Electrochemical chloride extraction on reinforced concrete contaminated external chloride: Efficiencies of intermittent applications and impacts on hydration products

Author(s):  
Thi Hai Yen Nguyen ◽  
Van Mien Tran ◽  
Withit Pansuk ◽  
Nguyen Thi Cao ◽  
Van Hong Linh Bui
Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 398 ◽  
Author(s):  
Chonggen Pan ◽  
Jianghong Mao ◽  
Weiliang Jin

Steel bars embedded in reinforced concrete are vulnerable to corrosion in high chloride environments. Bidirectional electromigration rehabilitation (BIEM) is a novel method to enhance the durability of reinforced concrete by extracting chloride out of concrete and introducing an inhibitor to the surface of the steel bar under the action of an electric field. During the migration process, a higher ionization capacity of the inhibitor with a symmetrical molecular structure was introduced. A new imidazoline inhibitor was, therefore, employed in this study due to its great ionization capacity. The effect of imidazoline and triethylenetetramine inhibitor on chloride migration, corrosion potential, and strength of concrete were explored. The research results showed that the effect of chloride extraction and electrochemical chloride extraction made no significant difference on the surface of the concrete, where chloride extraction efficiency was more than 70%, and the chloride extraction efficiency was more than 90% around the location of the steel. while a dry-wet cycle test, the potential of concrete increased by about 200 mV by mixing imidazoline inhibitor. The imidazoline inhibitor was found to be effective at facilitating chloride migration and ameliorating corrosion, meanwhile, it had a negligible impact on the concrete’s strength.


Author(s):  
Jozef Pritrsky ◽  
Miroslav Brodnan ◽  
Vladimir Necas

The paper deals with the conditional release of low-level radioactive steel from decommissioning in a form of reinforced concrete. The main goal was to determine limits for radionuclides concentration and calculate the annual dose for a member of a critical group of public, which should not exceed 10 μSv/year (according to IAEA Safety Guide RS-G-1.7). Corrosion is the principle mechanism of radionuclides release in this case; therefore effort was devoted to assess the time-dependent rate of steel reinforcement corrosion. It was assumed, that concrete is initially highly alkaline (with pH of 12 to 13) because of hydration products such as calcium hydroxide, which keeps the steel surface passive and protected from corrosion. However, carbonic acid resulting from carbon dioxide and water in the atmosphere can react with these products to produce calcium carbonate. This process is referred to as a “carbonation”, and leads after a period of time to significant reduction of the alkalinity (to pH as low as 8.5) followed by destruction of passive layer and starting corrosion of the embedded steel. The analytical principles and a set of input data have been implemented into a mathematical model developed by means of GoldSim software. The paper presents the results of mathematical simulation of corrosion process, which are compared with real measured values.


2015 ◽  
Vol 754-755 ◽  
pp. 342-347
Author(s):  
Mien Van Tran ◽  
Dong Viet Phuong Tran ◽  
Mohd Mustafa Al Bakri Abdullah

Electrochemical chloride extraction – ECE is an effective method to rehabilitate reinforced concrete structure, which has been corroded. This study investigated concentration of chloride remained in concrete and half-cell potential of the steel reinforcement after ECE using interrupting period of electricity current. Efficiency of ECE using Ca (OH)2was surveyed with two current density of 0.5 and 1A/m2. In this study, ECE treatment was proceeded intermittently in approximately 8 weeks. Results pointed out that chloride concentration decreased to 30 – 60% significantly, especially at in the vicinity of reinforcing steel. Simultaneously, half-cell potential of the steel reinforcement after 4 weeks halted treatment stabilizes in low-corrosion rate.


2011 ◽  
Vol 255-260 ◽  
pp. 699-703
Author(s):  
Yan Xiong ◽  
Di Wu

The damages to reinforced concrete structures subjected high temperature of fire mainly include the followings: high temperature make the microstructure of concrete be loose and porous, the strength of concrete and steel reduce greatly.The alkaline hydration products of cement was decomposed under the high temperature, which would destroy the alkaline environment of concrete around steel and cause the steel corrosion. In this paper, the machanism of realkalization technique is present. Moreover, method of mercury intrusion pore measurement, SEM analysis and investigation on pH Value of concrete pore solutions experiment were carried out to study the durability repairing efficiency of realkalization technique.


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