Last year, Utah’s only north-south interstate was modernized using a technique that saved money that was spent on roads and bridges elsewhere in the state: concrete pavement preservation (CPP) with transverse dowel bars.
The 15-mile stretch of Interstate 15 ranged in age from about 20 to more than 35 years old but was in good enough condition to save. Built before transverse dowel bars in new pavements became standard practice, the pavement was faulting, or “thumping,” which produced a rough ride.
The Utah DOT (UDOT) included dowel bar retrofit in the rehabilitation because the aggregate interlock that had originally provided load-transfer capability between slabs was worn away. The bars were needed to reestablish load transfer at the joints.
The dowel bars used were epoxy-coated steel rods measuring 1½x18 inches and precoated with bond-breaking compound. Crews placed the bars in groups of three, one group under each wheel path, and spaced them 12 inches center-to-center. The project used 163,000 bars. Traffic was kept off of the surface until it reached a compressive strength of 3,000 psi.
Specifications unique to UDOT included removing the foam core board to a depth of 2 inches and resealing; Grinding was to begin within 10 working days of placement. Tests were performed on 24 retrofits selected by an agency engineer. Cores were taken to verify that concrete had been properly removed from the slots, the dowels properly placed, and that consolidation had been properly performed.