Corrosion damage characteristics of steel bars through new-old concrete interfacial zone connected by pre-compression

Abstract

Pre-compression connections are widely used in precast concrete structures. In order to reveal the corrosion characteristics of steel bars through the interfacial zone of new-old concrete, the corroded steel bars through the interfacial zone were obtained by long-term exposure tests in two stages of chloride solution wet-dry cycles and then natural corrosion. Then, three-dimensional (3D) laser scanning, finite element tensile simulation, and physical tensile test were carried out to study the influence of different eroding durations and pre-compression stress on the corrosion morphology and mechanical properties degradation of steel bars through the interfacial zone. The results show that the steel bars through the interfacial zone of all specimens present a typical local pitting corrosion morphology, and the corrosion degree is significantly higher than that in the non-interfacial zone (the cross-sectional corrosion loss rate in the interfacial zone is 1.5–4 times higher than that of old concrete and 3–6 times higher than that of new concrete), which reflects the obvious “interfacial zone effect (IZE)” and strain concentration effect (the largest strain concentration factor at the pit of interfacial zone is high to 59.8). The static tensile properties of the specimens with the interfacial zone were degraded comprehensively, especially the degradation of the ultimate tensile strain was the most significant (for the most severely degraded specimens, the ultimate strain degraded by 76%). In general, the increase in eroding duration and the presence of pre-compression stress weakens the IZE. As the strain concentration effect increases, the yield strength, ultimate strength, and ultimate strain decrease approximately linearly. It can be seen that the existence of the interfacial zone will lead to serious local pitting corrosion of the steel bars in it, which is the key problem of the durability degradation of the precast concrete structures.