The project produced guidelines to facilitate highway agencies' use of "early-opening-to-traffic" (EOT) concrete for pavement rehabilitation, thereby reducing pavement closure and accruing economic and environmental benefits. These guidelines address the proportioning, testing, construction, and other aspects of EOT concrete.

With increasing traffic in urban areas, motorists are becoming less tolerant of delays during pavement rehabilitation. To minimize delays, state highway agencies use EOT rehabilitation strategies that allow work to be completed at night or during periods of low traffic. Generally, portland cement concrete used in these applications is expected to become strong enough to carry traffic within 6 to 24 hours after placement. Rigorous requirements for mix design and strength development have usually been stipulated for EOT concrete applications, often with limited consideration given to materials and construction aspects that influence long-term performance and durability. Because much of the recent research on EOT concrete focused on its mechanical properties and limited research dealt with durability aspects of this type of concrete, there is a need to evaluate the durability of the concrete used in these applications and to recommend guidelines that address relevant aspects of EOT concrete to help achieve long-term performance, durability, and cost-effectiveness.

The research focused on durability aspects of EOT concrete used for full-depth rehabilitation (e.g., full-depth repair and slab replacement) and dealt with concrete mixtures that are suited for opening to traffic within 6 to 8 hours or 20 to 24 hours after placement. The research includes (a) a review and synthesis of information relevant to the materials and practices used for EOT concrete construction; (b) an evaluation of six in-service EOT concrete rehabilitation projects located in four states; (c) conduct of laboratory tests on a large number of concrete specimens involving a wide range of mixtures appropriate for use in EOT pavement rehabilitation; (d) conduct of statistical analysis of the data obtained from the field and laboratory evaluations; and (e) development of guidelines for the proportioning, testing, and construction of 6- to 8-hour and 20- to 24-hour EOT concrete.

The research concluded that while designing and constructing durable 6- to 8-hour and 20- to 24-hour EOT concrete is feasible, proportioning and constructing durable 6- to 8-hour EOT concrete is particularly challenging. It also highlighted the importance of ensuring an adequate entrained air-void system the need for conducting certain tests on actual job mixtures to account for potential adverse interactions between concrete constituents. NCHRP Report 540 contains the guidelines developed in this project. The agency final report is available online as NCHRP Web-Only Document 76.