不锈钢钢筋锈损特征扫描分析及性能劣化规律

Corrosion characteristics analysis of stainless steel bars based on surface scanning and mechanical properties degradation

为全面了解不锈钢钢筋锈损后的锈蚀分布状态、精确预测其性能退化规律,并厘清不锈钢钢筋与普通钢筋在锈蚀行为上的差异性,本文对混凝土中不锈钢钢筋进行加速锈蚀试验,分别通过3D扫描技术和钢筋拉伸试验得到锈蚀指标和力学性能劣化规律。基于最大截面锈蚀率和锈蚀不均匀系数表征了不锈钢筋的锈蚀程度及锈蚀的不均匀性,得到了不锈钢钢筋坑蚀特征演变规律,研究发现:相较于普通碳素钢,不锈钢钢筋锈蚀更易发生坑蚀,且锈蚀的不均匀程度随着质量锈蚀率的增长而线性增加。不锈钢钢筋断口截面分析表明,蚀坑是导致不锈钢钢筋性能劣化的主要来源。根据拉伸试验探究了不同锈蚀程度下钢筋各项力学指标的退化规律,建立了锈蚀钢筋承载能力退化模型及延伸率退化模型。与普通碳素钢的力学性能对比可以发现,不锈钢钢筋的延性较好,在锈蚀严重的情况下仍能保持一定的延伸率,在防止结构脆性破坏上具有较好的优势。

This study adopts an accelerated corrosion method to achieve corrosion of stainless steel bars embedded in concrete with different target corrosion degrees for an accurate description of steel bar corrosion morphology and a better understanding of corrosion effect.We conduct steel bar tensile tests,use a 3 D scanning technology to examine the corrosion factors and deteriorated mechanical properties of the corroded steel bars,and extract accurate corrosion information from the measurements of 3 D profiles.Corrosion degree and corrosion non-uniformity are represented using the areas loss of the largest cross section and a uniformity parameter.We find that the corrosion of stainless steel is prone to pit corrosion,its unevenness of corrosion is more prominent in comparison to ordinary carbon steel,and the degree of its corrosion non-uniformity increases linearly with corrosion rate.Fracture surface analysis illustrates the necking and fracturing originate from the location of a critical corrosion pit.Through tensile tests,we can examine the degradation of mechanical properties of corroded steel bars with different corrosion degrees,and then develop a model to describe the degradation of their bearing capacity and elongation rate.Comparison to ordinary carbon steel bars reveals stainless steel is much better in ductility and can maintain a certain elongation ratio even in the case of severe corrosion,manifesting a great advantage in preventing structural brittle failure.