Evaluation of Corrosion Resistance of Steel Dowels Used for Concrete Pavements

In concrete pavements, steel dowels are exposed to a particularly aggressive environment that leads to depassivation and greatly reduces the corrosion initiation stage. Aggressive agents such as chlorides and $\mathrm{C}{\mathrm{O}}_2$ have easy access to the dowels through pavement joints and, consequently, the corrosion performance of the system depends largely on the properties of the steel dowel being used. This study investigates the corrosion performance of several types of steel dowels embedded in concrete and subjected to accelerated corrosion by exposure to 3.5% NaCl solution for $18\text{months}$ . Seven types of dowels were tested: bare carbon steel, stainless steel clad, grout-filled hollow stainless steel, microcomposite steel, carbon steel coated with bendable epoxy, and carbon steel coated with nonbendable epoxies. Half-cell potential, polarization resistance, visual inspections, and microscopic investigations by scanning electron microscopy were carried out to evaluate their corrosion performance. Results show that microcomposite steel dowels exhibit greater resistance to corrosion propagation than carbon steel dowels, but lesser than stainless clad and stainless hollow bars. In epoxy-coated bars, corrosion occurred at a few localized defective areas, generally at holidays and edges of bar ends. No significant difference was observed between nonbendable and bendable epoxy-coated dowels.