Feasibility of using geopolymers to investigate the bond behavior of FRP bars in seawater sea-sand concrete

Abstract

To fully exploit the application of marine resources in island engineering construction and to improve the durability of fiber-reinforced polymer (FRP) reinforced concrete structures, this paper explores the feasibility of using geopolymers as alternatives to ordinary Portland cement (OPC) to investigate the bond performance of FRP bars in seawater sea-sand concrete (SWSSC). Two types of FRP bars (i.e., glass-FRP and basalt-FRP bars) and three grades of concrete (C40, C50, and C60) were also considered. The experimental results indicated that the cracking or rupture of the FRP bars dominated the failure modes of the pull-out specimens when the compressive strength (fcu) of seawater sea-sand geopolymer concrete (SWSSGC) exceeded 50 MPa. The utilization of the geopolymer binders enhanced the splitting tensile strength (ft) of the concrete owing to the improvement of interfacial microstructures between the binders and the aggregates, which delayed the propagation of internal cracks in concrete, thereby effectually enhancing the bond behavior of FRP bars, especially its bond rigidity that defined by the slop of bond stress-curves at ascending stage. Compared with the cement-based SWSSC, there was approximately three times improvement in the initial bond stiffness for SWSSGC under the same concrete strength. Additionally, as the fcu of SWSSGC increased, the ft/fcu ratio was gradually declined, but the initial bond rigidity and the bond strength were improved. These results manifested that the combination of the FRP bars and SWSSGC is feasible, which can provide a promising approach for the application of geopolymers in SWSSC structures.