Effects of CO2 and chloride ion interaction on the durability of one-part nickel slag geopolymer

To investigate the interaction between carbonation and chloride ions on the durability of single-phase nickel slag geopolymer mortar, three experimental conditions were designed: (A) chloride ion penetration followed by carbonation, (B) carbonation followed by chloride ion penetration, and (C) carbonation, chloride ion penetration, and wet-dry cycles. Macro-performance was assessed through compressive strength, pH values, and chloride ion concentration, while microstructural mechanisms were analyzed using XRD, TG-DTG, and SEM. Results showed that chloride crystallization delayed carbonation, while carbonation products enhanced resistance to chloride penetration. The synergy of carbonation and wet-dry cycles accelerated chloride transport, thickening the surface convection zone. XRD and TG-DTG analyses confirmed the formation of hydrotalcite-like phases due to the high MgO content in nickel slag. No Friedel’s salt was detected, suggesting chloride ions were captured mainly through physical adsorption of the amorphous gel phase.HighlightsCarbonation was delayed by chloride crystallization, while chloride resistance was enhanced by pre-carbonation.Chloride transport was accelerated by the synergy between carbonation and cyclic wet-dry exposure.Hydrotalcite-like phases were identified, while chloride was primarily through physical adsorption. Carbonation was delayed by chloride crystallization, while chloride resistance was enhanced by pre-carbonation. Chloride transport was accelerated by the synergy between carbonation and cyclic wet-dry exposure. Hydrotalcite-like phases were identified, while chloride was primarily through physical adsorption.为探究碳化与氯离子交互作用对单相镍渣基地质聚合物砂浆耐久性的影响，本研究设计了三种实验工况：(A) 先开展氯离子渗透再进行碳化，(B) 先进行碳化再开展氯离子渗透，(C) 同时实施碳化、氯离子渗透与干湿循环。宏观性能通过抗压强度、pH值及氯离子浓度进行表征，微观机理则采用X射线衍射（XRD）、热重-差热重分析（TG-DTG）与扫描电子显微镜（SEM）开展分析。研究结果表明，氯离子结晶会延缓碳化进程，而碳化产物可提升材料抗氯离子渗透性能；碳化与干湿循环的协同作用会加速氯离子传输，使表面对流区增厚。XRD与TG-DTG分析证实，由于镍渣中氧化镁含量较高，生成了类水滑石相；未检测到弗里德尔盐（Friedel’s salt），表明氯离子主要通过无定形凝胶相的物理吸附被捕获。研究亮点：氯离子结晶可延缓碳化，预碳化处理能够提升材料抗氯离子渗透性能；碳化与周期性干湿暴露的协同作用可加速氯离子传输；检测到类水滑石相，氯离子主要通过物理吸附作用被固定。氯离子结晶可延缓碳化，预碳化处理能够提升材料抗氯离子渗透性能；碳化与周期性干湿暴露的协同作用可加速氯离子传输；检测到类水滑石相，氯离子主要通过物理吸附作用被固定。