为推进水库淤积物高值化利用,以三峡库区淤积物(SD)为核心原料,联合矿渣粉(GGBFS)与粉煤灰(FA)构建三元地质聚合物体系。通过21组配比试验,结合抗压强度测试、TCLP浸出试验、XRD、SEM-EDS、FTIR等表征方法,系统研究材料性能、固化机制、材料环境安全性。结果表明:当GGBFS掺量为20%时,淤积物占比80%的试样1 d抗压强度达70 MPa以上,XRD分析显示其绿泥石等黏土矿物大幅减少,C-A-S-H与C-S-H凝胶形成交错结构,归因于高活性的GGBFS溶出的Ca²⁺生成纤维状C-S-H凝胶与C(N)-A-S-H凝胶,消耗并降低了[SiO₄]^4-与[AlO₄]^5-浓度,促进了淤积物中硅铝质溶出;SEM证实FA的加入促进了体系生成沸石类硅铝酸盐矿物填充孔隙,提升了地聚体系28 d强度的稳定。研究表明,三元协同体系可同时实现淤积物大掺量(≥80%)资源化与材料性能优化,为疏浚固废制备高强地质聚合物提供理论和技术依据。

[Objective] Severe reservoir sedimentation reduces storage capacity and increases global desilting costs. Traditional disposal of dredged sediments (SD), such as landfilling, occupy land resources and pose ecological risks. This study aims to prepare high-strength geopolymers for high-value utilization of solid wastes. [Methods] Sediment from the Zhongxian section of the Three Gorges Reservoir (D₅₀≈67 μm) as the primary raw material. A ternary system is constructed by incorporating ground granulated blast furnace slag (GGBFS) and Class C Grade II fly ash (FA) to overcome alkali activation constraints, including high SiO₂/Al₂O₃ molar ratio of the sediments and the low reactivity of clay minerals. Specimens were cured under standard conditions for unconfined compressive strength (UCS) measurement. XRD, SEM-EDS, and FTIR characterized the mineral composition, microstructure, and surface functional groups of the ternary geopolymers. Additionally, the leaching concentrations of heavy metals (Cr, As, Cd, Co) from the ternary geopolymers were analyzed using the TCLP method with ICP-MS. [Results] In the SD-GGBFS-FA ternary system, the 28-day UCS ranged 51.9-82.9 MPa. The 1-day UCS increased with GGBFS content, indicated diminishing marginal efficiency of GGBFS reinforcement. For GGBFS and SD fixed at 80% and FA at 20%, increasing GGBFS from 0% to 80% produced 1-day UCS increments of 45.8,26.9,22.9,6.4 MPa, respectively, indicating higher alkali activation efficiency when the GGBFS content was below 40%. XRD patterns revealed a typical amorphous characteristic peak in this specimen in the 28°-30° range. SEM of the B2F8S0 specimen revealed the formation of a continuous and dense C-A-S-H gel, indicating that the co-alkali-activated product of GGBFS and SD was C-A-S-H gel, providing primary mechanical support for the early strength development of the material. FA, rich in components such as hematite and mullite, were hardly susceptible to alkali erosion at early ages. Increasing FA content improved stability of strength at later stages (28 d). At FA content of 40% or more, the UCS from 7 d to 28 d remained stable or even increased slightly, contrasting sharply with the significant strength attenuation of the GGBFS-SD system. XRD patterns showed that for B2S0F8 specimen (20% GGBFS + 80% FA) cured for 28 d, the crystalline peak of limestone (CaO) in FA disappeared, and characteristic diffraction peaks of zeolite-type C-A-S-H minerals emerged. FTIR revealed that, after 28 d of curing, the intensities of Si-O-Si stretching and Si-O bending vibration peaks in the B2S0F8 specimen remained stable, indicating greater geopolymer stability in this system than that in the B2S8F0 system. SEM confirmed that the tacharanite generated in the B2S0F8 system filled the pores, improving the compactness of the matrix and maintaining the long-term strength development. TCLP leaching tests showed that the leaching concentrations of Cd and Co from geopolymers were significantly lower than those from raw materials, indicating that Cd and Co could be stabilized by the geopolymer system. However, Cr and As mainly existed as anionic species, and the leaching concentrations of Cr and As from some samples increased after geopolymerization. [Conclusion] High-calcium GGBFS promotes the dissolution of low-activity aluminosilicate components in reservoir sediment clay minerals and forms dense C-A-S-H structures that enhance structural stability. In high-calcium environments, FA undergoes alkali-activated secondary reactions to generate tacharanite, which fills geopolymer gel pores and maintains long-term strength stability of the GGBFS-FA system. B2S6F2 achieves 72.4 MPa at 28 d, and its heavy metal leaching meets Class Ⅰ criteria. The ternary GGBFS-SD-FA system enables the preparation of environmentally safe, high-strength geopolymers, providing a reference for high-value sediment utilization.