Chip Seal

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Research & Performance

NCHRP Synthesis 342 - Chip Seal Best Practices
Prepared By: Douglas Gransberg and David M.B. James

This synthesis report provides an overview of successful chip seal practices in the United States, Canada, and overseas. Although not meant to be an exhaustive study, it covers the spectrum of chip seal practice and presents, where possible, the state of the art, as reported in the literature and survey responses. The report presents ways to assist in the development and implementation of pavement preservation programs by identifying the benefits of using chip seal as part of a preventive maintenance program. Innovative and advanced chip seal programs from around the world were identified with respect to critical factors that can be incorporated by other transportation agencies. Approximately 40 best practices were identified in the areas of chip seal design methods, contract administration, equipment practices, construction practices, and performance measures. The increased use of chip seals for maintenance can be a successful, cost-effective way of using preventive maintenance to preserve both low-volume and higher-volume pavements.

Life Cycle of Pavement Preservation Seal Coats
Prepared By: Pedro Romero, Ph.D., University of Utah and Doug Anderson, Utah Department of Transportation

The use of preservation seals on asphalt pavements is a crucial part of any effective pavement management program. It is important to optimize the use of available budgets to extend the life of our pavements as much as possible. The nation’s highway system is one of our most valuable assets.

Analysis of the performance of surface treatments on Utah pavements indicates that Open Graded Surface Courses (OGSC) have an average life, based on skid resistance of almost 9 years and that Chip Seal Courses (CSC) have a significantly longer life.

Out of all the factors analyzed, traffic has the most significant effect on the performance of the treatment. Factors such as aggregate source and asphalt supplier were also investigated but lack of data prevented from reaching any significant conclusion.

Based on the relative cost of both treatments and the performance observed through this study, it is recommended that Utah Department of Transportation expand the use of CSC to certain roads with AADTs up to 20,000 vehicles and continue the existing procedure of using CSC in highway sections with AADTs below 5,000. It is also recommended that UDOT modified the existing policies and limit the use of OGSC where the running speeds are 55 mph or greater and AADTs are in excess of 25,000 vehicles. Medium volume facilities (5,000 to 25,000 AADT) should be sealed with treatments new to UDOT but proven in other states.

An initial cost analysis showed that the implementation of the changes suggested as part of this report will results in savings of over $2 million per year in the maintenance budget. Thus allowing for better use of resources while still serving the traveling public.