Crown Center Parking Garage - Cathodic Protection of Reinforced Concrete Structures

The Crown Center Garage is a multi-level parking facility in Kansas City, Missouri that was built in 1970. The structural design consists of a 9-in. (230 mm) thick two way flat slab system with conventional reinforcing bars. The total surface area of the five elevated parking levels is approximately 530,000 ft2 (50,000 m2).

By 1980, salt had penetrated to the top level of rebar and the concrete slab was suffering from chloride-induced corrosion. A major repair program was initiated in 1981 to rehabilitate the structure. Delaminated concrete was removed and exposed reinforcing bars were sand-blasted. The slabs were then patched and overlaid monolithically with 1.5 inches (38 mm) of latex modified concrete.

Three years after the repair, the slab was again showing distress from reinforcing steel corrosion. A significant amount of corrosion activity was threatening to destroy the previous repair. Cracks in the latex topping were allowing moisture to penetrate to the reinforcing steel surface. If left unchecked, the corrosion would result in serious structural damage. Replacement of the slab was considered a possibility.

Cathodic protection (CP) was recommended by Kansas City consultant Structural Engineering Associates (SEA) as a possible solution to control the corrosion problem and prolong the life of the structure. Several trial CP systems were installed at Crown Center. The purpose of the trials was to determine which system was the most effective in controlling rebar corrosion and to provide a budget estimate for the installation of a permanent system.

Of the systems tested, the ELGARD™ titanium anode ribbon in slots proved to be the most cost effective system and had the best overall performance. Since 1989, over 345,000 ft2 (32,000 m2) of ELGARD™ CP has been installed at Crown Center. Subsequent field surveys conducted by SEA have indicated a high level of corrosion protection to the reinforcing steel and the elimination of delamination growth.

Project Data
Structure:  Crown Center Parking Garage
Location:  Kansas City, MO

Installation Date / Size
1987 - Trial (1,600 sq. ft.)
1989 - Gold Level (184,000 sq. ft.)
1990 - Orange Level ( 60,000 sq. ft.)
1994 - Blue Level (99,700 sq. ft.)

Leading governmental and independent trade organizations have monitored, tested and reported on corrosion control strategies over the past three decades. These groups include the American Concrete Institute, National Association of Corrosion Engineers and Federal Highway Administration. They advocate CP as the only rehabilitation technique that effectively stops corrosion in salt-contaminated structures, regardless of the chloride content of the concrete.

ELGARD™ is a trademark of Eltech Systems Corporation.