Durability Evaluation of Carbon Fiber –Reinforced Polymer Strengthened Concrete Beams: Experimental Study and Design

Abstract

This paper deals with the durability of the reinforced concrete (RC) beams externally strengthened with carbon fiber-reinforced polymer (CFRP) plates and fabrics under adverse environmental conditions such as 100% humidity, saltwater, alkali solution, freeze-thaw, thermal expansion, dry-heat, and repeated load cycles. The deflections, strains, failure loads, and failure modes of strengthened beams exposed to different independent environmental conditions and repeated load cycles are presented. To determine the design strength of CFRP-strengthened beams exposed to long-term environmental conditions, strength reduction factors associated with various independent environmental conditions are proposed. In addition, the failure modes and physical changes of the beams exposed to various independent environmental conditions were also examined. It is concluded that the long-term exposure to humidity is the most detrimental factor to the bond strength between CFRP plates and fabrics and RC beams. Beams strengthened with CFRP plates and exposed to 10,000 hours of 100% humidity (at 38 ± 2 °C) experienced an average of 33% reduction in their strength. The onset of delamination was the primary mode of failure for all of the test beams. Finally, a durability-based design approach is presented. The design approach appropriately demonstrates the evaluation of nominal and design moment strengths of the beam strengthened with CFRP plates and exposed to a 100% humidity condition.