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چکیده
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Coastal concrete bridge deterioration is characterized by a decline in durability, structural safety, and function over time, which can lead to serious safety issues. Particularly, the material deterioration of reinforced concrete reduces its durability owing to the infiltration of environmental substances, such as carbon dioxide and seawater. Carbon dioxide is an aggressive substance that penetrates the pores inside the concrete and reacts with the hydrated calcium compound to modify it. This phenomenon is referred to as concrete carbonation and is an indicator for determining the lifespan of structures. Carbonation activates the penetration of other chlorides and the chemical corrosion of concrete rebars. Chemical corrosion negatively affects the stability of coastal structures, which can cause accidents. Most maintenance methods aim to observe marine bridge deterioration and maintain minimum performance for accident prevention. However, these maintenance methods require a significant budget as the repairs occur after deterioration. Therefore, several researchers have proposed preventative maintenance methods, wherein the deterioration and performance degradation of structures are predicted in advance to ensure effective economic management. Several studies have calculated the carbonation and corrosion of reinforcement structures [1,2]. Typically, corrosion occurs slowly and is analyzed using accelerated testing. These studies aimed to regress the short-term corrosion of concrete within one year. The short-term corrosion model is most affected by the mixing ratio and curing time of the concrete [3]. However, field investigations of the natural environment remain scarce despite numerous experimental and theoretical studies. In general, three limitations are observed in applying the corrosion model to actual bridges. First, the actual coastal bridges over 10 years are significantly affected by environmental variables from a long-term perspective. However, the experimental environment estimates the weights for the environmental parameters because it exposes the concrete only for a short period. The low weighting of environmental variables can deteriorate the performance of long-term corrosion models. Second, most of the design data for bridge structures older than 30 years have been lost. Moreover, the mixing and curing periods of the concrete set in the design stage change owing to errors during the actual construction. These problems prevent the calculation of constants of several developed corrosion models, thereby reducing their usefulness. Third, environmental conditions change because of continuous changes in climate. The increase in the average temperature caused by global warming and the increasing trend of atmospheric CO2 concentration (278 to 400 ppm during the industrial period [4]) may accelerate the corrosion of reinforcement [5,6].
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