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原文传递 Corrosion Propagation of Carbon Steel Rebars in High Performance Concrete.

题名：	Corrosion Propagation of Carbon Steel Rebars in High Performance Concrete.
作者：	Presuel-Moreno, F. J.; Bencosme, R.; Hoque, K.; Nazim, M.; Kazemi, A.; Tang, F.
关键词：	Reinforced concrete, Corrosion initiation, Electromigration, High performance concrete, Corrosion propagation, Forensic examination, Pitting factor, Exposure time
摘要：	A better understanding of the corrosion propagation of carbon steel rebar embedded in high performance concrete is needed. The project aim was to fill some of the knowledge gaps. The study used samples exposed outdoors (now) for over 24 years to wet/dry cycles with seawater. The concrete of these samples can be considered high performance concrete because in some of the mixes prepared, the fly ash content ranged from 20 percent to 50 percent, and in other mixes, the amount of silica fume was varied. The corrosion rate was monitored over 18 months using a commercial rebar potential and rebar corrosion rate monitoring device. Accelerated chloride transport was applied via electromigration to samples exposed indoors. Electromigration worked well to accelerate the initiation of corrosion. The indoor samples had concrete covers that ranged from 5 cm to 0.8 cm. The length of the solution reservoir ranged from 2.5 cm to 17 cm. Four types of samples were prepared in 2016, and samples prepared as apart of previous research efforts were also used. The concrete composition in some of the samples were 50 percent blast furnace slag; in others, 20 percent fly ash. A smaller number of samples were prepared with 20 percent fly ash and 8 percent silica fume, a similar number of samples were prepared with 50 percent blast furnace slag and 20 percent fly ash. The rebar potentials, polarization resistance, and solution resistance were monitored after installing the solution reservoirs. More than a year's worth of data was used to assess the corrosion propagation stage. Selected samples were identified for forensic analysis from both indoor and outdoor samples. The concrete surface was assessed, and in some cases, cracks were present. The rebars were cleaned, and the mass fraction loss determined (for those with significant mass loss) and compared to the measured corrosion rate. It was found that cracks occurred on some of the specimens cast with high performance concrete and that the duration of the corrosion propagation that caused the cracks was a few years. (If the corrosion initiation is considered from a large potential drop, the duration would be longer if the corrosion propagation is counted from when a more gradual rebar potential drop started). Corrosion appears to have initiated at small sites and did not appear to have grown significantly on samples subjected to accelerated chloride transport as part of this project.
报告类型：	科技报告