Roundabout Construction Using Precast Concrete in Virginia

About the report:

Roundabouts are a special type of intersection that ensures continuous vehicle movement while maintaining slow and safe speeds. Many state departments of transportation are converting existing intersections into roundabouts, but roundabout construction can create significant traffic closures and disruptions. Thus, accelerated construction can be very beneficial in places where extended traffic closure is not practical or possible. Using precast concrete panels in roundabout construction can shorten closure times and create less disruption for the traveling public.

The Virginia Department of Transportation has constructed two precast roundabouts in the Richmond District—a mini roundabout on the I-195 South ramp at the Laburnum Avenue exit in December 2020 and a regular, full‑sized roundabout with an unpaved central island at the intersection of Hopkins and Kingsland Roads in July 2022. The panels were cast in New York and delivered to the jobsite for installation. The Laburnum Avenue roundabout was the first of its kind in the United States to be successfully completed and has performed satisfactorily since. The contractor was unfamiliar with this type of application but was able to complete both projects with weekend closures, thus minimizing weekday traffic disruptions. For comparison, the research team investigated five other roundabouts—four cast-in-place concrete and one asphalt truck apron with concrete curb containing rapid-setting cement. The roundabouts are constructed successfully using either precast panels or cast-in-place concretes and performing satisfactorily after at least a year of traffic exposure. The precast roundabout construction needs special attention to the base preparation, panel installation, and grouting. It is recommended that precast roundabouts be considered when short traffic disruptions are needed such that only weekend closures are permitted or when the supply of fresh concrete is of concern. Roundabouts with precast panels are expected to be more durable than the cast-in-place alternatives because the precast panels are cast in a controlled environment.

_{Disclaimer Statement:The contents of this report reflect the views of the author(s), who is responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Virginia Department of Transportation, the Commonwealth Transportation Board, or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. Any inclusion of manufacturer names, trade names, or trademarks is for identification purposes only and is not to be considered an endorsement.}

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