| Between 1995 and 2009, the South Dakota Department of Transportation (SDDOT) replaced over 250 miles of two-lane interstate with continuously reinforced concrete pavement (CRCP). After being in service for less than 15 years, several of these pavement sections showed signs of distress, including Y-cracking, network cracking, and cluster cracking. A previous SDDOT study concluded that the impact on performance of these recently constructed CRCP interstates from progressing corrosion of the reinforcing steel due to deicing chemicals is uncertain. Therefore, a separate study was necessary to assess the extent of reinforcement corrosion in South Dakota CRCP interstates, which is the topic of this thesis.;Two main objectives were addressed: determine the character, extent, and severity of corrosion in CRCP constructed in South Dakota since 1995; and identify factors that contribute to observed levels of corrosion. Field work included general observations, crack mapping, dust sampling, core sampling, and half-cell potential measurements of CRCP sections in South Dakota. Laboratory work consisted of chloride ion analysis on core and dust samples, and SEM analyses on the reinforcement in core samples obtained from CRCP in South Dakota. The condition evaluation was performed in two stages: initial evaluation and statewide evaluation.;General observations showed that there were sections of severe and localized reinforcement corrosion at some crack locations. There were also areas in which severe spalling had occurred, but corrosion was not observed. The vertical chloride profiles indicated that chloride concentrations were above the chloride threshold of 1.244 lbs./yd³ in the top one inch of pavement, and decreased to below threshold at the depth of reinforcement in most cases. The horizontal chloride profiles showed that the chloride concentration was above the threshold within the first half inch of a crack in 11 of 13 samples tested. In two of three cases the chloride concentration was above the threshold value within the entire first lateral inch of a vertical crack at the level of the reinforcement. SEM analyses of two out of three cracked core samples and one uncracked sample showed no signs of corrosion. It was also shown that there was a strong correlation between crack density and elevated half-cell potential readings.;The results of this study showed that pavement distresses observed are not necessarily the effect of corroded reinforcement and that reinforcement at cracked locations is susceptible to corrosion caused by deicing salts. The observed significant loss of cross-sectional area in limited sections of reinforcement could cause complete shear failure in these CRCP. Also, crack density is an appropriate means of determining a CRCP section's susceptibility to corrosion. |
