Character, Extent, and Severity of Corrosion in Continuously Reinforced Pavements in South Dakota
A major drawback of continuously reinforced concrete pavement (CRCP) is the potential for the steel reinforcement to corrode. The corrosion process is initiated and accelerated when deicing chemicals, used extensively during winter maintenance, penetrate through the cracks and reach the steel reinforcement. The expansion of the corroded reinforcement leads to spalling of concrete and rapid degradation of the pavement section.
CRCPs constructed in South Dakota as part of the original Interstate Highway System (pre-1995) have performed well with little to no observed corrosion of steel reinforcement. However, recent surveys conducted by the South Dakota Department of Transportation (SDDOT) indicate a strong likelihood of potential future problems in newer CRCPs (post-1995) with corrosion of the reinforcing steel. SDDOT is interested in determining cost-effective maintenance and rehabilitation strategies to maintain and extend the life of inservice CRCPs exhibiting unexpected levels of cracking and distress for the post-1995 CRCPs.
An extensive field and laboratory testing program was initiated to define the character, extent, and severity of corrosion in CRCPs constructed in South Dakota since 1995 and to identify factors and interactions among factors that contribute to observed levels of corrosion. Field evaluations included detailed crack mapping, half-cell potential measurements, dust sample profiling, and core sampling. Dust samples were tested for chloride content, and the core samples were examined under a scanning electron microscope for imaging, X-ray spectrum, semi-quantitative analysis of the X-ray spectrum, and elemental mapping. The results of the field and laboratory testing were used to evaluate the reinforcement condition of eight representative sites across South Dakota.
The results of this study show that the distress in CRCP is not necessarily the result of reinforcement corrosion. Corrosion of the reinforcement occurred only at locations of cracks in the CRCP where chlorides could penetrate and reach the reinforcement. In intact (uncracked) concrete, the chloride content from deicing salts was insignificant and was below the threshold for corrosion at the level of the reinforcement. The half-cell potential Numeric Magnitude Technique was not a good indicator of the probability of corrosion in CRCP. However, in general, a strong correlation was observed between the crack density in the pavement and elevated half-cell potential readings.
Presented at FHWA’s International Conference on Long-Life Concrete Pavements in 2012.
Authors: Allen L. Jones, Nadim Wehbe, and Stephanie Klay