Zhang Fei, Hu Zhiping, Wei Feng, Wen Xin, Li Xiaoguang, Dai Li, Liu Long
Department of Civil Engineering, School of Civil Engineering, Chang'an University, Xi'an 710064, China.
Department of Safety Engineering, School of Energy Engineering, Yulin University, Yulin 719000, China.
Materials (Basel). 2021 Sep 3;14(17):5054. doi: 10.3390/ma14175054.
The diffusion of sulfate (SO) and chloride (Cl) ions from rivers, salt lakes and saline soil into reinforced concrete is one of the main factors that contributes to the corrosion of steel reinforcing bars, thus reducing their mechanical properties. This work experimentally investigated the corrosion process involving various concentrations of NaCl-NaSO leading to the coupled erosion of concrete. The appearance, weight, and mechanical properties of the concrete were measured throughout the erosion process, and the Cl and SO contents in concrete were determined using Cl rapid testing and spectrophotometry, respectively. Scanning electron microscopy, energy spectrometry, X-ray diffractometry, and mercury porosimetry were also employed to analyze microstructural changes and complex mineral combinations in these samples. The results showed that with higher NaSO concentration and longer exposure time, the mass, compressive strength, and relative dynamic elastic modulus gradually increased and large pores gradually transitioned to medium and small pores. When the NaSO mass fraction in the salt solution was ≥10 wt%, there was a downward trend in the mechanical properties after exposure for a certain period of time. The Cl diffusion rate was thus related to NaSO concentration. When the NaSO mass fraction in solution was ≤5 wt% and exposure time short, SO and cement hydration/corrosion products hindered Cl migration. In a concentrated NaSO environment (≥10 wt%), the Cl diffusion rate was accelerated in the later stages of exposure. These experiments further revealed that the Cl migration rate was higher than that of SO.
硫酸根（SO）和氯离子（Cl）从河流、盐湖和盐渍土向钢筋混凝土中的扩散是导致钢筋腐蚀从而降低其力学性能的主要因素之一。本研究通过实验探究了不同浓度的NaCl-Na₂SO₄导致混凝土耦合侵蚀的腐蚀过程。在整个侵蚀过程中测量了混凝土的外观、重量和力学性能，并分别使用氯离子快速检测法和分光光度法测定了混凝土中的Cl和SO含量。还采用扫描电子显微镜、能谱分析、X射线衍射和压汞法分析了这些样品的微观结构变化和复杂矿物组合。结果表明，随着Na₂SO₄浓度的增加和暴露时间的延长，质量、抗压强度和相对动弹性模量逐渐增大，大孔隙逐渐转变为中、小孔隙。当盐溶液中Na₂SO₄质量分数≥10 wt%时，暴露一定时间后力学性能呈下降趋势。因此，Cl的扩散速率与Na₂SO₄浓度有关。当溶液中Na₂SO₄质量分数≤5 wt%且暴露时间较短时，SO和水泥水化/腐蚀产物会阻碍Cl的迁移。在浓Na₂SO₄环境（≥10 wt%）中，暴露后期Cl的扩散速率加快。这些实验进一步表明，Cl的迁移速率高于SO。
