广州地区城市地下混凝土结构临界氯离子含量研究

陈晓斌^{1, 2}，唐孟雄²，胡贺松²，马昆林¹

(1. 中南大学 土木工程学院，湖南 长沙，410075；
2. 广州市建筑科学研究院，广东 广州，510440)

摘 要：主要针对广州地下混凝土结构侵蚀环境特点，进行氯离子侵蚀的快速腐蚀模拟实验。实验研究表明：较小的水与灰质量比和适量粉煤灰的掺入增加混凝土氯离子吸附能力，较大的保护层厚度、较小的水与灰质量比和掺粉煤灰降低混凝土的电流强度和延长电流稳定时间。同时微观结构分析显示氯盐腐蚀造成钢筋表层混凝土膨胀，结构出现膨胀劣化。通过氯离子侵蚀下锈蚀模拟实验与工程调查验证分析，推荐广州地区城市地下混凝土结构受氯离子侵蚀钢筋表面临界氯离子含量为0.04%~0.05%(质量分数)，该值考虑混凝土对氯离子的结合及吸附的影响，为地区地下混凝土结构氯离子侵蚀寿命预测提供了参考。

关键词：城市地下结构；混凝土；氯离子；结构耐久性；微观结构

Chloride ion threshold for underground structure durability estimation exposured to chloride ions invading in Guangzhou

CHEN Xiao-bin^{1, 2}, TANG Meng-xiong², HU He-song², MA Kun-lin¹

(1. School of Civil Engineering, Central South University, Changsha 410075, China;
2. Guangzhou Institute of Building Science, Guangzhou 510440, China)

Abstract:According to the chloride invading environment’s properties in Guangzhou underground, a series of enforcement concrete rebar’s rapid rusting stimulation tests exposed to chloride invading were conducted. The results show that the chloride iron adsorption capacity of concrete is obviously improved by lower water binder ratio and flash air mixing. At the same time, the electric current’s stability is enhanced under the bigger cover thickness, lower water binder ratio and flash air mixing during the rapid corrosion tests. The microstructure analysis shows that there are lots of Friede salt and Ettringite(Aft) crystallization inside specimens, which cause concrete loose internal structure and mechanical deterioration. A critical chloride ion content of 0.04%-0.05% (mass fraction) for urban underground structure durability assessment is recommended through rapid corrosion simulation tests and practical validation analysis, considering which the physical and chemical chloride bonding adsorption. The recommended critical chloride ion content presents a rebar rusting standard for the urban underground structure service prediction exposed to chloride invading.

Key words:urban underground structure; concrete; chloride ion; durability of structure; microstructure