Effect of Temperature on Cathodic Protection Criteria for Reinforced Concrete Structures


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Title: Effect of Temperature on Cathodic Protection Criteria for Reinforced Concrete Structures

Author(s): Rasheeduzzafar and M. G. Ali

Publication: Special Publication

Volume: 139


Appears on pages(s): 21-40

Keywords: cathodic protection; chlorides; concrete structures; corrosion; reinforced concrete; reinforcing steels; temperature; Materials Research

Date: 9/1/1993

Presents the results of the effect of temperature on cathodic protection level needed for effective control of chloride corrosion of reinforcing steel in concrete structures. The chloride levels in the concrete were 8 and 32 lb/yd 3, and chloride gradients were 1.5 and 2.0. Chloride gradient was created by embedding in the concrete specimen a relatively higher chloride-bearing macrocell and thereafter connecting the macrocell steel and the main steel through an external resistor. Current reversal technique was used to establish the protection level needed for effective control of reinforcing steel corrosion. Two sets of specimens were used: the first set of reference specimens were kept at the controlled room temperature of 25 C, and the second set of temperature-treated specimens were kept in a temperature chamber with a peak value of 60 C. The corrosion activity of the reinforcing steel increased with an increase in the temperature to which concrete is exposed. Increased corrosion activity at a higher temperature exposure of 60 Required an increased level of cathodic protection as indicated by the higher protection current density, higher instant-off protection potential, and marginally higher decay potential at the beginning of the polarization period. The 60 C temperature effect requires about 20 percent higher level of protection in terms of current density and about 20 to 30 mV higher instant-off potential/delay potential for an initial polarization period of two months. Thereafter, no additional protection is required against the temperature effect. The subsequent reduction in the level of cathodic protection required at higher temperature is indicative of a dominant influence of the electromigration factor in the interactive relationship between corrosion activity and the beneficial effect of electromigration of ions caused by higher temperature.