High Performance Concrete Pavements
CHAPTER 14. IOWA 5 (Iowa 330, Melbourne)
In 2002, the Iowa DOT, in conjunction with Iowa State University, constructed concrete pavement test sections containing elliptical fiber-reinforced polymer (FRP) dowel bars. The test sections are located on Iowa 330, just west of Melbourne, Iowa (see Figure 40). The primary advantage of FRP dowels over conventional steel dowels is that they are not susceptible to corrosion. In addition, the benefits of an elliptical shape over circular are the reduction of bearing contact stress between the concrete and the bar. This project provides the opportunity to evaluate the performance of elliptical FRP dowels compared to both round and elliptical steel dowels installed on the same highway project.
Figure 40. Location of IA 5 project.
The goal of this project is the evaluation of the elliptical FRP dowels and elliptical dowel bar baskets to provide for transfer of load across the concrete pavement joints (Cable, Porter, and Guinn 2003).
Project Design and Layout
The elliptical FRP dowel bars used in this project are 457-mm (18-in.) long. The major and minor axes have dimensions of 57.15 and 49.28 mm (2.25 and 1.94 in.), respectively (Cable, Porter, and Guinn 2003). Dowel bars were placed in the northbound lanes at 30 joint locations, each 6 m (20 ft) apart. Three different dowel bar spacings (254, 305, and 381 mm [10, 12, and 15 in.]) were used. Figure 41 illustrates the layout of the dowel bars (Cable, Porter, and Guinn 2003).
Figure 41. Layout of dowel bars on IA 5 project.
The use of FRP material caused an inability to use the conventional method of welding steel dowel bars to the baskets. Therefore, the dowels were attached to the baskets using plastic ties and epoxy (Cable, Porter, and Guinn 2003). Special care was taken to make sure that, when dried, the epoxy was strong enough to hold the bars in position during the concrete placement, yet brittle enough to crack and allow the bars to move in the longitudinal direction after the concrete had set (Cable, Porter, and Guinn 2003).
To determine the stresses on the dowel bars at different spacings, one dowel bar from each of the 254-, 305-, and 381-mm (10-, 12-, and 15-in.) spacings was fitted with eight strain gauges. The strain gauge positions, as shown in Figure 42 (Cable, Porter, and Guinn 2003), were chosen to be the same as the strain gauges placed on the coinciding elliptical steel dowel bar project to facilitate a comparison between the two types of bars.
Figure 42. Location of strain gauges on elliptical FRP dowel bar.
State Monitoring Activities
The research team is monitoring the performance of these test sections for a period of 5 years. Visual distress surveys, joint opening and joint faulting measurements, FWD tests, and profile measurements are being conducted twice a year (spring and fall). Load testing using a loaded Iowa DOT tandem axle truck was conducted in fall 2002 and winter 2003 and will be conducted in the future only as long as the wiring to the test bars continues to function.
The following conclusions were drawn from this project during the construction process:
- The elliptical FRP dowels can be placed on metal baskets and successfully placed in concrete pavements.
- Testing of the FRP dowel locations indicates no specific difference with the steel dowels on an adjacent project.
Points of Contact
Iowa Department of Transportation
800 Lincoln Way
Ames, IA 50011
Max L. Porter
Iowa State University
Center for PCC Pavement Technology
2901 S Loop Drive, Suite 3100
Ames, IA 50010-8632
Cable, J. K., M. L. Porter, and R. J. Guinn. 2003. Field Evaluation of Elliptical Fiber Reinforced Polymer Dowel Performance - Construction Report. Iowa State University, Ames.