Many bridge columns in Michigan are damaged by chloride contamination resulting in the corrosion of the steel reinforcement, and swelling and spalling of the concrete and use of the bridges is typically continued. This in itself may not be a serious problem since most columns in Michigan are over-designed and the loss of strength is not a significant issue. However, the lack of any method to minimize or prevent corrosion of the steel results in continued deterioration and unsightly columns. Polymer composite (also known as fiber-reinforced polymer or FRP) jackets offer a possible remedy to this problem. They offer a rapid repair technique with the potential to enhance the longterm durability and compression strength of damaged columns due to the confinement that is provided when fibers are oriented in the hoop direction. Fibers oriented in the vertical direction can enhance the bending strength.; Experiments were conducted to assess the effects of using FRP wraps with fibers oriented in the hoop direction for rehabilitating corrosion-damaged columns. Issues that were explored are: (1) effect of freeze-thaw and wet-dry cycles on the properties of FRP panels; (2) freeze-thaw durability of concrete square and cylindrical specimens wrapped with glass and carbon FRP and subjected to an internal expansive force; and (3) effect of wrapping on the rate of corrosion in an accelerated corrosion test.; The results of the freeze-thaw experiment indicate that freeze-thaw cycles have no statistically significant effect on the compressive strength of glass and carbon wrapped specimens. For round specimens, glass and carbon wraps increased the strength by a factor of about 2.3 and 2.6, respectively. For square specimens, glass and carbon wraps increased the strength by a factor of 1.4–1.5. Freeze-thaw conditioning generally reduced the longitudinal failure strain of wrapped specimens.; The square wrapped specimens had lower compressive strength compared to the round specimens, even though the cross sectional area of the square prisms is higher than that of the round cylinders. This is due to the reduced confinement provided by the wraps for square cross sections and stress concentrations that develop at the corners. Wrapped square prisms always failed by rupture of the wrap at a corner. A reduction of approximately 30% to 40% in failure stress was noted between round and square wrapped specimens.; The results of the accelerated corrosion experiment indicate that wrapping reduced the corrosion depth in the reinforcing bars by 46% to 59% after 190 days of testing. Both glass and carbon wraps are equally effective in slowing down corrosion. Although unbonded wraps do reduce stress concentrations in the FRP, they are less effective in reducing the corrosion rate than the bonded wraps. It is postulated that this is due to the ingress of water along the unbonded FRP-concrete interface. Wrap strains for bonded specimens with both types of wraps tend to level off with time indicating that corrosion slows down significantly after some time.
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