This paper investigates the effects of steel fiber and PVA fiber hybrid blending on the compressive strength ($f_{\mathrm{c}\mathrm{c}}$), splitting tensile strength ($f_{\mathrm{t}\mathrm{s}}$), compression energy ($W_{1.0}$), and shrinkage properties of concrete. It also establishes a multi-factor crack resistance index evaluation model based on the Analytic Hierarchy Process (AHP) to comprehensively evaluate the crack resistance of concrete. The results show that the steel–PVA hybrid fiber (S-PVA HF) further enhances $f_{\mathrm{c}\mathrm{c}}$, $f_{\mathrm{t}\mathrm{s}}$, the compression energy, and the shrinkage suppression properties of the concrete. The crack resistance of the steel–PVA hybrid fiber concrete (S-PVA HFRC) is the best when the proportion of steel fiber is 1.0% and that of the PVA fiber is 0.2%, and it increases up to 143% compared to the baseline concrete. The established concrete crack resistance evaluation model has a certain reliability.

This paper explores the impact of steel–PVA hybrid fibers (S-PVA HF) on the flexural performance of panel concrete via three-point bending tests. Crack development in the concrete is analyzed through Digital Image Correlation (DIC) and Scanning Electron Microscope (SEM) experiments, unveiling the underlying mechanisms. The evolution of cracks in concrete is quantitatively analyzed based on fractal theory, and a predictive model for flexural strength (PMFS) is established. The results show that the S-PVA HF exhibits a synergistic effect in enhancing and toughening the concrete at multi-scale. The crack area of steel–PVA hybrid fiber concrete (S-PVA HFRC) is linearly correlated with deflection (δ), and it further reduces the crack development rate and crack area compared to steel fiber-reinforced concrete (SFRC). The S-PVA HF improves the proportional ultimate strength (f_L) and residual flexural strength (f_R,j) of concrete, and the optimal flexural performance of concrete is achieved when the steel fiber dosage is 1.0% and the PVA fiber dosage is 0.2%. The established PMFS of hybrid fiber-reinforced concrete (HFRC) can effectively predict the flexural strength of concrete.

The effects of steel fiber length (l_f = 30 mm, 40 mm, 50 mm and 60 mm) and coarse aggregate maximum size (D_max = 10 mm, 20 mm, 30 mm and 40 mm) on fractural properties of steel fiber reinforced concrete (SFRC) was investigated. The results show that the fracture energy (G_f) of SFRC reaches its maximum when D_max increases to 30 mm, and it increases first and then decreases as lf increases, but it still has a significant increase compared to the control concrete. The G_f ratio increases first and then decreases as the l_f/D_max increases. The G_f of the SFRC fracture surface follows the same trend as the fractal dimension. The rational range of the l_f/D_max is 2.5–4 for the considerable strengthening effect of steel fiber on fracture performances of concrete with the D_max of 10 mm and 20 mm and 1.5–2.33 for that concrete with the D_max of 30 mm and 40 mm. The finite element analysis results are compared with the experimental results, and the results show that the fracture process of the finite element model is consistent with the experiment.