کلیدواژهها
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عنوان مقاله English
نویسندگان English
The surface protection materials have effective results to prevent concretes from corrosion. Reinforced concrete structures have the potential to be very durable and capable of withstanding a variety of adverse environmental conditions. However, failure in the structures does still occur as a result of premature reinforcement corrosion. There are corrosion protection systems and methods to extend the long-term durability of steel reinforced concrete. For example, application of zinc rich or cement based protective primers to reinforcement, surface protection systems of concrete, Cathodic protection using sacrificial zinc anodes, and conductive anode overlays within an impressed current cathodic protection system. In general, the main duty of surface protection is controlling both physical and chemical damages to concrete in order of preventing or reducing from steel bar corrosion and creating a coat of safekeeping against penetration of chloride ion, carbon dioxide, oxygen, and most importantly water. According to European Norm, three types of protection materials are existed based on function mechanism. Coating, hydrophobic impregnation, and impregnation materials are these systems, and two types of them used in this study. In this study, two materials of surface protection have used on the surface of three types of concrete. Two types of self compacting concrete with different w/c ratio and one ordinary concrete with similar mixture design to one of those SCC were used for estimating of durability of concrete. Epoxy resin and silane-siloxane were two types of surface treatment materials used in this study. SEM analysis and water contact angle test were done to study the function mechanism of surface protection material. The other tests are water vapor permeability, corrosion potential, and corrosion intensity. Some of the results of this study is that using this materials have effective impact on declining of corrosion potential, decreasing of corrosion intensity, and after all increasing durability of concrete. As shown in this paper, all of the protected samples except one, until 49th week did not have a sign of corrosion active phase. Increasing in ratio of W/C in the substrate makes weakness in function of this materials. In the other hand, results of half-cell potential of unprotected samples show SCC2 with 0.55 w/c ratio and NC with 0.45 w/c ratio shift from passive to active state in first days and SCC1 with 0.45 w/c ratio attained its active state in 5 weeks. However once corrosion has started in SCC2-EP in 8 weeks, corrosion rate was lower than unprotected samples. In the presence of surface protection systems, due to their ability to reduce water ingress in concrete, the corrosion intensity in all samples were lower than 0.23 µA/ cm^2. The results of water vapor permeability test showed that epoxy can decrease the water vapor permeability up to 65% instead of unprotected concrete. In the meantime, silane-siloxane doesn't have effective results in concrete breathability and have a similar performance to unprotected concrete. The results show using SCC don't have much different effect on quality of the materials function instead of ordinary concrete. Another important result is that protection materials which don't let to enough evaporate, are cause of much corrosion in compare of those that let concrete to breath.
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