Oregon DOT SPR 777
Federal Highway Administration State Planning and Research Funding
Oregon Department of Transportation
Chris Williamsrwilliam@iastate.edu email >
About the research
Chip seals or seal coats, are a pavement preservation method constructed using a layer of asphalt binder that is covered by a uniformly graded aggregate. The benefits of chip seal include: sealing surface cracks, keeping water from penetrating the surface, provides an anti-glare surface, minimizes the effect of aging as it seals the pavement surface, provides a highly skid-resistant surface, and is cost effective.
This study summarizes performance and the methodology used for developing specifications and a rational chip seal design in Oregon. Test sections included both emulsified asphalt and hot-applied chip seal applications. The pre- and post-construction pavement performance information is presented and analyzed. Post-construction analysis of the chip seals includes macrotexture analysis, dynamic friction testing to measure microtexture, and pavement performance surveys. The underlying pavement conditions were classified from being very good to very poor performance. In this study, a comparison of field performance on test section is developed to recommend best practices and develop a rational design methodology. A comparative study between the application of McLeod method and New Zealand method is performed to evaluate the best chip seal design methodology for adoption into the State chip seal specifications. The results will also determine if the macro-texture based New Zealand chip seal performance specification is applicable for Oregon chip seals.