单轴压缩条件下混凝土细观损伤演化机理的CT试验研究

Experimental Study of Concrete Meso-Damage Evolution Mechanism Based on Uniaxial Compression CT Method

混凝土是一种非均质的材料,在细观层次上将混凝土看作由骨料、砂浆和两者之间的界面组成的三相复合材料。本文在对混凝土进行单轴压缩试验的基础上,根据CT扫描图像反映的细观破损过程,分析了基于CT数平均值变化规律的特点;将混凝土材料的损伤过程进行了分段,提出了损伤变量的提取方法。随后结合试验得到的宏观应力应变曲线,经过拟合得到损伤变量与宏观应变的关系公式,建立了新的分段损伤演化方程及损伤本构模型。通过对比分析,验证了损伤变量的计算结果和试验结果整体吻合较好。以此深入研究了混凝土材料细观破损机理。

Concrete is a heterogeneous material and may be considered as a three-phase composite consisting of aggregate,mortar and interface between aggregate and mortar from a mesoscopic view.The variation characteristics of CT average number were analyzed by CT scan images of meso-damage process,based on CT testing of concrete meso-damage evolution under unaxial compression.Concrete damage process may be divided into several stages,and the method of extracting the damage variable was proposed.Considering the experimentally obtained macro stress-strain curve,the relation between the damage variable and macro strain was obtained by data fitting.A new equation of damage evolution damage and a damage constitutive model were established.Through comparing and analyzing,the obtained theory results coincide well with the experimental results.So the concrete meso damage-fracture mechanism was deeply investigated.