CORROSION RESISTANCE AND SERVICE LIFE OF DRAINAGE CULVERTS

Laboratory/yard tests and a field survey were conducted to determine how chloride-induced corrosion limits the durability of reinforced concrete culvert pipe, and to revise as needed Florida Department of Transportation (FDOT) guidelines for predicting durability. Laboratory tests exposed culvert pipe segments from two different manufacturers to cyclic and continuous saltwater ponding for up to 4.4 years. Yard tests were conducted with full size pipes exposed to saltwater for over 2 years. These tests revealed substantial chloride penetration and corrosion initiation during the exposure period. The results suggest that performance may be improved by the use of higher cementitious content concrete containing fly ash. Culverts exposed in the field to coastal seawater for estimated periods ranging from 27 to 43 years were examined and showed conditions ranging from mild corrosion to severe cracking, although all pipes appeared to be fully functional. Concrete cores of the field samples showed extensive chloride penetration. The results indicate that typical production culverts provide no exceptional protection against chloride penetration or initiation of corrosion, and that evaporative chloride concentration was important. It is proposed that an approach similar to that used by FDOT for estimating service regimes of marine substructure be applied to culvert pipe so that pipes in saltwater having above 2,000 ppm chloride, and having portions immediately above high tide, be treated for service life estimation the same as if exposed to seawater service. It is proposed to retain the present approach (using actual environmental chloride content) for estimating service life for continuing immersion, or environmental water chloride contents of less than 2,000 ppm.