Insights on the interfacial bond behavior of modified resin-based GFRP strengthened coral aggregate concrete

Externally bonded reinforcement on grooves (EBROG) technique has been introduced to solve the debonding of glass fiber reinforced polymer (GFRP) composites from coral aggregate concrete (CAC) substrate. However, the resin type, bond length and GFRP thickness also affect the bond behaviors of GFRP-reinforced CAC structures. Therefore, the aim of this study was to comprehensively investigate the effect of these factors on the bond behaviors. To do so, CAC specimens reinforced by GFRP using EBR and EBROG techniques were subjected to double-shear bond tests. The failure modes, strain and local shear stress distribution, ultimate interfacial load capacity ( P u ) and averaged bond stress of specimens were discussed. Besides, the effects of groove characteristics (width, depth and spacing) on bond performance of specimens were revealed by finite element method. Furthermore, the bond mechanisms were analyzed from both adhesion and interlocking aspects. The results indicated that the interfacial shear stress could efficiently transfer from load-end to free-end of specimens by EBROG technique. In addition, the modified resin provided the mechanical interlocking force to specimens, resulting in the increase of bond performance. Furthermore, the thicker GFRP reduced the interfacial shear stress of specimens, avoiding the debonding of GFRP from CAC substrate. The failure mode of specimens was transformed to be controlled by CAC strength. The CAC specimens reinforced by thicker GFRP using EBROG technique showed a maximum increased in P u of 370.92 %. Besides, P u could further increase by 20.22 % through optimizing the groove characteristics.