基于CT技术的混凝土孔隙结构冻融损伤试验

Experiments on the freeze-thaw damage of concrete porous structure based on CT technique

运用电子计算机断层扫描(CT)技术对经历冻融循环后的混凝土试样细观损伤过程进行实时扫描,获得二维断层扫描图像。在此基础上,运用图像处理技术对孔隙结构进行三维重建,得到不同冻融循环次数下试样内部孔隙结构的空间分布特征与演化规律,以此分析孔隙结构与单轴抗压强度之间的关系。运用分形理论对冻融环境下试样孔隙结构与冻融循环次数的关系进行定量化描述。研究结果表明:试样内部孔隙的结构分布特征和演化规律与其力学性质和宏观破损特征密切相关。在冻融循环作用下,混凝土孔隙率随冻融循环次数的增加而逐渐增大,并与单轴抗压强度呈负相关;混凝土试样孔隙盒维数呈现初期降低后期增加的变化规律,即在孔隙结构的扩展经历了复杂无序—单一有序—复杂无序的演化过程。

The computed tomography （CT） technology was used to quantitatively scan the evolution of the concretedamage process under freeze-thaw cycles, and the batch of 2D slice images was obtained. Based on CT technology,the3D porous structure of concrete was reconstructed by full digital image processing analysis. The spatial distributioncharacteristics and evolution law of 3D porous structure were obtained. The relationships between porosity and uniaxialcompressive strength were analyzed. And the relationships between the porous structure and the freeze-thaw cycles weredescribed quantitatively by the fractal theory. The results show that the pore distribution of concrete material hasimportant effect on concrete mechanical property and macro damage characteristics. The volume porosity decreases withthe increase of freeze-thaw cycles and there is a negative correlation between the uniaxial compressive strength andporosity. The fractal dimension of the pore structure presents “down-up” trend with the increase of the number offreeze-thaw cycles. The porous structure evolution is changed from chaos to order and then to a process of disorder.