Constructed in the early 1970’s, the I-480 viaduct through downtown Omaha, Nebraska consists of 1.5 miles of concrete deck and steel box girders, supported by 66 large conventionally reinforced concrete hammerhead piers. By the mid-1990s the viaduct was showing evidence of significant chloride-induced corrosion and deterioration of the concrete deck and concrete substructure. The corrosion damage on the concrete deck was severe enough to require a complete deck replacement. However, the concrete piers required an evaluation of options to determine the most economical method to meet the 40+ year design service life for the rehabilitated viaduct structure. In order to determine the current status of the concrete piers, a condition evaluation was completed. The evaluation consisted of core testing, petrographic analysis, delamination survey, chloride profile, carbonation testing and a half-cell corrosion potential survey. The evaluation indicated that the existing conditions varied through the structure. With this information in hand, various rehabilitation options could be considered to extend the service life of the concrete piers including: protective coatings, removal and replacement of the chloridecontaminated concrete, impressed current cathodic protection, and electrochemical chloride extraction. Each option had its advantages and disadvantages in cost, service life performance, and disruption to the public. After consideration of these options, it was determined that a combination of strategies would be utilized to rehabilitated the depending upon the conditions. The level of protection could be tailored to suite the varying needs of the structure and achieve the service life objectives.
Thank you to our Premier Sponsors
 |
 |
 |
 |
 |
