The influence of graphene oxide (GO) and polyvinyl alcohol (PVA) fiber on the mechanical performance, durability, and microstructure of cement-based materials was investigated in this study. The results revealed that compared with a control sample, the mechanical strength and durability of cement-based materials were significantly improved by adding PVA fiber and GO. The compressive and flexural strength at 28 d were increased by 30.2% and 39.3%, respectively. The chloride migration coefficient at 28 d was reduced from 7.3 × 10⁻¹² m²/s to 4.3 × 10⁻¹² m²/s. Under a sulfate corrosion condition for 135 d, the compressive and flexural strength still showed a 13.9% and 12.3% gain, respectively. Furthermore, from the Mercury Intrusion Porosimetry (MIP) test, with the incorporation of GO, the cumulative porosity decreased from more than 0.13 cm³/g to about 0.03 cm³/g, and the proportion of large capillary pores reduced from around 80% to 30% and that of medium capillary pores increased from approximately 20% to 50%. Scanning electron microscope (SEM) images showed a significant amount of hydration products adhering to the surface of PVA fiber in the GO and PVA fiber modified sample. The addition of GO coupling with PVA fiber in cement-based materials could promote hydration of cement, refine the microstructure, and significantly improve mechanical strength and durability.

To characterize the material state and residual reactivity of long-service dam concrete, concrete cores extracted from the Lushui Reservoir Dam after more than 60 years of service were investigated. Their long-term macroscopic properties were evaluated, and the hydration products and microstructural features of the aged binder were characterized using X-ray diffraction, thermogravimetric analysis, scanning electron microscopy/energy-dispersive spectroscopy, and mercury intrusion porosimetry. The residual hydration capacity of the aged binder was further assessed through hydration heat and mortar strength tests. The results showed that the compressive strength of the concrete cores was mainly distributed within the range of 20–40 MPa, while the splitting tensile strength was mainly distributed within the range of 1–3 MPa, indicating that the concrete still retained relatively good basic mechanical properties after more than 60 years of service. The resistance to chloride ion penetration was generally favorable, whereas the frost resistance was relatively poor. The aged binder still contained identifiable Ca(OH)₂, AFt, C-S-H, and CaCO₃, and the local binder skeleton and aggregate–paste interface remained relatively stable. The residual hydration capacity of the aged binder was approximately 14–17%, indicating that the binder system had not become completely inert and still retained measurable residual reactivity. These findings provide a useful reference for evaluating the material state of long-service hydraulic concrete.