Field Assessment of Cold Recycling Technologies Used for Pavement Preservation

Abstract

Cold recycling of asphalt concrete pavements is a widely practiced technique used to prolong pavement life as a low-cost preservation method. Research in recycled materials has become necessary to further evaluate the material properties and performance of this sustainable technology. The National Center for Asphalt Technology (NCAT) has constructed several test sections as part of its Pavement Preservation Study along Highway US-280 near Opelika, Alabama. The Highway US-280 preservation sections were built in the summer of 2015, and part of the experiment included four different sections using cold recycled techniques surfaced with a one-inch thin overlay. These cold recycled (CR) asphalt pavement included Cold In-place Recycling (CIR) and Cold Central Plant Recycling (CCPR), each one with asphalt emulsion and foamed asphalt as recycling agents. The functional and structural performance of the pavement recycling techniques was evaluated periodically. Rutting and IRI measurements were taken biweekly, deflections were taken quarterly, and crack maps were generated quarterly to assess the influence of CR pavement sections in the thin overlay surface. Field performance measurements showed that the use of cold recycled materials influenced rut depths, falling into the fair threshold of the MAP-21 rating system during the first four and a half years of service. Cracking increase was detected in the last year of this study in the CCPR-emulsion section. Roughness of the section slightly increased over time in most of the sections. FWD backcalculated modulus indicated the cold recycled sections have temperature-dependent behavior, with less temperature susceptibility in the CCPR foamed section. The obtained results were used to evaluate the structural contribution of the recycling technologies from a pavement design perspective. Based on empirical pavement design, it was determined that the recommended structural layer coefficients of the recycled materials ranged between 0.23 and 0.35.