Behavior of GFRP Reinforcing Bars Subjected to Extreme Temperatures

Corrosion of steel reinforced concrete members has stimulated the research on fiber-reinforced polymers (FRP) to be used as an internal reinforcement for concrete structures. The behavior of glass fiber-reinforced polymer (GFRP) reinforcing bars subjected to extreme temperatures is very critical for applications in North America, especially in Canada. There is a high demand for experimental studies to investigate the thermal stability of strength, along with the ultimate elongation, and modulus of GFRP bars. This paper evaluates the variation of mechanical properties of sand-coated GFRP reinforcing bars subjected to low temperatures (ranging from 0 to -100 degrees C) and elevated temperatures (ranging from 23 to 315 degrees C). Tensile, shear and flexural properties are investigated to get an overview of the thermal stability of mechanical properties of GFRP bars subjected to large variations of temperatures. Microstructural analyzes using scanning electronic microscopy (SEM), physical measurements by thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC), are also conducted to investigate the deterioration of fiber, matrix, and the fiber/matrix interface due to extreme temperatures. Increase of mechanical properties due to the matrix stiffness at lower temperatures, is also investigated. On the other hand, at very high temperatures, nearing about the glass-transition temperatures of the polymer matrix, the mechanical properties, especially the stiffness and the strength of the composites are decreased considerably.