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石粉對赤泥基注漿材料的影響機制

Influence mechanism of limestone powder on red mud-based grouting material

  • 摘要: 為明確石粉摻合料對地聚物材料的作用機理,以赤泥基注漿材料為研究對象,系統研究了石粉摻量和粒徑分布對赤泥基注漿材料漿體性能、力學性能和微觀結構的作用規律,并結合X射線衍射儀(XRD)、壓汞儀(MIP)和掃描電鏡(SEM)等微觀測試手段分析其作用機理。研究表明,結石體力學強度隨石粉摻量的上升先增大后減小,當石粉的質量分數為5%時抗壓強度最高,3 d時可達5.65 MPa,抗壓強度提升幅度為18.94%,同時漿液泌水率上升幅度僅為9.85%,且28 d結石體孔隙率降低了18.35%,因此,5%為石粉在赤泥基注漿材料中的最佳質量分數。在石粉最佳質量分數條件下,隨著石粉平均粒徑減小,漿液凝結時間及泌水率均呈現下降的趨勢;當石粉平均粒徑達到8 μm時,石粉“填充效應”和“成核效應”作用尤為明顯,漿液黏度突升,且3 d和28 d試樣強度分別提升了11.86%和10%,故石粉平均粒徑越小,其對赤泥基注漿材料的提升作用越顯著,赤泥基注漿材料的最佳粉料質量配比為赤泥47.5%,礦粉47.5%,石粉5%;微觀分析證實,石粉在漿液水化歷程中以物理特性參與其中,為Na2O–SiO2–Al2O3–H2O凝膠(N–A–S–H), 水化硅鋁酸鈣凝膠(C–A–S–H)和水化硅酸鈣凝膠(C–S–H)等凝膠提供成核位點,供地聚物凝膠沉淀和生長,加速漿液水化。

     

    Abstract: Considering the unstable performance of geopolymeric materials due to the large fluctuation of the raw-material composition and the high alkalinity of the system, this study investigated the effect of limestone powder on red mud–based geopolymeric grouting materials; moreover, the influence mechanism was analyzed via X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM). Also, the study provided some reference to reduce the storage of red mud and realize the collaborative utilization of limestone powder and red mud–based grouting materials. The results show that the mechanical strength of specimens first increases and then decreases with the increase in the limestone powder content. The compressive strength of the specimen with 5% limestone content was the best: the 3-day compressive strength could reach 5.65 MPa, which was 18.94% higher than that of the specimen with 0% limestone powder content. Moreover, the slurry bleeding rate of the 5%-limestone specimen was only 9.85% higher than that of the 0%-limestone specimen, and the porosity of the former on day 28 was 18.35% lower than that of the latter. Therefore, 5% is the best content of limestone powder in red mud–based grouting material. When the mean particle size of limestone powder was 8 μm, the “filling effect” and “nucleation effect” of specimens were significant, and the slurry viscosity rose sharply; the compressive strengths of day-3 and day-28 samples increased by 11.86% and 10% than those of the corresponding bulk-limestone samples, respectively. Thus, the smaller the mean particle size of limestone powder, the more significant the improvement effect of red mud based grouting material. The optimum proportion of red mud–based grouting materials was 47.5% red mud, 47.5% blast furnace slag, and 5% limestone powder. The macro analysis confirms that limestone powder participates in the slurry hydration process, providing nucleation sites for N–A–S–H, C–A–S–H, and C–S–H gel, which can be used for geopolymer gel precipitation and growth and accelerate the slurry hydration.

     

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