Corrosion in reinforced concrete bridge decks has always been a concern amongst engineers. However, as structures continue to increase in size and in the amount of reinforcement present, consideration must be given to parameters such as the clear spacing arrangements between bars, the presence and absence of stay-in-place (SIP) forms, and differences in the cathode bar to anode bar ratios. Limited research has been performed to determine the effects of the parameters (Shiessel, P. 1986). Research has been conducted on the effects of macrocell corrosion compared to microcell corrosion. Previous studies have shown that the measured microcell corrosion is not augmented greatly by the macrocell current (Andrade et al. 1991). In this study, twenty-seven specimens were cast with reinforcing steel to represent reinforcing mats at the top and bottom of each specimen. Top and bottom spacing arrangements were approximately 51, 76, 102 mm (2, 3, and 4-inches), cathode-to-anode bar (C/A) ratios were 2 and 1, and the presence and absence of SIP were considered. Macrocell currents, resistivity measurements, half-cell potential measurements, and corrosion current densities were recorded over a 273 day time period to compare the differences that existed amongst the three different parameters. Based upon the data that was collected, no significant differences were recorded when comparisons were made between the spacing arrangements, the absence and presence of SIP, and differences in C/A ratios. The formation of the passive layer was confirmed by the corrosion current densities and half-cell potentials. The rate of the formation of the passive layer occurred in two distinct periods, a rapid rate from casting to about 105 days and a significantly slower rate beyond 105 days after casting. There was no detected influence of the macrocell activity on the formation of the passive layer throughout the 273 day study period. / Master of Science

Chloride induced corrosion of steel in concrete is one of the major forms of deterioration mechanisms found in reinforced concrete bridges. Early age corrosion damage reduces the lifespan of the bridges, which results in heavy economic losses. Research has been conducted to identify economic solutions for significantly delaying and/or preventing corrosion damage. Considering the amount of steel reinforcement used in bridge decks, the influence of as constructed parameters including clear spacing between top and bottom reinforcement bars, ratio of cathode to anode areas, and presence of stay-in-place forms on corrosion activity needs to be evaluated. The influence of the as constructed parameters have been studied using different corrosion assessment methods including resistivity, half-cell potential, linear polarization, chloride content, moisture content, and visual inspection. This study included the clear spacing distances between the anode and cathode of 51, 76, and 102 mm (2, 3, and 4-inch), number of cathodes as 1 and 2, and the presence and absence of stay-in-place forms. Data up to 15 months were taken from a previous study by Smolinski and integrated into the current study period of 35 to 45 months. A trend line may be established to illustrate the changes which took place over the missing time period, from approximately 15 to 35 months, since the specimens were maintained in controlled environment. Analysis of the data showed that there is a significant difference between the spacing values (2, 3, and 4-inch) through all forms of evaluations. Regarding the other parameters, no significant difference was identified. Variations in resistivity with increasing spacing, even when the water-cement ratio was kept at 0.50, maybe the result of the difference in unit consolidation between the clear spacing specimens. Thus, the corrosion mechanism observed in this study may be resistivity-controlled. Also, autopsy showed that corrosion on the top bars was in general agreement with the measured corrosion activity. The bottom bars had no visible corrosion and the chloride had not penetrated to the bottom bars, regardless of the separation distance between the top and bottom bars. For this laboratory study, the measurements showed that macrocell corrosion influence on the total corrosion was insignificant. / Master of Science