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Publication Number: FHWA-HRT-06-106
Date: September 2009

Design and Evaluation of Jointed Plain Concrete Pavement With Fiber Reinforced Polymer Dowels

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CHAPTER 1. INTRODUCTION

GENERAL REMARKS

U.S. highways and roads made of jointed plain concrete pavement (JPCP) use load transfer devices, called dowels, across joints of a series of contiguous concrete slabs. Joints allow the movement and deformation of pavement to occur under mechanical loading and thermal variations. Joints may either be parallel to traffic (longitudinal joints) or perpendicular to traffic (transverse joints). Typical problems of jointed concrete pavement without an effective load- transfer device include faulting, pumping, and corner breaks.

As the American Association of State Highway and Transportation Officials (AASHTO) reported, pavement joints supported with dowels have a longer service life than joints without dowels.(1) Over time, traffic traveling over a joint may crush the concrete surrounding the dowel bar and cause voids due to excessive bearing stresses between the dowel and surrounding concrete. Concrete crushing may take place due to stress concentration where the dowel contacts concrete at the joint face directly above and below the dowel. Looseness of dowel support can decrease the load transfer efficiency (LTE) across the joint and accelerate pavement damage.(2)

Corrosion of the dowel bar can potentially bind or lock the joint. When locking of the joint occurs, no thermal expansion is allowed, and new cracks parallel to the joint are formed directly behind the dowel bars in the concrete. As temperature decreases, contraction of the concrete widens the new cracks, leading to reduction of load transfer. Once there is no load transferred across the joint, the load is then transferred to the subgrade, and differential settlement occurs in the adjacent slabs. Differential settlement of the adjacent slabs creates uneven surface and discontinuity at the joints, making vehicle travel uncomfortable and leading to slab repair or replacement.

Currently, steel dowels, typically epoxy coated with a diameter of 2.54 or 3.81 cm (1.0 or 1.5inches) and length of 45.72 cm (18 inches), are widely used in JPCP. However, this coating is usually nicked or scraped before installation, leading to dowel corrosion and deterioration (figure 1). Fiber reinforced polymer (FRP) dowel bars, which are resistant to corrosive environments, can be used as effective load transfer mechanisms in JPCP. Currently, polymer matrix composites such as FRP are being used in a broad range of structural applications within the aerospace, automotive, marine, and construction industries due to their superior strength-to-weight ratio and high corrosion resistance.(3)

For this research, response of concrete pavement with FRP dowels was investigated through laboratory experiments and field implementation.

Figure 1. Photo. Exposed failures with rusted dowel bars (Washington State Department of Transportation Pavement Guide). This photo shows a portion of the jointed concrete pavement which is excavated to show two rusted, corroded steel dowel bars approximately at the mid-height of the slab cross section and spaced apart by 30.48 cm (12 inches).

Figure 1. Photo. Exposed failures with rusted dowel bars (Washington State Department of Transportation Pavement Guide).(4)

OBJECTIVES

The main objectives of this study were as follows:

  • To evaluate 3.81-cm (1.5-inch)- and 2.54-cm (1.0-inch)-diameter FRP dowel bars spaced at different intervals as load transferring devices in JPCP under HS25 static and fatigue loads and to compare their response (relative deflection (RD) and LTE) with JPCP consisting of steel dowels under laboratory and field conditions.
  • To evaluate the performance (strain and deflection) of JPCP rehabilitated with FRP and steel dowels.
  • To model FRP and steel dowel response and that of the pavement in terms of dowel maximum bending deflection, RD, and bearing stress.

SCOPE

Details of laboratory tests conducted at West Virginia University (WVU) structural laboratory were as follows:

  • Two jointed concrete slabs with 3.81-cm (1.5-inch)-diameter FRP dowels and 30.48-cm (12-inch)-slab depth were tested under static loads during preliminary static load investigation.
  • Five jointed concrete slabs with 3.81- and 2.54-cm (1.5- and 1.0-inch) steel and FRP dowels with spacings of 30.48 and 15.24 cm (12 and 6 inches) were tested under static and fatigue loads corresponding to HS25 load and 1.5 times HS25 load. The slab depth was 27.94 cm (11 inches) for all five slabs, similar to field installation depth.
  • Using identical slab thickness, fc', joint depth, and joint width, the pavement performance (LTE, RD, and dowel strain) with FRP and steel dowels was evaluated with respect to the following:
    • Dowel diameter.
    • Dowel spacing.

FRP dowel bars were field installed in new highway JPCP construction on Route 219, Elkins, WV. Both 3.81- and 2.54-cm (1.5- and 1.0-inch)-diameter FRP dowels were installed in the field, and the dowel spacings that were used were 15.24, 20.32, 22.86, and 30.48 cm (6, 8, 9, and 12 inches). Two field tests were conducted, and results were analyzed and are discussed in this report.

FRP dowel bars with 3.81-cm (1.5-inch) diameters were installed for pavement rehabilitation near the intersection of Routes 857 and 119, University Avenue, Morgantown, WV. Dowel strains due to regular traffic were analyzed and are discussed in this report.

Analysis and discussions corresponding to theoretical calculations are provided for four different examples of pavements with FRP and steel dowels in terms of dowel diameter, spacing, dowel material properties, joint width, and base material properties.

The remainder of this report is organized into the following chapters and appendices:

  • Chapter 2 deals with the literature review.
  • Chapter 3 describes materials and laboratory test setup used in this research.
  • Chapter 4 discusses experimental results from laboratory tests.
  • Chapter 5 presents field installation, field load test results, and discussions.
  • Chapter 6 presents theoretical evaluations.
  • Chapter 7 provides the summary and conclusions of this research, including suggestions for future research.
  • Appendix A describes a preliminary test on timber ties consisting of an FRP dowel as the load transfer device.
  • Appendix B analyzes and evaluates the effects of FRP dowel shear modulus on pavement RD.
  • Appendix C describes the details of burnout tests for determining fiber weight fraction (FWF) and fiber volume fraction (FVF) of FRP dowels with 2.54- and 3.81-cm (1.0- and 1.5-inch)diameters.

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