Corrosion of reinforcing steel and post-tensioned steel in concrete

点击翻译按钮获取中文摘要

Concrete is strong in compression but readily cracks under tensile loads. In reinforced concrete structures, reinforcing bars limit the width of these cracks; however, the presence of cracks makes the bars susceptible to corrosion. Post-tensioning was invented to combat the weakness of concrete under tension. In addition to minimizing cracking in the concrete, post-tensioning reduces the amount of concrete and steel used compared to the conventional reinforced concrete structures, which is economically and environmentally beneficial. All steel embedded in concrete develops a protective film on the surface similar to that which forms on stainless steel and which protects it from corrosion. Nevertheless, the most common cause of failure of reinforced concrete in Canada is corrosion of the reinforcing steel. This is because chlorides from de-icing salts or marine atmospheres penetrate the concrete through pores and cracks in the cement paste and destroy the protective film on the steel. While there is a large body of research on the penetration of chlorides into sound concrete and the resultant corrosion process, much less is known about the role of cracks in exacerbating these processes and how the post-tensioning system fares when exposed to salts.