Construction and performance of an ultrathin bonded hot-mix asphalt wearing course

In recent years, the need for preserving the investment in the U.S. high-way system has received increased emphasis. An effective pavement preservation program includes several maintenance strategies that are applied in cost-effective and efficient manner. Several new technologies have been developed to address these problems. One of the more promising technologies is the use of an ultrathin bonded hot-mix asphalt (HMA) wearing course (UTBWC). It consists of a layer of HMA laid over a heavy asphalt emulsion layer or membrane. The thickness of the ultrathin surface ranges from 9.5 to 19 mm (3/8 to 3/4 in.). The system is placed on a structurally sound rigid or flexible pavement, which may exhibit minor surface distresses. The process was developed in France in 1986 and has been in use in the United States since 1992. Published experimental project reports and inspections of recently completed projects in many locations indicate good performance of the UTBWC. It provides a surface with excellent macro texture qualities, good aggregate retention, and excellent bonding of the very thin surfacing to the underlying pavement.