基于SEM-DIC耦合方法的混凝土界面过渡区孔隙率影响研究

Study on the Influence of Porosity in Concrete Interface Transition Zone Based on SEM and DIC Methods

混凝土界面过渡区(ITZ)是混凝土骨料与砂浆的交界区域,相比于砂浆,其具有更小的强度与弹性模量,难以直接观察测量.为了描述ITZ的损伤演化,通过原位加载压缩试验,结合扫描电镜获取特定试件的表面细观形貌,用数字图像相关(DIC)方法分析ITZ孔隙率信息并表征ITZ损伤.同时,根据孔隙等效模型进行有限元模拟,给出一种能直观表征混凝土ITZ损伤的方法.研究结果表明:ITZ损伤分布大致表现为骨料-ITZ边界处的快速增长以及ITZ-砂浆边界处的缓慢减小;ITZ的弹性模量与孔隙率之间呈负二次幂函数关系,大致上符合EMF理论;ITZ的损伤因子与孔隙率之间呈二次多项式函数关系;ITZ的损伤程度可由孔隙率来表征;考虑混凝土界面过渡区影响的有限元模拟结果与试验结果基本吻合,说明试验所得结论可靠,可为混凝土结构损伤演化提供部分理论参考与数据支持.

The concrete interface transition zone(ITZ)is the junction area between concrete aggregate and mortar.Compared with mortar,it has smaller strength and elastic modulus,so it is difficult to directly observe and measure.In order to describe the damage evolution of ITZ,in situ loading compression tests combined with scanning electron microscopy were conducted to obtain the surface microscopic morphology of specific specimens,and digital image correlation(DIC)method was used to analyze ITZ porosity information and characterize ITZ damage.At the same time,the finite element simulation was carried out according to the pore equivalent model,and a method that could intuitively characterize the ITZ damage of concrete was given.The research results show that the damage distribution of ITZ is generally characterized by rapid growth at the aggregate-ITZ boundary and slow decrease at the ITZ-mortar boundary.The relationship between the elastic modulus and porosity of ITZ is a negative quadratic power function,which is roughly consistent with EMF theory.The damage factor and the porosity of ITZ have a quadratic polynomial function relationship.The damage degree of ITZ can be characterized by the porosity.The finite element simulation results considering the influence of the concrete interface transition zone are basically consistent with the test results,indicating that the conclusions obtained from the test are reliable and can provide some theoretical reference and data support for the damage evolution of concrete structures.