The main purpose of this study was to investigate the flexural behavior of high-ductility fiber-reinforced concrete (HDC) and propose a suitable method for evaluating flexural toughness. The flexural strength, deformation, and toughness of HDC were investigated through four-point bending tests with specimens of 40 × 40 × 160 mm. The test parameters were fiber volume fractions (0%, 1%, 1.5%, and 2%), water–binder ratios (0.24, 0.26, 0.29, and 0.32), and ages (28 d and 56 d). The experimental results showed that polyvinyl alcohol (PVA) fibers led to significant improvement in the flexural behavior of HDC due to its strain-hardening behavior and excellent crack dispersion capacity. The ultimate flexural strength of HDC with 2% PVA fibers of about 15.32 MPa showed an increase of up to 221%. The deformation and flexural toughness ratios were 23 times and 1.43 times higher, respectively, than the specimens without fibers. A simple and practical method for evaluating the flexural toughness of HDC was proposed, which solved many problems with the existing methods. This method made full use of the peak load, which overcame the difficulty of identifying the initial crack information, solved the insufficient deflection limit, and provided a more comprehensive and accurate evaluation by selecting characteristic points evenly distributed throughout the loading process.

To improve the thermal insulation properties and toughness of concrete, the glazed hollow bead (GHB) and polyvinyl alcohol (PVA) fiber reinforced cementitious composites (GPCC) were investigated by orthogonal test, which includes six GHB mass percentage (20%, 40%, 60%, 80%,100%, 120%), three PVA volume fraction (1%, 1.5%, 2%) and water binder ratio (0.26, 0.30, 0.34). Compressive, split tensile strengths and thermal conductivity of GHB-PVA reinforced cementitious composites (GPCC) were tested, and the mechanism of fibers was analyzed from a microscopic perspective. The results revealed that the thermal insulation will be significantly improved with the increased content of GHB, but the compressive and split tensile strength will be decreased simultaneously. No obvious effect was found by the PVA fiber addition on its strength indexes, and the presence of GHB will affect the bridging action of PVA fibers. The water binder ratio has more effect on strengths than thermal conductivity. Based on the mechanical performance rather than the thermal insulation analysis test, the optimal mix proportions were proposed: mass percentage of 40% GHB, a volume fraction of 1.5% PVA fiber, and 0.26 water-binder ratio. Moreover, the anchoring and bridging effect of PVA fibers will effectively balance the stress generated by the shrinkage of cement paste, and inhibits or even prevents the development of cracks. However, a certain number of tiny cracks will be formed near the GHB, and between GHB and PVA fibers, which will cause local stretching and peeling of PVA, and shattering inside the GHB with the increase of external force. The findings of this study can provide a useful reference for the application of an insulated-bearing material with GHB and PVA fiber.