EAGER: Corrosion Reduction in Reinforcing Steel of Concrete Structures through Grain Size Alteration

混凝土结构中钢筋的腐蚀是混凝土结构劣化的关键参数之一。假设减小钢的晶粒尺寸可以显著减少钢筋的腐蚀。将进行分析和实验研究，以确定晶粒尺寸和腐蚀程度之间的关系。这个早期概念探索性研究资助项目的实验将包括把钢筋放在模拟的混凝土环境中。用热循环来改变钢的晶粒尺寸，以确定晶粒尺寸对腐蚀和机械性能的影响。钢筋将受到氯化物污染的混凝土孔隙溶液，腐蚀钢筋的腐蚀程度将通过不同的微观和光谱分析来评估。通过标准试验可以得到不同晶粒尺寸的钢的力学性能。在这个探索性项目中，将进行改变晶粒尺寸的成本分析，以确定该工艺的可行性。利用电子背散射衍射技术获得定量的显微组织图，对钢试样的晶体性质进行分析。该技术揭示了样品的晶粒尺寸、晶界特征、晶粒取向、织构和相特性。分析模型中的显微组织图将允许预测不同晶粒尺寸钢的点蚀行为。使用扫描电化学显微镜、x射线光电子能谱和光学剖面仪可以获得钢的物理和化学成分。分析模型将把点蚀增长作为一个变量。生命周期成本分析将根据减少腐蚀所需的晶粒尺寸进行。为此目的，将使用成本分析标准中的一个程序来衡量建筑物的生命周期成本。这个探索性项目的最终结果将是了解腐蚀与暴露在混凝土环境中的钢的晶粒尺寸有关。

Corrosion of reinforcing steel in concrete structures is one of the critical parameters in deterioration of concrete structures. It is hypothesized that reduction in grain size in steel can significantly reduce corrosion in reinforcing bars. Analytical and experimental studies will be pursued to correlate between grain size and level of corrosion. The experiments in this EArly-concept Grant for Exploratory Research (EAGER) project will include putting the reinforcing steel in the simulated concrete environment. The grain size in steel will be altered using thermal cycles to determine effects of grain size on corrosion and mechanical properties. The reinforcing steel will be subjected to chloride contaminated concrete pore solution and the level of corrosion on the corroded steel bars will be assessed using different microscopic and spectroscopic analyses. Mechanical properties of the steel with different grain sizes will be obtained with standard tests. Cost analysis of the alteration of grain size will be pursued in this exploratory project to determine viability of the process.Electron backscatter diffraction technique to obtain quantitative microstructural map will be used for crystallographic nature of the steel specimens. This technique reveals grain size, grain boundary character, grain orientation, texture, and phase identity of the specimens. The microstructural map in an analytical model will allow predicting the pitting corrosion behavior of steel with different grain sizes. Physical and chemical composition of the steel will be obtained using scanning electrochemical microscopy, X-ray photoelectron spectroscopy, and optical profiler. The analytical model will include pitting growth as a variable. Life cycle cost analysis will be pursued as related to grain size necessary to reduce corrosion. A procedure that is in a standard for cost analysis for measuring life cycle costs in buildings will be used for this purpose. The final results of this exploratory project will be to understand corrosion as related to grain size of steel exposed to environment of concrete.