Experimental and Analytical Studies of an Ultra-high Performance Concrete Beam Using Carbon Fiber Reinforced Polymer Bars

Abstract

Infrastructure degradation attributable to concrete deterioration and corrosion of reinforcing steel has been a long-standing challenge to the owners and engineers. This problem becomes more evident when concrete structures are subject to aggressively corrosive environments. The use of advanced materials such as ultra-high performance concrete (UHPC) and carbon fiber reinforced polymer (CFRP) bars has a strong potential to overcome this challenge and help build new infrastructure that is durable and sustainable. However, structural behavior of members using both UHPC and CFRP bars has not been studied thoroughly in the United States and overseas, and no codes or specifications are readily available for structural engineers to follow. This paper presented an initial attempt to explore this topic by addressing the bond behavior between UHPC and CFRP bars through pullout tests. The test results showed that the UHPC specimens exhibited gradually increased slippage after the peak load and demonstrated superior bond performance in comparison with the conventional concrete specimens. Flexural tests were also conducted to compare the structural behavior of two large-scale beams, which were made of conventional concrete reinforced by steel bars and UHPC reinforced by CFRP bars, respectively. Test results showed that the UHPC beam did not exhibit as much ductility as the conventional beam, as predicted. However, there was still sufficient warning of impending failure in a form of extensive cracking and substantial deflection attributable to the bridging effect of the steel fibers. Further, flexural strength analysis of the UHPC beam using CFRP bars was discussed satisfying strain compatibility and force equilibrium, which provided a guidance for structural engineers to design such members. The research approach adopted in this paper may be applicable to study UHPC beams using other types of FRP materials.