Iowa Highway 105

This project is a 5-mile-long topping over existing deteriorated asphalt overlay with a concrete pavement base. Mitchell County agreed to a .8-mile test section in the middle of the Highway 105 project to investigate thickness and joint-space benefit opportunities courtesy of fiber reinforced concrete (FRC). Half of the test section was placed at 4” thick with the remainder at the conventional 6” thickness. For both segments, four joint-spacing options were used in 500 ft. long sections: 6’ x 6’, 12’ x 12’, 12’ x 15’, and 12’ x 20’; both plain (unreinforced) sections and FRC sections (FORTA-FERRO^®) were placed in-line. The fiber was added to the aggregate weigh-hoppers and then mixed uniformly with a portable central-batch mixing system. Pavement surface treatment included a wet-burlap drag and highway tining.

Over the next 2 years, the sections will be analyzed by the CP Tech Center using nondestructive sonar test devices to determine whether mid-panel cracks and/or joint-activation have occurred. The research findings will be used by Iowa’s city, county, and DOT engineers to choose the optimum longitudinal and transverse joint spacing in thin concrete overlays based on different variables. This project represents a rare opportunity to prove the merits of FRC in real-world, and real-traffic conditions.