复合降碱改性生态多孔混凝土抗硫酸盐侵蚀性能研究OA

In order to improve the service durability of ecological porous concrete(EPC)in a sulfate dry-wet cycling environment,a composite alkali-reduction system was established using diatomaceous earth(DE),oxalic acid(OA)and ferric sulfate(FS).EPC specimens with different alkalinity gradients were prepared,and the evolution of macroscopic property and the variation of microstructure under sulfate dry-wet cycles were systematically investigated.The macroscopic deterioration behavior of EPC was characterized by relative compressive strength and mass loss rate,while hydration products and microstructural features were analyzed by XRD,FTIR,and SEM.The results show that moderate alkali reduction significantly improves the sulfate erosion resistance of EPC.Among the specimens,the group with 1.2%(mass fraction)OA-FS composite system(pH=9.0 to 10.0)still maintains the highest relative compressive strength(72.59%)after 24 sulfate dry-wet cycles.Microstructural characterization shows that the DE-OA-FS composite system optimizes the pore structure and chemical stability of EPC by promoting the formation and structural stabilization of C-S-H gel,slowing the rapid consumption of Ca(OH)2,and inhibiting the concentrated precipitation of sulfate-attack products such as ettringite(AFt),thereby delaying the process of crack propagation and carbonation-induced deterioration.The findings provide a technical reference for durability optimization design and engineering applications of EPC in complex aggressive environments.