的影响.结果表明:真实骨料细观模型能更真实地模拟再生混凝土在荷载作用下的损伤破坏过程,其模拟结果与试验结果吻合较好;天然骨料力学特性对再生混凝土的破坏过程和破损路径有较大影响,天然骨料弹性模量越大,应力集中现象越明显;再生混凝土强度随新砂浆强度增大而增大,老砂浆力学性能对再生混凝土宏观力学性能的影响弱于新砂浆;再生混凝土的界面过渡区处存在拉应力和剪应力集中现象.

The recycled aggregate concrete（RAC） was taken as inhomogeneous six-phase composite. The meso finite element method for RAC was applied by incorporating digital image processing procedure, ge- ometry vectorization algorithm and automatic finite element mesh generation technique. The automatic dy- namic incremental nonlinear analysis was used to numerically simulate propagation process of cracks fracture configuration and macro-mechanical property of RAC specimen under uniaxial tension/compression based on mechanical property of each phase in RAC. On the basis of verified accuracy and reliability of the established real meso-scale model, a parametric analysis was conducted to investigate sensitivity of macro- mechanical property of RAC, which focused on different mechanical parameters of natural aggregate, in- terfacial transition zone（ITZ） and new/old hardened mortar. Numerical results indicate that the real ag- gregate model is more reliable to simulate damage process of RAC under external load, and simulation results are in a good agreement with test data. Natural aggregate has tremendous influence on failure process and damage path. Elastic modulus of natural aggregate is oversized, stress concentration phenomenon is e- ven more obvious. Strength of RAC increases along with strength of new hardened mortar, whereas old hardened mortar has little effect on macroscopic mechanical property of RAC. Concentration of tensile stress and shear stress occur in new and old ITZs.