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Glass Fiber Reinforced Polymer
DOWEL BAR
Glass Fiber Reinforced Polymer (GFRP) Dowel Bars have a number of advantages when used as load transfer devices for extended life pavement. The Achilles Heel of concrete pavement is the joint. Joint failure is often the result of corrosion of the steel dowel bar. Aslan 600 Dowels will not rust or corrode, locking a concrete joint together or causing spalling of the surrounding concrete. In addition, while providing the necessary shear capacity at the joint, the lower stiffness of the GFRP Dowel bars may reduce fatigue stresses in the concrete surrounding the dowel.
Aslan 600 GFRP Dowel Bars are also electromagnetically transparent and frequently used in toll collecdtion areas near inductance loops embedded in paving. Typically Aslan 100 GFRP Tie Bars are also use for longitudinal joints in conjunction with Aslan 600 Dowels.
The shear strength of the GFRP Dowels is measured in two ways, shear in bending and pure shear. The bending shear test used is a standard ASTM test placing the dowel bar in a three-point loading fixture. Also known as a short beam shear test.
In case of pure shear, a special test fixture is used to shear the dowel in two planes. The shear strength is determined from the double shear test.
Field Trials
In 1983, the Ohio Department of Transportation (ODOT) installed several alternative dowel bars for long-term durability performance studies in sections of Interstate 77 in Guernsey County and Ohio State Route 7 in Bellmont County. These dowel bars were produced with the same constituent materials as in the Aslan 600 GFRP Dowels. In 1998, the Market Development Alliance (MDA) of the composites industry organized the extraction and testing of samples of these dowel bars to determine their durability performance after 15 years of in pavement service.
These results show that the GFRP Dowel Bars were virtually unaffected by approximately 15 years of fi eld service and exposure.
GFRP Dowel Bars have been installed in Illinois, Iowa, Kansas, Minnesota, Ohio, Wisconsin, Colorado, New Yoir, New Jersey, Texas, Florida, California, Arizona, Hawaii, and Manitoba and many countries outside North America.
Performance of GFRP Dowels
The three design elements for dowels are spacing, length and diameter. Due to flexibility of the sub grade,
the load is not transferred by a single dowel but by a group of dowels. Tests performed at the University of Manitoba in Winnipeg Canada show the joint effectiveness of GFRP Dowels to be in the range of 86% to 100% effectiveness using a weak sub grade and 90% to 97% using a stiff sub grade. An ACPA criterion for successful joint load transfer is 75%. The research concludes, "GFRP dowels are a viable, corrosion free alternative to steel dowels." (ACI Structural Journal Vol. 98 No. 2, March-April 2001, Glass Fiber Reinforced Polymer Dowels for Concrete Pavements, D. Eddie, A. Shalaby and S. Rizkalla.)
Loose or Baskets
Aslan 600 GFRP Dowels are generally furnished loose. When supplied loose they may be used by dowel bar insertion machines or as part of a dowel bar retrofit system. Use in construction joints or drilled and epoxied into existing cold joints using a structural epoxy, such as MBT 1420, Unitex Propoxy 400 or DeNeef Denepox, is also appropriate.
Aslan 600 Dowels may also be furnished in a 100% non-metallic basket assembly, the DBB1500 series. The completely metal free basket allows for free flow of concrete between the dowels which helps maintain alignment during the pour. The basket has been tested for a vertical load in excess of 1500 lbs.
The DBB1500 series is very light weight. Individual support chairs are snap fit into #3 fiberglass rebar runners and the 1-1/2" x 18" smooth round GFRP Dowel Bars snapped into place. Basket assemblies are generally field assembled.
With GFRP Dowel Bars, there is no need to grease the dowels as the bond strength to concrete is sufficiently low to allow longitudinal movement of the concrete.
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