Investigation on Shear Strength of Fiber Reinforced GPC Exposed to Elevated Temperatures

Geopolymer concrete (GPC) is a novel and sustainable building material that tends to be more brittle than that of conventional concrete (CC). As such, exposure to fire makes the GPC even more brittle. Fortunately, this brittleness can be reduced by adding fibers, which improves its homogeneity and shear strength in the interfacial region. The present work investigates the influence of high temperatures on the interfacial shear strength of fiber-reinforced GPC (FGPC) and hybrid GPC (HGPC) using shear (push-off) samples exposed to the ISO 834 fire curve. The GPC is developed using two alkaline binders at a 10 M NaOH concentration. A total of six types of mix proportions were used: normal GPC mix without fibers, FGPC mix with basalt fiber (BF), crimped steel fiber (SF) and polypropylene fiber (PF), and HGPC mixes with a combination of SF and BF and with a combination of SF and PF. After 30 and 60 min of heating, the highest residual compressive strength (CS) and residual shear strength (SS) are observed for specimens with BF, and lower residual CS and SS are observed for GPC-PF and GPC mixes. After 90 and 120 min of heating, the BF and SF + BF exhibited almost similar residual CS and residual SS, whereas the PF had the least residual compressive and residual shear strengths.