关键词: 大坝, 混凝土, 耐久性, 微观结构

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