粉煤灰基矿物聚合材料的抗压强度和微观结构

以粉煤灰为硅铝原料,钠水玻璃为激发剂,在80℃下干燥养护6 h制备了矿物聚合材料。研究了钠水玻璃固相组成对试件抗压强度的影响,并通过X射线衍射、扫描电镜、27Al和29Si魔角自旋核磁共振方法分析了最优试件的物相组成、微观形貌和微观结构。结果表明,模数为1.5、Na2O掺量为10%(质量分数)的钠水玻璃激发粉煤灰制得的试件抗压强度约为18 MPa;SEM分析表明凝胶由纳米级颗粒组成,颗粒之间相互连接形成致密的空间网络;XRD和MAS-NMR分析表明矿物聚合材料具有一定的无定形状态,漫射峰对应的衍射角在25°～35°范围内,Al主要以四配位的AlQ4(4Si)结构单元存在,Si主要以Q4(2Al)和Q4(3Al)结构单元存在。

The compressive strength and microstructure of a fly ash-based geopolymer

A geopolymer has been prepared using fly ash as the silicon-aluminium precursor and sodium water glass as the activator after dry curing at 80 ℃ for 6 h.The influence of varying the solid phase composition of the sodium water glass activator on the compressive strength of the resulting material were studied.The compressive strength of the sample was about 18 MPa when fly ash was activated by sodium water glass with a SiO2∶Na2O weight ratio of 1.5 and Na2O dosage of 10%.The phase composition,morphology and microstructure of the optimal sample were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),and 27Al and 29Si magic-angle spinning nuclear magnetic resonance(MAS-NMR) spectroscopy.SEM analysis showed that the gel consists of a compact network structure linked by particles on a nanoscale.Both XRD and MAS-NMR showed that the geopolymer is amorphous.The XRD pattern showed a diffuse peak in the 2θ range 25°-35°,whilst the NMR spectra showed Al exists as AlQ4(4Si) tetracoordinate building blocks,while Si exists as Q4(2Al) and Q4(3Al) building blocks.