Applicability Study On Electrifying Corrosion Methods Of Reinforced Concrete Members

The primary reason for the loss of durability of concrete structures is steel corrosion.Currently, the researches on the steel corrosion use the electrifying accelerated corrosionmethod which is simple, short cycle, low-cost and so on. But many scholars have differentviews about controlling factors and corrosion effects of this method. Therefore, it isnecessary to study this method systematically and propose the control targets whosecorrosion effects are most similar to natural corrosion.In the two-stage of concrete protective layer crack, the electrifying acceleratedcorrosion method have been researched by controlling three variables who are differentsteel types, different current densities, different power modes. And the accuracy offaraday’s law of electrolysis has been comparative analyzed by the same material of rebar.During the test, the waterproof strain gages on the surface of concrete which have a goodwaterproof effect have been invented. At the same time, the author has designed amultifunctional concrete specimens splitting tensile equipment which made the testsmoothly.The results show that under the same energized conditions, the measured corrosionrate of the reinforced concrete after electrifying accelerated corrosion is lower than theoreticalcorrosion rate. However, the measured corrosion rate of bars is higher than theoreticalcorrosion rate. But the measured corrosion rate has a good correlation with theoreticalcorrosion rate calculated by Faraday’s law of electrolysis. The measured corrosion rate underdifferent conditions can be worked out by the appropriate factor multiplied by theoreticalcorrosion rate.Under the same chlorine concentration and current density, corrosion efficiency ofplain bars after electrifying accelerated corrosion is higher than deformed bars. And theessential reason that they have different corrosion efficiency is the different surface shapeof two kinds of bars. Under the same chlorine concentration and steel types, the bars’corrosion efficiency under high current density is higher than the bars’ corrosion efficiencyunder low current density. Under the same steel types and current density, differentchlorine concentration have nothing impact on the bars’ corrosion efficiency.In the two-stage of concrete protective layer crack after electrifying acceleratedcorrosion, the bars which corroded by full immersion power mode have highest corrosionefficiency, followed by half immersion power mode, electro-migration power mode lowest. Under the same energized conditions, the plain bars’ corrosion efficiency is higher thandeformed bars’ corrosion efficiency. This conclusion is the same with the previousconclusion obtained by bars’ test electrifying corrosion.The bars’ corrosion morphology and corrosion products produced during the test areanalyzed. The results show that the corrosion part of reinforced concrete is related with theposition of negative electrode and current trend. Therefore, reinforced concrete’s corrosioneffect can be controlled during the process of electricity. The reinforced concrete’scorrosion products contain more Fe3O4before the concrete protective layer cracking.However, the reinforced concrete’s corrosion products contain more Fe2O3and FeO(OH)after the concrete protective layer cracking. The corrosion products when corroded by fullimmersion power mode contain more Fe2O3. More Fe3O4are contained by the corrosionproducts when corroded by half immersion. And the main components when corroded byelectro-migration power mode are Fe(OH)2and FeO(OH). The morphology of corrosionproducts under three kinds of power modes is different. The energized corrosion products’compactness is lower than the natural corrosion products’. And the natural corrosionproducts are the compounds of Fe and O. But the energized corrosion products are themixtures of rust and cement gel. According to the relevant formula, the expression ofcorrosion products’ volume expansion ratio has been get. And it is only related to thedensity, volume expansion ratio and mass percentage of components. The volumeexpansion ratio of reinforced concrete’s corrosion products under different conditions iscloser, between2.05to2.63.