基于氮气吸附法的钙基地聚合物孔隙结构分形特征

Fractal Characteristics of Pore Structure of Calcium-based Geopolymer Based on Nitrogen Adsorption

在氮气吸附实验的基础上,对钙基地聚合物孔隙结构进行了分形特征研究,采用FHH模型和热力学模型分别计算了分形维数并比较了两种模型计算的结果,讨论了分形维数与孔隙结构参数、氢氧化钠掺量及宏观力学性能之间的关系。研究表明:钙基地聚合物的孔隙结构呈现明显的多重分形特征,FHH模型更适合表征钙基地聚合物的孔隙分形特征,根据FHH模型计算的分形维数在2~3之间;分形维数越大,孔比表面积和总孔体积越大,平均孔径越小,孔隙结构越复杂,钙基地聚合物的抗压强度越大;分形维数与氢氧化钠掺量无明显关系;孔隙结构的复杂程度是影响钙基地聚合物力学性能的重要因素。

The study on the fractal characteristics of the pore structure of calcium-based geopolymer were carried out base on the nitrogen adsorption experiment. The fractal dimensions were calculated by FHH and thermodynamic models, and the calculation results of the two models are compared in detail. Moreover, the relationship between the fractal dimensions and the pore structure parameters, the sodium hydroxide content and the macro-mechanical properties were discussed. It could be found in the results that the calcium-based geopolymer exhibit a pore structure of obvious multi-fractal features. FHH model was found to be more capable for the characterizing the fractal features of the pore structure of calcium- based geopolymer. The fractal dimensions calculated by FHH model ranged from 2 to 3. A larger fractal dimensions resulted in a larger pore specific surface area, a lager total pore volume, a shorter average aperture and a more complex pore structure, which contribute to improve the compression strength of calcium-based geopolymer. There is no obvious correlation between the fractal dimensions and doping amount of sodium hydroxide. In conclusion, the complexity of the pore structure has proven to be the main influence factor on the mechanical properties of calcium-base geopolymer.