The National Concrete Pavement Technology Center (CP Tech Center) at Iowa State University has released significant findings from a comprehensive study on fiber-reinforced concrete (FRC) overlays—highlighting their potential to enhance pavement performance and inform future design standards. Iowa has increasingly adopted synthetic macrofibers in recent projects. These fibers, mixed directly into fresh concrete, aim to improve durability and crack resistance—especially in thin overlay applications. Under the leadership of CP Tech Center director and former ISCP Board member Dr Peter Taylor and research engineer Dan King, the study analyzed 37 overlay test sections, varying overlay type, thickness, transverse joint spacing, fiber dosage, and geotextile use.
The main findings of the study are:
- Reduced Cracking: FRC sections exhibited significantly fewer cracked slabs than non-fiber counterparts, particularly preventing mid-slab transverse cracking in overlays with extended joint spacing
- Joint Behavior: Joint activation reached 100% in almost all sections with 9 ft spacing, while those ≤6 ft showed less activation. Still, the presence of unactivated joints did not negatively impact performance
- Load Transfer & Smoothness: No measurable improvements were found in joint load transfer efficiency, pavement smoothness, or curling/warping behavior due to fibers
- Bonded Overlay Benefits: Concrete overlays on asphalt (COA) demonstrated enhanced structural capacity and load transfer, regardless of fiber inclusion—even when not explicitly designed as bonded overlays
Get the full report here.