Texture, Ride Quality, and the Uniformity of Hot-mix Asphalt Pavements

About the report:

Two years ago, the author completed a study with researchers at Virginia Tech that was designed to develop a tool to measure and control segregation of hot-mix asphalt pavements. This earlier work focused on the application of high-speed texture measurements and ultimately proposed an approach that would discourage segregation by establishing limits on allowable fluctuation of pavement macrotexture. Rather than emphasize segregation detection and measurement, the proposed special provision promoted new-surface uniformity. The activities discussed in this report represent the next step in the process of understanding the relationship between the uniformity and surface characteristics of hot-mix asphalt. The study documents the typical "texture profile" for Virginia's most common surface mixes. It revisits the texture-fluctuation provision proposed in the earlier project and delves into an expanded use of elevation profiles for promoting uniformity. Although the major findings and conclusions from this work do not specifically support a texture-based "segregation specification," the study does advocate continued dedication to material and construction uniformity. Alternatives to a texture-based specification include quality measures that recognize variability of traditional quality characteristics (such as percent defective and percent within limits specifications) and a new approach to reporting and using ride quality data, i.e., "roughness profiles." Whether specifically required or used voluntarily to comply with provisions that have stringent variability components (e.g., ride, texture, density), a properly functioning and operated material transfer vehicle is a proven contributor to good hot-mix uniformity. If the vehicle (at $900/mile) eliminates an estimated $3,000 per lane-mile loss in service life due to low-level segregation, the benefit-to-cost ratio is greater than 3.

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