Freeze-thaw environment and steel corrosion should be considered seriously for the durability and structural safety design. Concrete durability rapidly decreases with the increase of freeze-thaw damage, and more pores and cracks are formed, which provide passageways for chloride penetration consequently, the steel corrosion risk significantly increases. In general, concrete cover provides a protection to prevent steel from corrosion, which reduces chloride penetration and provides a related stable environment for steel, but the protection decreases when reinforced concrete is subjected to the freeze-thaw environment. Under chloride environment especially, for example, marine environment, enough chlorides are provided for penetration through the pores and cracks in concrete.
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However, the passivation environment is destroyed with chloride penetrating into concrete, and it leads to the steel corrosion after a series of electrochemical reactions.
The steel is in a state of passivation in reinforced concrete when the interior of concrete is kept in a high alkaline environment (pH 12.5–13.5). Steel corrosion in reinforced concrete produces corrosion products that are approximately two to six times greater in volume than the original steel, which induces expansive pressure on the surrounding concrete and eventually causes cracking of the concrete cover progressing toward the concrete surface. The other main factor is the steel corrosion, and the chloride penetration is considered to be the primary cause of steel corrosion in reinforced concrete. One main factor of durability deterioration is caused by freezing and thawing, and the freeze-thaw damage caused by the expansion stress in concrete is more serious under the coupling environment of freeze-thaw and saturated water.
There are two main factors obviously affecting concrete durability among all. Apart from the structure failure, the significant cause of deterioration is the durability problem. As demand for concrete structures in harsh environment increases, the concern toward long service lives of reinforced concrete structures also increases. Under harsh environment especially, concrete durability rapidly decreases. However, attributing to the unique composite materials that are porous and highly heterogeneous, the passageways are provided for the water and chloride penetrations into concrete, which reduce the concrete durability. IntroductionĬoncrete is a heterogeneous material with a high strength, and it also possesses a good versatility and relatively low cost, which makes concrete a man-made building material all over the world. The steel corrosion and bond-slip behavior of reinforced concrete should be considered serious under freeze-thaw cycles environment, which significantly impact the durability and safety of concrete structure. Moreover, there exists a good correlation between the parameters of bond-slip and freeze-thaw cycles. The bond-slip behavior of reinforced concrete with corroded steel decreases with the increase of freeze-thaw damage, especially for the concrete that suffered high freeze-thaw cycles. Moreover, increasing the thicknesses of concrete cover is also an effective method of improving the resistance to steel corrosion. Compared with the ordinary concrete, both air entrained concrete and waterproofing concrete possess better resistance to steel corrosion under the same freeze-thaw environment. The results show that the freeze-thaw damage aggravates the steel corrosion in concrete, and the results become more obvious in the concrete after suffering serious freeze-thaw damage. Additionally, the bond-slip behavior of the reinforced concrete after suffering the freeze-thaw damage and steel corrosion has also be presented. The influence of thickness of concrete cover is also discussed. This paper mainly studies the behavior of steel corrosion in various reinforced concrete under freeze-thaw environment.