Na Xu, Xuping Ji and Wanyi Wang
Presented to The 7th International Symposium on Innovation & Sustainability of Modern Railway (ISMR 2020) October 23-25, 2020, Nanchang, China
Keywords: Corrosion, Reinforcing steels, Microcapsules, Electrochemistry, Cementitious materials
The requirements of construction and protection of railways, highways and bridges are increasing with the improvement of the transportation network. In order to effectively delay the corrosion of steel bars in reinforced concrete structures of transportation, the influence of urea-formaldehyde microcapsules on the corrosion performance of reinforcing steel was investigated. Urea formaldehyde polymer microcapsules were synthesized and characterized. The self-healing mortars with different contents of microcapsules were prepared. Both the compressive strengths and the strength repair rates were analyzed to select the appropriate amount of microcapsule for the later corrosion test. After that, two modes (without/with pre-loading) were set to simulate the original and service state of reinforced concrete structure. After undergoing dry-wet alternated accelerated corrosion, the electrochemical tests were implemented to analyze the corrosion performance of the embedded steel. The results show that the epoxy/urea-formaldehyde (UF/E) microcapsules with the size of 150-250 μm had been successfully synthesized. The incorporation of microcapsules slightly reduced the compressive strength of self-healing mortars. Meanwhile the strength repair rate of pre-damaged specimen increased obviously as the content of microcapsules increased. Finally, it is found that the incorporation of the appropriate amount of microcapsules can delay the period of steel bars embedded in self-healing mortars reaching chloride threshold value (CTV). The corrosion protection effect of steel bars embedded in pre-loaded self-healing mortar is particularly obvious. The protective effect of the reinforcing steel was enhanced with the increase of the content of microcapsules.
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