BACKGROUND
Bonded concrete overlays on asphalt (BCOA) pavements are a fast-growing pavement preservation and rehabilitation treatment in the United States. They have demonstrated their effectiveness as solutions for correcting areas with excessive rutting and shoving caused by slow, heavy loads, such as at intersections, as well as for a longer term overlay option on regular mainline pavements. Most BCOA projects consist of a 3- to 7-inch thick concrete overlay, with or without fibers, with panel sizes ranging from 4 to 12 feet.
Major advancements have been made recently in design methods for BCOA. However, there is still a need for information on key topics such as optimal BCOA mix design proportioning, construction practices, maintenance, repair, and rehabilitation, as well as a comprehensive review of overall performance. Current assumptions about anticipated design lives of BCOAs are derived from localized studies. Variables impacting design life include the previous condition of the existing pavement structure, the time dependent degree of bond between layers, overlay thickness, panel size, construction practices, environment, and traffic. Typical BCOA design lives are uncertain, and the timing and types of maintenance and repair activities need further study and definition.
Some highway agencies are reluctant to use BCOA because of a lack of experience and information. Thus, research is needed to determine expected BCOA performance. Other aspects of BCOA such as construction practices ("do’s and don’ts") and maintenance, repair, and rehabilitation requirements and procedures also need attention.
OBJECTIVES
The objectives of this research were to: (1) investigate factors that may impact BCOA performance, including, but not limited to, design procedures, specifications, mix design proportioning, construction practices, and maintenance and repair techniques; (2) document in-service BCOA performance through a literature review and survey; (3) conduct field surveys of selected BCOA projects; (4) develop representative performance prediction curves suitable for use in BCOA design selection based on the documented performance of a range of BCOA projects; and (5) compare actual versus predicted BCOA performance using current design procedures.
STATUS
This project is complete and the final report has been published as NCHRP Research Report 1007 Evaluation of Bonded Concrete Overlays on Asphalt Pavements. The appendices are available as NCHRP Web-Only Document 329.
