DESIGN AND CONSTRUCTION OF BONDED FIBER CONCRETE OVERLAY OF CONTINUOUSLY REINFORCED CONCRETE PAVEMENT

The purpose of this research was to study the design and construction of a bonded, steel-fiber-reinforced concrete overlay on an existing 8-in. continuously reinforced concrete pavement (CRCP) on Interstate 10 south of Baton Rouge, Louisiana. The existing 16-year-old CRCP, 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-in. concrete overlay containing steel fibers was designed. An inverted U-shaped reinforcing bar was added at the edge of the pavement to provide positive edge bonding. Shot blast surface cleaning of the existing tine surface easily met a specification requiring an average texture depth of 0.045 in. Water-cement grout was applied to the cleaned surface, producing bond strengths in excess of 900 psi. The concrete overlay in combination with 9-in. tied concrete shoulders reduced edge deflections by 60% under a 22,000-lb moving single axle load applied 2 ft 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-in./mi specification. The bonded overlay has been in service since August 1990 and carries average daily traffic of 41,000 vehicles. Cores taken over transverse cracks in the overlay indicated reflection cracking from transverse cracks in the original pavement. Anticipation of reflective cracking was one consideration in using the steel fibers, which provide three-dimensional reinforcement.