Award of Excellence: Historic Category
Repair of Cabrillo Bridge in Balboa Park
San Diego, California
Submitted by BASF Building Systems
State of California Department of Transportation
Bel Air, California
Deer Park, Texas
BASF Building Systems
The Cabrillo Bridge, entered on the National Register of Historic Places in 1976, is one of the most historic bridges in all of California. The bridge, which passes over California Highway 163 in San Diego’s Balboa Park, has the architectural appearance of seven closed-spandrel cast-in-place reinforced concrete arches, and mimics the Spanish-Colonial style. Structurally, however, it is composed of hollow vertical sections with cantilevered box girders that form the arched openings. The concrete walls are 6 to 24 in. (15 to 61 cm) thick and made with board formed concrete. The original formwork from 1915 is still in place inside the columns.
Chunks of original concrete from beneath the arches had become dislodged and fallen to the ground below. Concerns about safety and potential structural performance problems prompted an investigation to be done in connection with bridge repairs being performed by the contractor and Department of Transportation.
Inspection and test results showed the primary cause of concrete spalling and delamination to be corrosion of embedded steel reinforcement. Factors contributing to steel corrosion over the bridge’s service life included concrete carbonation, available moisture sources, and depth of concrete cover over reinforcing steel; general concrete quality; and chloride levels.
The consulting structural engineer’s report described how the concrete’s durability potential could be enhanced through further repairs, such as shotcrete or form-and-pour patches, or alternative repairs involving sacrificial anodes, penetrating corrosion inhibitors, impressed current cathodic protection, or concrete realkalization, included in an ongoing repair and maintenance program.