Dowel bars corrosion in concrete pavement

To study the effectiveness of sealants in reducing chlorides and water intrusion into pavement joint openings, nine 122 × 91 × 20 cm concrete slabs were fabricated. One slab was cast without a joint and was used as a control, two were cast with non-sealed joints, and the other six were cast with joints that were sealed, after the slabs were cured, with either type A (low modulus silicone) or type B (polyurethane) sealant, which are one-component rigid pavement joint sealants. Three dowel bars, used for load transfer, were installed below the joint at the mid-thickness of each slab. Two types of dowels were used: epoxy-coated and uncoated. A joint and crack beneath it were formed at the middle of the slab to simulate field conditions. To accelerate dowel bar corrosion and to examine pavement joint sealant effectiveness in abating chloride intrusion, the slabs were exposed to alternate ponding cycles of 6% sodium chloride solution (3 days of ponding and 4 days of drying). The corrosion progress was monitored by measuring corrosion current density using a three-electrode linear polarization device. Also, chloride contamination was measured by collecting powdered concrete samples from each slab at four different depths to determine the chloride concentration profile. The corrosion current density and chloride contents over a period of 18 months were analyzed. The results show that the unjointed slab has a higher resistance to chloride penetration, followed by jointed slabs sealed with type A sealant, then jointed slabs sealed with type B sealant. In addition, the performance of epoxy-coated dowel bars in abating corrosion was better than that of uncoated dowels.