Bond Properties of GFRP Laminate with Heat-Damaged Concrete

Abstract

Concrete, when exposed to elevated temperatures, undergoes deterioration and loses much of its strength. The strengthening of heat-damaged concrete is possible with the help of external reinforcing materials such as fiber-reinforced polymers (FRPs). The strength of FRP-strengthened flexural concrete members depends on the bond between the FRP and the concrete. The purpose of this experimental study was to investigate the behavior of the bond between the glass fiber-reinforced polymer (GFRP) laminate and the heated concrete using a single-shear test (SST). The specimens were initially heated to temperatures of 200, 400, 600, and 800°C. The heat-damaged specimens were subsequently bonded with FRP sheets with various bond lengths (100, 150, and 200 mm). The test variables were bond length and elevated temperatures. The results show that bond strength increased with increasing bond length and noticeably decreased as temperatures exceeded 400°C. The thickness of the delaminated concrete layer with GFRP composite was less than 4 mm for the specimens subjected to temperatures less than 400°C. However, the thickness of the delaminated concrete ranged 4–25 mm in 600 and 800°C heat-damaged specimens. The ultimate bond stress was influenced by the bond length and increased as the bond length decreased. A model is proposed to estimate the bond strength between GFRP laminate and heated concrete.