During the spring of 2013, the Utah Department of Transportation (UDOT) began rehabilitating a 15-mile stretch of freeway. Not only is Interstate 15 the only north-south interstate highway in Utah, it’s also the state’s only major north-south road for high-speed travel and is a major truck route. Even after decades of use, the pavement was still in good enough condition to save, so UDOT elected to perform concrete pavement preservation (CPP).

The pavement ranged in age from about 20 to 35+ years old, and was constructed before the use of transverse dowel bars in new pavements became standard practice. It had experienced some faulting or “thumping,” which produced a rough ride. CPP methods used for the project included some partial and full-panel patching where panels were cracked or spalled; slabjacking; resealing; dowel bar retrofit; and diamond grinding.

The rehabilitation included dowel bar retrofit because the aggregate interlock that had originally provided load-transfer capability between slabs was worn away and dowel bars were needed to re-establish load transfer at the joints. The dowel bars used were epoxy-coated steel rods measuring 1½x18 inches and pre-coated 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 I-15 project used 163,000 bars.

Specifications unique to UDOT included removing the foam core board to a depth of 2 inches and resealing. UDOT also required that grinding start within 10 working days of placing the retrofits. Tests were performed on 24 retrofits, as selected by the engineer, and cores were taken to verify that concrete had been properly removed from the slots, dowels had been properly placed, and consolidation had been properly performed. Traffic was kept off of the surface until it reached a compressive strength of 3,000 psi.

“Looking outside the box allowed UDOT to provide a safe, smooth ride while saving considerable sums of money that could be used to improve their transportation infrastructure elsewhere in the state,” says John Roberts, executive director of the International Grooving & Grinding Association.