Asphalt surface treatments are among the most efficient and cost-effective methods utilized by state highway agencies to preserve and rejuvenate existing pavements. Specific benefits of using surface treatments include sealing pavements against water and air, restoring weathered and raveled surfaces, and providing skid-resistant surfaces, to name a few. However, the economic advantages of surface treatments may easily be forfeited through faulty design or poor mixture characteristics. Although many design methods exist, most state agencies still rely on experience and/or precedent in designing their mixtures, a practice that often results in surface treatments with poor performance.
Due to the ongoing commitment to pavement preservation and the growing number of miles of low volume roads, the use of surface treatments has increased substantially in recent years and is likely to continue to rise in the future. This increase in the use of surface treatments has led state agencies to invest in reviewing their design procedures and to modify their existing specifications and develop new mix design systems. Such systems would address material selection, mixture characteristics, performance evaluation, and other influencing factors such as traffic, climate, and existing pavement conditions.
The primary objectives of the proposed research are:to obtain material properties, particularly aggregate gradation, and mix design guidelines for typical surface treatments in North Carolina as well as other states;to determine particular mix characteristics and performance criteria related to aggregate retention, bleeding, and skid resistance;to study the effects of aggregate gradation and other mix characteristics on performance and evaluate life cycle costs; andto propose guidelines for the design of new mixtures and/or modifications of existing specifications.
The developed guidelines and recommended modifications to the existing specifications will provide the NCDOT with a tool to improve performance of surface treatments. This provision may be in the form of improved operational efficiency, longer service life, and improved ride quality, which together would lower life cycle costs and increase safety and customer satisfaction.
