Effect of Fiber-Reinforced Polymer Wrapping on Concrete Chloride Penetration and Concrete Cover

Abstract

The objective of this study was to investigate the effect of fiber-reinforced polymer (FRP) wrapping on chloride penetration in concrete and the possible associated effects on concrete clear cover requirements. FRP wrapping used to retrofit concrete structures offers a high resistance to chemical solutions. This study established levels of chloride penetration in carbon- and glass-based FRP-wrapped concrete specimens through a saline ponding test, based on ASTM C1543 and ASTM C1152 procedures. The specimens were exposed to a sodium chloride solution for 6 weeks, at the end of which powder samples were collected from various depths to determine the level of chloride penetration. Results indicated that both types of FRP wrapping resulted in significant reductions in chloride penetration in the concrete. The decrease in chloride content was maximum (22%) near the surface and decreased with penetration depth. The American Concrete Institute 318 building code allows for a reduction of required concrete covers if alternative forms of protection from earth or weather are provided. Equivalent concrete covers for the FRP-wrapped samples were determined that would result in similar chloride ingress and possible steel corrosion. The cover reductions can range from 16% to 26% for beams and 44% to 50% for slabs, based on the FRP type. The reduced equivalent covers can lead to increased load capacity of the concrete members. Likewise, the FRP application may be used to satisfy existing unacceptable clear cover values in older structures compliant to current code provisions.