Institute for Transportation

About the research

An increasing number of concrete overlay projects in Iowa and around the United States have used fiber-reinforced concrete (FRC) mixtures. Fibers provide residual strength to concrete mixtures, and concrete overlay design procedures currently assume that fiber reinforcement enhances fatigue life. A number of studies have suggested that fibers may offer a number of additional performance benefits to concrete overlays. This study conducted a field investigation of six different concrete overlay sites in Iowa. Three of these sites contained test sections with varying thickness and joint spacing designs, and with and without fiber reinforcement. The field investigation performed a variety of tests to measure properties such as joint activation behavior, load transfer, structural response, pavement smoothness, and curling and warping behavior. This test regime allowed for a broad characterization of many aspects of the behavior and performance of concrete overlays, both with and without fiber reinforcement. The results indicated that, to date, fiber reinforcement did not appear to have a significant impact on load transfer, smoothness, or curling and warping at these concrete overlay sties. However, the comprehensive testing regime provided a number of insights into other aspects of concrete overlay design and performance, both with and without fiber reinforcement. The bond between concrete and asphalt was particularly important, even when the overlays were not intentionally designed to bond to the underlying asphalt layer. Finally, the report for this project also contains an appendix detailing a separate investigation of the behavior of FRC pavements placed without transverse joints.