LABORATORY EVALUATION OF CONCRETE-FILLED GFRP DOWELS IN JOINTED CONCRETE PAVEMENTS

For decades, smooth, round, steel dowels have been used to transfer traffic wheel loads across the joints of concrete pavements. These dowels are subjected to shear and bending stresses due to thermal gradients in the pavement slabs in addition to the traffic loads. Over time, the concrete pavement joints become damaged due to the corrosion of the steel dowels as a result of the use of de-icing salts. As well, the small diameter, high strength, steel dowels create high bearing stresses in the concrete surrounding the dowels which causes the concrete to crush and spall locally. This eventually causes the dowels to become loose which is the major cause of pavement joint faulting. Dowel materials such as stainless steel, stainless clad, and glass-fibre reinforced polymer (GFRP) have been introduced in recent years as possible solutions to the corrosion problem. The size of the dowels has remained the same, typically 38 mm (1.5”) in diameter for high-trafficked roads, which does not solve the bearing stress problem and costs can be very high for stainless steel. In order to address both the corrosion and bearing stress problems, large-diameter concrete-filled GFRP tube dowels have been introduced. Experimental work at the University of Manitoba examined and compared the performance of four dowel types including 38 mm epoxy coated steel, 38 mm solid, pultruded GFRP dowels, and two sizes of concrete-filled GFRP tube dowels having diameters of 50.8 mm and 63.5 mm each. The dowels, which were cast in full-scale depth concrete slabs, were instrumented with strain gauges and small linear variable displacement transducers (LVDTs) attached to the dowel by small steel rods extending down through a small slot in the concrete. Behaviour of the dowels was evaluated based on measured displacements and performance over one million load cycles. Tests showed that the concrete-filled GFRP tube dowels exhibited considerably lower displacements and therefore, lower bearing stresses than the smaller 38 mm steel and pultruded GFRP dowels. After one million load cycles, the concrete-filled dowels and the concrete slab showed no signs of fatigue damage and exhibited great potential for use in jointed concrete pavements.