Structural response of reinforced, steel fiber reinforced and prestressed geopolymer concrete beams subjected to transverse loading

The workability of the geopolymer concrete mixes was evaluated in accordance with prevailing code of practice. Furthermore, regression analysis was carried out to establish correlations among the strength properties. Fly ash was considered as the primary binder, activated with NaOH and Na₂SiO₃ solutions. The beam mixes were selected based on trial combinations that achieved the highest compressive strength of 41.63 MPa at a water-fly ash ratio of 0.23. To investigate the structural performance, beams of generally reinforced, steel fiber reinforced and prestressed geopolymer concrete with comparable geometries were fabricated and tested under two-point loading. The results revealed that steel fiber reinforced and prestressed geopolymer concrete beams exhibited 14 and 32% higher ultimate strength, respectively, as compared with generally reinforced geopolymer concrete beams. Moreover, beam stiffness improved by 22% (steel fiber reinforced geopolymer concrete) and 25% (prestressed geopolymer concrete). All the beam types satisfied serviceability limits, with deflections below the code-specified span/250 ratio at cracking load. Strain measurements indicated reductions of 10% in steel fiber reinforced geopolymer concrete and 40% in prestressed geopolymer concrete relative to generally reinforced geopolymer concrete, with maximum strains of 0.036 (steel fiber reinforced geopolymer concrete), 0.035 (prestressed geopolymer concrete) and 0.030 (generally reinforced geopolymer concrete). Ductility ratios were observed to improve by 6−7% in both steel fiber reinforced geopolymer concrete and prestressed geopolymer concrete beams. Crack analysis revealed that the flexural failures were predominant in generally reinforced and steel fiber reinforced geopolymer concrete beams, while prestressed geopolymer concrete beams exhibited shear-dominated failures with diagonal tension cracks.