除冰盐环境下水泥混凝土路面传力杆的锈蚀机理与传荷失效过程分析

传力杆锈蚀所引起的混凝土保护层开裂是影响水泥混凝土路面结构使用寿命的重要因素。该文基于扩展有限元方法，建立了传力杆锈蚀产物-混凝土保护层耦合作用开裂力学分析模型。使用此模型模拟了混凝土保护层锈胀开裂过程中的弥散分布裂纹起裂及扩展演化行为，研究了除冰盐环境下传力杆因锈蚀引起传荷失效的过程。设计传力杆试件的除冰盐环境室外暴露试验对数值模拟结果进行验证，发现两者在锈胀开裂模式方面符合较好。根据已验证的模型分析发现:传力杆的松动是促使其快速脱钝，并发生严重锈蚀的初始条件，松动量对传力杆表面锈蚀产物的物相组成比例无明显影响；锈蚀产物体积膨胀造成混凝土保护层出现龟裂，降低了混凝土为传力杆提供支承的能力，是传力杆因锈蚀导致传荷失效的主要原因。

ANALYSIS OF CORROSION MECHANISM AND DETERIORATION PROCESS FOR DOWEL UNDER DE-ICING SALT ENVIRONMENT

Cracking in concrete protective layer due to dowel bar corrosion is one of the important influence factors for the durability of cement concrete pavement structure. Based on the eXtended finite element method, a fracture theory model, which can consider the coupling effects of corrosion product and concrete protective layer fracture, was established and verified in this paper. The initialization and growth of smeared cracks in concrete protective layer were simulated. Then the numerical results were employed to investigate the dowel bar deterioration reason due to corrosion expansion. It has shown that the numerically predicted crack mode agrees well with the in-situation experimental results in de-icing salt environment. The numerical results based on the verified model demonstrate that the dowel looseness accounts for the main reason about steel depassivation and heavily corroded, but it has no significant effect on corrosion product. It can also be concluded that the significant reason of deterioration of dowel bar is the crack formation in concrete protection layer caused by corrosion product volume expanding.