CONSTRUCTION OF THIN BONDED CONCRETE OVERLAY

In 1981 a bonded concrete overlay 3 in. thick was placed on I-81 north of Syracuse under a contract with the New York State Department of Transportation. I-81 is a six-lane divided Interstate highway that has an annual average daily traffic of 23,000 with 8 percent trucks. The existing concrete pavement was overlaid for a length of 3 miles in all northbound and southbound lanes. Two lanes in each direction were closed to traffic while the overlay was placed. Traffic was maintained on the third lane and a thickened asphalt-concrete shoulder. The concrete overlay was placed to remedy widespread longitudinal and transverse joint deterioration caused by porous coarse aggregate in the existing concrete pavement. The freezing and thawing of water in the coarse aggregate caused a surface spalling problem and layered cracking beneath the surface similar to D-cracking. Deteriorated pavement at the joints was removed to a 3-in. depth by using a milling machine. A nominal 3-in-thick concrete overlay was bonded to the existing pavement with a cement-sand grout after scarification, sandblasting, and cleaning. The resulting 6-in.-thick lift of concrete at the deteriorated joints was designed to bridge the deterioration and provide a long-lasting overlay. Pavement blowups were occurring on the 23-yr-old existing pavement, which dictated the installation of pressure relief joints before overlaying. The surface preparation and cement-sand grout have resulted in an adequate bond. The thicker concrete overlay is briding the deterioration. Shrinkage cracking, which devloped during paving in hot weather, and reflection cracks over existing pavement cracks have not resulted in performance problems to date. Dust control during surface preparation needs improvement. Pavement friction generally is adequate but needs further study. Overall rideability is excellent. (Author)