Evaluation of alternative dowel bar materials and coatings : executive summary report.
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2011-01-01
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Edition:Executive summary report.
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Abstract:The inclusion of steel dowel bars to transfer forces across sawed or formed transverse joints from one concrete pavement slab to another while permitting expansion and contraction movements of the concrete has been a basic design practice in most U.S. state departments of transportation (DOTs) for many decades. However, corrosion of the steel dowels remains a common problem, especially in states that use salt and other caustic deicing chemicals for snow and ice control. Significant corrosion reduces the effective diameter of the dowel bar in the joint, often to the point where the dowel bar will fail in shear when loaded, resulting in faulting of the pavement slab. Furthermore, the corrosion can also “lock” the dowel bar into the concrete, preventing movement of the concrete during expansion and contraction and thereby leading to the development of cracking in the adjoining slabs. In the mid-1970s, state DOTs began to require that steel dowel bars be coated with epoxy or other materials to prevent corrosion, and epoxy-coated dowels became the standard for most states. Recently, a number of different alternative dowel bar materials have emerged, seeking to combine effective load transfer capabilities with enhanced corrosion resistance. While the corrosion resistance of some alternative materials have been well documented in laboratory examinations, other performance characteristics affecting service life remain to be fully evaluated, particularly in representative field installations and over meaningful time periods.
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