基于核磁共振技术的硅灰纤维浮石混凝土分形特征与强度关系分析

Relationship between Fractal Characteristics and Strength of Silica Fume Fiber Reinforced Pumice Concrete Based on NMR Technology

为探究硅灰与玻璃纤维对浮石混凝土的协同效应,用硅灰等质量取代水泥制备玻璃纤维浮石混凝土(GFRPC)并对其进行宏观力学试验。借助核磁共振技术(NMR)对GFRPC孔隙结构进行测试,并结合分形理论定量描述孔隙结构复杂程度,探讨孔隙特征参数、分形维数与抗压强度之间的关系。结果表明:硅灰与玻璃纤维的协同效应能有效提高GFRPC力学性能,与抗压强度相比,劈裂抗拉强度与韧性性能提高更为显著;GFRPC核磁共振T2谱呈“主次峰”结构,其孔隙结构具有明显多重分形特征,不同孔径范围孔隙分形维数及特征存在显著差异;添加硅灰能有效改善水泥基体与玻璃纤维、浮石骨料间界面过渡区的结构组成,增强其界面黏结性能。综合考虑孔隙特征参数和分形维数两方面因素对GFRPC抗压强度的影响,在此基础上建立的强度-孔隙结构模型拟合精度较高,模型预测值与试验值的平均相对误差为1.047%。

In order to explore the synergistic effect of silica fume and glass fibers on pumice concrete,glass fiber reinforced pumice concrete(GFRPC)was prepared by replacing cement with silica fume,and the macroscopic mechanical test was carried out.The pore structure of GFRPC was tested by means of nuclear magnetic resonance(NMR)technique,and the complexity of pore structure was quantitatively described by fractal theory.The relationship between pore characteristic parameters,fractal dimension and compressive strength was discussed.The results show that the synergistic effect of silica fume and glass fibers can effectively improve the mechanical properties of GFRPC.Compared with the compressive strength,the splitting tensile strength and toughness are improved more significantly.The T2 spectrum in GFRPC nuclear magnetic resonance shows a“primary and secondary peak”structure,and the pore structure has obvious multifractal characteristics.There are significant differences in pore fractal dimension and characteristics among different pore sizes.The addition of silica fume can effectively improve the interface transition zone between cement matrix,glass fiber and pumice aggregate,and enhance the interfacial bonding property.Considering the influence of pore characteristic parameters and fractal dimension on GFRPC compressive strength,a strength-pore structure model established on this basis has high fitting accuracy.The average relative error between the predicted value of the model and the experimental value is 1.047%.