Experimental evaluation of the tensile bonding strength of the basalt fiber-reinforced polymer-concrete interface

The bonding performance of basalt fiber-reinforced polymer and concrete substrate has a significant effect on the reliability of externally strengthened existing concrete structure, due to being the most vulnerable element to failure in this fiber-reinforced polymer-concrete strengthening system. Its failure can result in the failure of the whole structure. Although many previous researchers have been interested in the tensile bonding strength of carbon fiber-reinforced polymer and glass fiber-reinforced polymer-concrete interface, that of basalt fiber-reinforced polymer-concrete interface has been very limited. Thus, the objective of this study is to experimentally assess the tensile bonding strength of the basalt fiber-reinforced polymer-concrete interface. The effects of high temperature, freezing-thawing cycles, type of resin, and concrete crack widths on the tensile bonding strength are also investigated. The pull-off experiment is conducted according to ASTM D7522/D7522M-15. A total of 205 core specimens of 50 mm diameter and 10 mm depth were taken from 41 concrete beams. The experimental results illustrate that both freezing-thawing and high-temperature condition have a substantial effect on the bonding strength of the basalt fiber-reinforced polymer-concrete interface. Bonding strength was decreased within the range of about 9%-30% when the number of freezing-thawing cycles increases from 100 to 300; likewise, it was decreased up to 30% when the exposure temperature rises to 200 degrees C. Also, the specimens which were repaired to close their cracks by epoxy resin had no significant effect on the bonding strength of basalt fiber-reinforced polymer-concrete interface, when the specimens had crack width of less than 1.5 mm.