Effect of GFRP rebars and polypropylene fibers on flexural strength in high-performance concrete beams with glass powder and microsilica

Considering the benefits of GFRP rebars and their lighter weight compared to steel rebars and the sustainability of polypropylene fibers, GFRP rebars and polypropylene fibers are investigated as sustainable materials replacements for steel rebars in high-performance concrete (HPC). This study employs micro silica (10 wt% of cement) and wastes glass powder (25 wt% of fine grains) to increase the concrete's strength and achieve HPC. There are four compression specimens and six flexural specimens created. The flexural specimens comprise those without reinforcing bars, those with steel reinforcing bars, those with GFRP reinforcing bars, and those with a hybrid usage of GFRP reinforcing bars with varying fiber ratios. Utilizing only GFRP reinforcing bars produces concrete beams with a lower flexural strength than using steel reinforcing bars. Simultaneous usage of 1.5% polypropylene fibers and GFRP rebars achieves the same flexural strength as steel rebars while decreasing the beam's weight by about 4% and minimizing preparation costs and CO2 emissions. The addition of 0.5% polypropylene fiber enhanced the flexural strength of concrete reinforced with GFRP rebars by about 6%, while the addition of 1.5% fiber increased the compressive strength by 20%. Glass, micro silica, fibers, and rebars are among the sustainable materials employed in this study. Consequently, the use of GFRP reinforcing bars decreases CO2 emissions by 43 percent. Additionally, employing micro silica at 10 wt% of cement decreases CO2 emissions by 95,4 kg per ton of cement.