Comparison of Thin-Lift Hot-Mix Asphalt Surface Course Mixes in New Jersey

Abstract

The use of thin-lift hot-mix asphalt (HMA) surface course mixes has gained wide acceptance in the United States as a means of improving ride quality and safety. Generally, these materials are classified as having an open-graded and gap-graded aggregate skeleton, nominal aggregate sizes of 12.5 mm or less, and higher than normal asphalt binder contents and are placed in thicknesses of less than 1 in. (25 mm). The use of the thin-lift materials has been found to improve wet-weather driving conditions, reduce traffic noise associated with the tire–pavement interface, and improve ride quality measurements. Typically, thin-lift HMA surface course mixes found in New Jersey consist of open-graded friction courses and Novachip, with a few roadway sections using microsurfacing and stone-mastic asphalt. Each of these material types is evaluated to provide an assessment of their ride quality and safety. These thin-lift materials are compared with in-service dense-graded asphalt mixes and portland cement concrete (PCC). PCC pavements have three different surface conditions: no treatment, transverse tined, and diamond grind. To establish performance comparisons between the different surface courses, noise measurements using the close proximity method, wet-skid resistance, and ride quality data consisting of the ride quality index and international roughness index were used. The performance information, along with current costs associated with the materials and construction, can provide a means of establishing the cost-effectiveness for the use of these surface treatments under specific situational conditions.