Comparison of Thin-Lift Hot-Mix Asphalt Surface Course Mixes in New Jersey (05-1766)**
Thomas A. Bennert, Rutgers University
Frank Fee, Asphalt Pavement Technology, LLC
Eileen C. Sheehy, New Jersey Department of Transportation
Andris A. Jumikis, New Jersey Department of Transportation
Robert W. Sauber, Consultant

The use of thin-lift HMA surface course mixes is starting gaining wide acceptance in the United States as a means of improving both ride quality and safety. These materials are generally classified as having an open-graded/gap-graded aggregate skeleton, nominal aggregate sizes of 12.5mm or less, higher than normal asphalt binder contents, and are placed in thickness’ less than one inch. The use of the thin-lift materials has found to improve wet weather driving conditions, reduce traffic noise associated with the tire/pavement interface, and improve the ride quality measurements. Thin-lift HMA surface course mixes typically found in New Jersey consist of open-graded friction courses (OGFC) and Novachip®, with a few roadway sections using micro-surfacing and stone-mastic asphalt (SMA). Each of these material types were evaluated to provide an assessment of their ride quality and safety. These thin-lift materials were compared to in-service dense-graded asphalt mixes (DGA) and Portland cement concrete (PCC). The PCC had surfaces that consisted on no treatment, transverse tined, and diamond grind. Noise measurements utilizing the Close Proximity method (CPX), wet skid resistance, and ride quality data consisting of RQI and IRI were used to establish “performance” comparisons between the different surface courses. The “performance” information, along with current costs associated with the materials and construction, can provide a means of establishing a cost-effectiveness for utilizing these surface treatments under specific situational conditions.