Behavior of reinforced concrete two-way slabs reinforced with carbon FRP bars under flexural loads

This study presents an experimental, numerical, and analytical investigation of the flexural behavior of two-way high-strength concrete (HSC) slabs reinforced with carbon fiber-reinforced polymer (CFRP) bars. Seven slabs with dimensions of 1500 mm × 1500 mm were tested, including one steel-reinforced reference slab and six CFRP-reinforced slabs with two thicknesses, 100 and 120 mm, and three CFRP reinforcement ratios. For the 100 mm slabs, increasing the CFRP reinforcement ratio increased the ultimate load by 13.8% and 24.3% relative to S100-CFRP1, while the corresponding increases for the 120 mm slabs were 31.1% and 48.0% relative to S120-CFRP1. Increasing the slab thickness from 100 to 120 mm enhanced the ultimate load by 27.7%, 47.2%, and 52.1% for the corresponding CFRP-reinforced specimens. A mechanically normalized comparison between the steel-reinforced reference slab and the CFRP-reinforced slab with the same nominal reinforcement ratio showed that the two specimens were not mechanically equivalent. The CFRP-reinforced slab had lower effective reinforcement stiffness but a higher strength-based mechanical reinforcement index, resulting in a higher ultimate load but lower deformation capacity. Crack observations confirmed flexural failure with more localized cracking in the CFRP-reinforced slabs. A nonlinear finite element model was developed in ABAQUS and validated against the experimental results, with an average ultimate-load prediction error of approximately 7.2%. Analytical predictions based on ECP 208-2019 and ACI 440.1R-15 showed average predicted-to-experimental ultimate-load ratios of 1.43 and 1.27, respectively, indicating that ACI 440.1R-15 provided closer estimates than ECP 208-2019 for the tested CFRP-reinforced slabs.