Interfacial bond strength of glass fiber reinforced polymer bars in high-strength concrete

This paper presents the results of an experimental study on the interfacial bond strength of glass fiber reinforced polymer (GFRP) bars in high-strength concrete cube. The experimental program consisted of testing 54 concrete cube specimens prepared according to CSA S802-02 standard. Two main parameters were considered in the experimental investigation: the compressive strength of concrete (from 25.6 MPa to 92.4 MPa) and the type of rebar (steel, sand-coated GFRP, and helically wrapped GFRP). The test results showed that the interfacial bond strength of the GFRP bars increased as the compressive strength of concrete increased. However, the increasing rate of the bond strength of the GFRP bars with respect to the concrete strength was much smaller than that of the steel bars. The concrete specimens were sawn in half after the test for a closer investigation of the actual mode of bond failure. Visual examination of the specimens showed that bond failure of the steel bar was caused by concrete crushing against the face of the ribs, while bond failure of the GFRP bars occurred not only in the concrete but also in the bars by delamination of the resin-rich outer layer from the fiber core. The average area of the delaminated resin-rich layer of the GFRP bar increased with increasing compressive strength of concrete.