Remote Measurement of Linear Polarization Resistance In Concrete Structures
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Remote Measurement of Linear Polarization Resistance In Concrete Structures F. Bernal Castillo1, W. Aperador1 and G. Roa-Rodríguez1 1
Universidad Militar Nueva Granada, Bogotá, Colombia.
ABSTRACT The monitoring of corrosion in reinforced concrete structures is considered an important preventive factor against the corrosive damage. The present paper shows the design and construction of a device which performs remote measurements of the polarization resistance of reinforcing steel, this was made using the electrochemical technique of linear polarization resistance as a method to obtain the information of the corrosive process. The development was carried out by implementing a potentiostat based on a free development platform. The design allows to store all the data on a physical memory and to send the results through the mobile network to a web server, where the measured values can be analyzed using an internet connection. The linear polarization resistance measurements were made in cylindrical concrete specimens with rebars of ½ ", each one instrumented with embedded electrodes of Copper/Copper sulfate and graphite. The specimens were subjected to a saturated environment of chlorides (3.5%) where the corrosive process was monitored with the developed system. The results were compared with tests performed on a commercial potentiostat / galvanostat, where the values obtained have an mean of 4.83%.
INTRODUCTION Corrosion in reinforced concrete structures is considered one of the main causes of deterioration in civil constructions [1]. Since the products resulting from the corrosion process are deposited on the surface of steel reinforcement, internal pressures are generated. They produce micro-fractures that increase in size as corrosion continues, and consequently produce cracks that woud cause serious or catastrophic failures in the affected structure [2,3]. Initially, the reinforcements in concrete are protected by a thin oxide layer, produced by high levels of alkalinity from the manufacture of concrete (above 12.5 PH), this protection is affected by the entry of chloride ions which reduce PH level destroying the protective layer and starting the corrosion process [4, 5, 6]. Optimal maintenance of concrete structures requires measurements of the level of corrosion. For that reason, several electrochemical techniques to determine the probability of corrosion and corrosion rate have been developed, allowing to prevent or remedy the damage by taking appropriate actions [7]. One of the most used measurements is the test of probability of corrosion, that follows the standard ASTM C876-91. There are other techniques as electrochemical impedance spectroscopy [8], Tafel polarization curves [9] or linear polarization resistance [10], that show a greater amount of relevant parameters such as corrosion current and corrosion rate.
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