Final Report for Early-Opening-to-Traffic Portland Cement Concrete for Pavement Rehabilitation

Abstract

This report contains the background information, experimental design, results, analysis, and conclusions of the study conducted under NCHRP Project 18-04B, Durability of 'Early-Opening-to-Traffic' Portland Cement Concrete for Pavement Rehabilitation. Guidelines and recommendations for the design and construction of durable early-opening-to-traffic (EOT) portland cement concrete (PCC) mixtures for pavement rehabilitation were also developed in this study. As motorists become increasingly less tolerant of delays caused by pavement rehabilitation, state highway agencies (SHAs) have responded by adopting techniques that minimize the time of lane closure. One such technique is to use EOT rehabilitation strategies that allow work to be completed at night or during periods of low traffic. Generally, PCC used in these applications is expected to become strong enough to carry traffic within 6 to 24 hours after placement. But concerns have been raised that such high early strength materials lack durability, resulting in the need for additional lane closures to fix failing repairs. NCHRP Project 18-04B was conducted to evaluate the durability characteristics of EOT concrete to develop guidelines for materials, mixtures, and construction techniques that enhance long-term durability of EOT concrete for pavement rehabilitation. The research dealt with concrete mixtures that are suited for opening to traffic within (a) 6 to 8 hours and (b) 20 to 24 hours after placement and was limited to full-depth rehabilitation, such as a full-depth repair and slab replacement. In the course of the project, a review of literature was used to design an experiment that evaluated both field- and laboratory-prepared EOT concrete mixtures. In the experiment, 6- to 8-hour and 20- to 24-hour EOT concrete mixtures obtained from four states (Ohio, Georgia, Texas, and New York) were evaluated to determine typical mixture properties and performance characteristics. Also, a laboratory study was undertaken to produce and test 28 different EOT concrete mixtures (two replicates or batches were made for each mixture for a total of 56 batches). The testing included assessment of the properties of the fresh concrete, volume change, freeze-thaw durability, microstructural characterization, and the absorption/porosity of the concrete. The results were analyzed to draw conclusions regarding the durability of the mixtures and to form the basis for the guidelines. It is expected that the application of these guidelines will enable SHAs to better understand mixture design, proportioning, and construction practices that affect EOT concrete durability and to achieve longer-lasting EOT concrete repairs.