Ultrathin Overlays: Standing the Test of Time

In 1994, the Iowa Department of Transportation, in conjunction with the Federal Highway Administration, constructed an 11.6-km (7.2 mi) segment of ultrathin overlay on a section of portland cement concrete pavement in central Iowa. The project included variations in base preparation, slab depth and size, use of fibers, and consideration for joint sealing. The project was developed for 5 years of research monitoring, at the end of which the department decided to extend the evaluation for 5 years and to investigate the potential for repair methods of damaged panels. The project has survived the 10-year research window, and continues to perform well. The attributes that make this a good design are included in the paper for others to apply in the consideration of ultrathin surface restoration projects.