Meso-scale corrosion expansion cracking of ribbed reinforced concrete based on a 3D random aggregate model

Abstract

In reinforced concrete structures, corrosion of the rebar produces 2–6 times more corrosion product than the original material, creating pressure on the surrounding concrete, leading to cracking. The study of corrosion and cracking in reinforced concrete structures is therefore of great importance for enhancing the durability of concrete. Unlike many previous studies, we used ribbed rebar similar to that used commercially and considered the mechanical behavior of the interface transition zone (ITZ) between the aggregate and mortar to simulate the processes of corrosion and cracking of reinforced concrete structures. We explored the failure mode of the interface layer under uniform corrosion and the influence of different factors on the corrosion expansion cracking and the shedding mode of a concrete cover. This was achieved by establishing a three-phase meso-scale model of concrete based on secondary development of ABAQUS, simulating the mechanical behavior of the ITZ using a cohesive element, and establishing a rust expansion cracking model for single and multiple rebars. The results showed that: (1) Under uniform rust expansion, concrete cracks are distributed in a cross pattern with a slightly shorter lower limb. (2) When the corrosion rate is low, the ITZ is not damaged. With an increase in the corrosion rate, the proportion of elements with tensile damage in the ITZ first increases and then decreases. (3) In the case of a single rebar, the larger the cover thickness, the higher the corrosion rate corresponding to ITZ failure, and the arrangement of the rebar has little influence on the ITZ failure mode. (4) In the case of multiple rebars, the concrete cover cracks when the rebar spacing is small, and wedge-shaped spalling occurs when the spacing is large.

Abstract

目的

钢筋混凝土结构中, 钢筋锈蚀会产生2~6倍于自身的锈蚀产物, 对周围混凝土产生压力进而导致混凝土开裂。因此研究钢筋混凝土结构锈胀开裂对提升其耐久性具有重要意义。本文旨在研究钢筋混凝土锈胀开裂过程, 并探究均匀锈蚀下不同因素对锈胀裂缝形态和保护层脱落模式的影响。

创新点

1. 采用更接近实际的带肋钢筋;2. 考虑骨料与砂浆间界面过渡区(ITZ)的力学行为;3. 提出一种基于椭球体生成的单个不规则十二面体骨料及相应骨料库的生成、投放思路, 并在此基础上对ABAQUS进行二次开发, 构建一种基于已划分网格的直接生成三维实体的细观模型建立方法。

方法

1. 通过ABAQUS的二次开发建立骨料库的生成及投放方法;2. 通过ABAQUS的二次开发, 采用Cohesive单元模拟ITZ的力学行为;3. 通过上述方法构建单根及多根钢筋情况下的锈胀开裂模型;4. 通过不同钢筋横截面布置方式及保护层厚度的多组工况的仿真模拟, 分析单根钢筋及多根钢筋情况下布置方式及保护层厚度对锈胀裂缝形态的影响。

结论

1. 匀性锈胀下混凝土裂缝呈下方稍短的“十”字形分布。2. 锈蚀率较小时, ITZ不发生破坏;随着锈蚀率的增大, ITZ以拉伸破坏为主的单元占比出现先上升、后下降、再上升、最后趋于稳定的现象。3. 单根钢筋情况下, 保护层越大, ITZ开始产生破坏对应的锈蚀率越大;钢筋布置形式对ITZ破坏模式影响较小。4. 多根钢筋情况下, 钢筋间距较小时混凝土保护层发生层裂破坏, 间距较大时发生楔形剥落。