Abstract: The long-term service as well as safety and stability of concrete dams are closely related to the performance evolution and durability of concrete materials.In this paper,the surface defects and internal defects of long-term service concrete dams are investigated,and the microstructure and performance of concrete are studied using comprehensive thermogravimetric analysis,scanning electron micro- scope and mercury intrusion method.The results show that the leakage and dissolution are main factors cause internal defects,changes in hydration products composition,degradation of microstructure and performance for concrete dams.Dissolution leads to a decrease in the content of Ca(OH)₂in hydration products,and causes damage to growth forms accompanied by appearance of a large number of CaCO₃ particles.At the same time,dissolution will cause further deterioration of the pore structure of concrete and the increase of internal defects such as holes and looseness,which is not conducive to the overall stability of the concrete dam.Special attention should be paid to the effects of cracks,leakage and dissolution during the operation and maintenance of concrete dams.

Key words: dam, concrete, durability, microstructure

摘要： 混凝土坝长效服役安全与材料的性能演变和耐久性问题密切相关。笔者对长期服役混凝土坝的表面缺 陷和内部缺陷进行调研，并综合采用热重分析、扫描电子显微镜和压汞法等手段研究了混凝土的微观结构与性 能。结果表明：渗漏和溶蚀是导致混凝土坝出现内部缺陷、水化产物组成变化、微观结构演变和性能劣化的主要 因素。溶蚀导致水化产物中Ca(OH)₂含量减少，生长形态遭受破坏，并伴有大量的CaCO₃颗粒出现。同时，溶蚀还 导致混凝土的孔结构特性劣化，孔洞、酥松等内部缺陷增多，不利于混凝土坝整体稳定。混凝土坝运营和维护过 程中应特别注意裂缝、渗漏和溶蚀等问题的影响。

关键词: 大坝, 混凝土, 耐久性, 微观结构