腐蚀环境下预应力锚筋损伤试验研究

Damage tests of pre-stressed anchor bars in corrosion environment

为了深入研究腐蚀环境中锚固结构腐蚀损伤发展规律,考虑氧气浓度与局部腐蚀的影响,在室内开展腐蚀环境下预应力锚筋浸泡腐蚀试验及腐蚀试样材料力学性能试验。腐蚀试验过程中进行电化学测试与筋材局部应变监测,基于试验结果分析预应力、环境pH值、环境含氧浓度等因素与锚筋腐蚀速率、外观损伤特性、单位长度损失量、力学特性之间的关系,并探讨不同含氧环境下预应力锚筋局部应变发展规律。试验结果表明:(1)弱酸环境中酸性越强锚筋腐蚀速率越快;(2)氧气对预应力锚筋腐蚀促进作用显著,环境氧气浓度越高腐蚀速率越大,但超过一定值后增大现象不明显;(3)试验条件下,随着通氧速率增大,锚筋单位长度腐蚀量增加;(4)锚筋极限伸长率、极限抗拉载荷、弹性模量3个力学指标随着环境氧含量增大有明显的下降现象,且在同一通氧速率下,极限伸长率损失率最大,弹性模量损失率次之,而极限承载力损失率最小;(5)局部腐蚀使受腐蚀截面力心发生偏移,不同含氧环境下锚杆表面应变发展迥异,富氧侧应变呈拉应变增大趋势,而缺氧侧则由拉应变向压应变发展。

In order to study the corrosion damage of anchorage structure, the indoor accelerated corrosion tests and the mechanical tests of corroded specimens were carried out considering the effects of oxygen concentration and local corrosion. The electrochemical measurement and the local strain monitoring of reinforced material were conducted during the corrosion tests. The relationships between the pre-stresses, the environment pH values, the oxygen concentrations, the corrosion current density, the appearance damage characteristic, the corroded weight per unit length and the mechanical properties of anchor bars were analyzed based on the test results. The local strain development of the pre-stressed anchor under the different oxygen environment was also studied. The results show that the stronger the acidity is, the higher the corrosion rate in the weak acid environment. The oxygen has significant effect on the corrosion of the pre-stressed anchor and the corrosion rate increases whit the oxygen concentration increasing. However, the effects are insignificant when the concentration of oxygen exceeds a certain value. The corrosion weight per unit length increases as the oxygen supplying rate rises under the experimental conditions. The ultimate elongation, ultimate tensile load and elastic modulus decrease significantly