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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
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Publication Number: FHWA-HRT-06-106
Date: September 2009
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).(4)
The main objectives of this study were as follows:
Details of laboratory tests conducted at West Virginia University (WVU) structural laboratory were as follows:
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:
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Topics: research, infrastructure, pavements, concrete, design, jointed, fiber-reinforced polymer, FRP, dowels
Keywords: research, infrastructure, pavements, concrete, design, GFRP, glass fiber-reinforced polymer, FRP dowel, JPCP, jointed plain concrete pavement, relative deflection, joint efficiency, dowel