Abstract: The concrete core samples from four typical locations of a hydropower station that has been in service for sixty years were selected to carry out the study. The compressive strength, impermeability and frost resistance of the concrete core samples were tested according to the specifications. The hydra - tion products, microstructure, porosity and pore size distribution of the concrete core samples were test - ed by the X-ray diffractometer (XRD), scanning electron microscope (SEM) and low-field nuclear magnetic resonance. Moreover, based on the porosity and pore size distribution, the relationship between them and strength was explored. The results showed that the internal carbonization of the concrete core sam- ples was obvious, but the matrix was intact, and the bonding between the aggregates and the hardened paste was good. The results of low-field nuclear magnetic resonance indicated that the porosity of the concrete core sample was between 4.56%~8.40%, and the pore size was basically distributed between 1~ 200 nm. The lower the porosity of the core sample meant the higher the compressive strength and the higher the anti-permeability level. However, the correlation between porosity and frost resistance grade was poor. Compared with the porosity, the proportion of pores between 20~ 100 nm had a better correla- tion with the strength of the concrete core sample, and the correlation coefficient reached 0.954.

Key words: dam concrete, core strength, pore structure, microscopic product

摘要： 选取某服役60 多年水电站4 个典型位置的混凝土芯样，依据规范测试混凝土芯样的抗压强度、抗渗性及抗冻性，采用X 射线衍射仪（XRD）、扫描电子显微镜（SEM）及低场核磁对混凝土芯样的水化产物、微观结构、孔隙率及孔径分布进行测试，并根据孔隙率以及孔径分布探究其与强度之间的关系。结果表明，混凝土芯样内部碳化现象较为明显，但是基体完整，骨料与硬化浆体之间粘结良好。低场核磁结果表明混凝土芯样的孔隙率在4.56%~8.40%，孔径基本分布在 1~200 nm 。芯样的孔隙率越低，抗压强度越高，抗渗等级越高，但孔隙率与抗冻等级的相关性较差。相较于总孔隙率，20~ 100 nm 孔的比例与混凝土芯样的强度相关性更好，相关系数可达到0.954。

关键词: 大坝混凝土, 芯样强度, 孔结构, 微观产物