In this work, an accelerated non-uniform corrosion method controlled by time and current was employed to fabricate power-on accelerated corrosion specimens of hybrid steel fiber-reinforced concrete (HSFRC) gradient beams. Experimental research was conducted to investigate their impact resistance, revealing the dynamic response patterns of these gradient beams with varying steel fiber contents. By analyzing the evolutionary characteristics of impact load, displacement, energy dissipation, equivalent impact bearing capacity, and dynamic amplification factor, the influence of steel fibers with different sizes and contents on the bearing capacity degradation and mechanical properties of HSFRC gradient beams under the same corrosion conditions was clarified. The synergistic enhancement mechanism of multi-scale steel fibers in the beams was elucidated, highlighting the complementary effects of long fibers and short fibers at different stages of material damage. Results show that the incorporation of steel fibers can effectively improve the impact resistance of reinforced concrete gradient beams, with a maximum improvement of approximately 2.5 times. Compared with gradient beams reinforced with single long fibers, the peak impact force of HSFRC gradient beams increases by about 16%, and different steel fiber ratio plays a significant role in regulating impact resistance. Within the corrosion range of 3% to 5%, the equivalent impact bearing capacity of gradient beams is negatively correlated with the reinforcement corrosion rate.

Geopolymers have attracted increasing attention as sustainable binders, but their long-term durability in chloride-rich environments remains a critical concern. To elucidate the mechanistic role of calcined layered double hydroxides (CLDHs) in regulating the mechanical properties and chloride diffusion behavior of geopolymers, geopolymer pastes containing different CLDH contents were prepared. The compressive strength and chloride diffusion coefficient were determined, and the underlying mechanism was analyzed from the perspectives of geopolymerization degree, gel structure development, and pore structure evolution. The results indicate that the incorporation of CLDHs can promote geopolymerization, which may be associated with a nano-seeding effect, increasing the amount and degree of polymerization of the gel phases, refining the pore structure, and reducing pore connectivity. As a result, the compressive strength increases from 38.1 MPa to 49.2 MPa, while the chloride diffusion coefficient decreases by approximately 31.7% when the CLDH content reaches 6 wt.%. However, when the CLDH content exceeds this level, particle agglomeration limits effective gel growth, leading to microstructural deterioration and a weakened regulating effect.