Design and Construction of a Bonded Fiber Concrete Overlay of CRCP (Louisiana, Interstate Route 10, August 1990)

The purpose of this study was the design and construction of a bonded steel fiber reinforced concrete overlay on an existing 8-inch CRC pavement on Interstate 10 south of Baton Rouge, LA. The existing sixteen year old CRC pavement, which is estimated to have carried twice its design load contained several edge punch-out failures per mile. The research objectives were to provide an overlay with a high probability for long term success by using a high strength concrete mix with internal reinforcement and good bonding characteristics. A 4-inch concrete overlay was designed to contain 7.5 sacks of cement and 85 pounds of steel fibers per cubic yard with locally available river garvel as coarse aggregate. An additional ;evel of reinforcement-bonding was provided which utilized curb type reinforcement bars epoxied into the existing slab 8 inches from the outside edge. Water-cement grout was applied to the cleaned surface producing bond strengths in excess of 900 psi. The concrete overlay in combination with 9-inch tied concrete shoulders reduced edge deflections by 60% under a 22,000 pound moving single axle load applied 2 feet from the edge. river gravel as coarse aggregate. An additional level of reinforcement bars epoxied into the existing slab 8-inches from each applied 2-feet from the edge. In general, the Serviceability Index of the pavement increased from 3.4 to 4.4 with measured Profile index levels typically below the 5-inch per mile specification. The bonded overlay has been in service since August 1990 and carries 41,000 ADT interstate traffic. Cores taken over transverse cracks in the original pavement. Anticipation of reflective cracking was one consideration in using the steel fibers which provide three-dimensional reinforcement. Cost figures are provided for surface preparation and for placement of the overlay.