Some sections of continuously reinforced concrete pavement (CRCPI in Minnesota are experiencing a spalling-type deterioration caused by corrosion of the reinforcing steel. In an attempt to develop a method of stopping this corrosion, a cathodic protection system was designed and installed along a 1000-ft section of Interstate CRCP just north of St. Paul. High silicone chromium iron alloy anodes energized by a constant-current output rectifier were placed at the edge of the 10-ft bituminous shoulder at 50-ft intervals. On half the project, the anodes were buried in a trench that was backfilled with coke breeze. On the other half of the project, canisters containing the anodes packed in coke breeze were placed in post holes and backfilled with additional coke breeze. It appears that both types of installation are providing at least partial cathodic protection to the pavement.

During the late 1960s, the Minnesota Department of Transportation(MnDOT) constructed considerable mileage of continuously reinforced concrete pavement (CRCP). In rural areas pavement thickness was generally 8 in and in urban areas 9 in. The steel reinforcement was 0. 6-0. 7 percent and was deformed wire mesh or deformed reinforcing bar. During the past seven years, an increasing number of CRCP sections in Minnesota have begun to show a spalling-type deterioration. The frequency of this deterioration progressed from isolated and random in 1975 to widespread and concentrated on certain pavement designs by 1978. Pavements showing the most severe spalling are of the two-course construction type with a steel-to-concrete ratio of 0.60-0.65 percent. Reinforcement used was deformed wire mesh with specified clear cover of 2-4 in. In most cases the steel had been placed at the minimum specified cover of 2 in.