Characteristic and random law of roughness factor on corroded surface = Đặc trưng và quy luật ngẫu nhiên của hệ số độ nhám bề mặt bị ăn mòn

Abstract

The corrosion propagation process, the formation of local corrosion, and the surface roughness characteristics of corroded steel structures when working with concrete are presented in detail in this study. The 36 steel specimens working with concrete wereconducted to determine the corrosion propagation process, and then the accelerated cyclic corrosion tests were also performed on these 36 specimens. When exposed to a corrosive environment, the boundary between the steel structure and concrete will immediately corroded, creating a local corrosion zone here. Then the corrosion begins to spread gradually at an increasing rate, the gap between the concrete and the steel structure develops rapidly. In the early stages of corrosion, the surface tends to corrode uniformly, the corrosion is evenly distributed over the entire surface, the arithmetic average of the absolute values Ra increases gradually over time and tends to be predictable when the corrosion is still uniform. However, when the corrosion increases, the Ra value does not follow the trend and is formed randomly. In the first exposure period, the distribution of corrosion depth trends to follow the exponential or lognormal function, while it follows normal function for an older exposure period. This is a characteristic when the corroded surface appears with localized corrosion. The value of roughness factor Ra = 0.034 mm was proposed as the threshold value that the corroded surface will be transferred from the uniform corrosion to local corrosion. The knowledge gained from this study will supplement the analysis of the corrosion propagation process, and also supplement data in the design, warranty, and maintenance of steel structures subject to corrosion when working with concrete.