Ultrathin Bonded Wearing Course as Pavement Preservation Treatment for Jointed Concrete Pavements

Use of an ultrathin bonded wearing course (UTBWC) is reported on as a pavement preservation strategy for jointed plain concrete pavements. This strategy has been used in North Carolina on both urban and rural sections. One of the benefits of the UTBWC is that the elevation change is small, typically 5/8 in. Expenses associated with thick overlays—such as adjustments to signs, guardrails, bridge clearances, and shoulders—are minimized. The effectiveness of the UTBWC in improving ride quality and extending pavement life is evaluated for five projects. North Carolina performs pavement condition surveys every year on the Interstate system and every other year on other systems. On jointed concrete pavements, a sample of 39 to 41 slabs is used for the first 0.1 mi of each mile. Asphalt-surfaced roadways are evaluated by using 100% coverage in a windshield survey. Application of the ultrathin bonded overlays resulted in a dramatic bump in the pavement condition ratings (PCRs). The rate of decline of the PCR after resurfacing with UTBWC is between 0.8 and 3.0 points per year on the basis of two sites. Most decline in PCR to date is associated with reflection cracking, which appears but does not degrade rapidly. Faulting ultimately results in decreased ride quality over time as indicated by increases in international roughness index (IRI). The rate of increase in IRI ranged from 0.5 to 2.1 points per year. On the basis of North Carolina's experience with UTBWC on poor-quality jointed portland cement concrete, a life of 6 to 10 years is attainable and is supported by the projections of performance curves from two of the sites.