粉煤灰-矿渣基地聚物混凝土力学性能与微观结构

Mechanical property and microstructure of geopolymer concrete based on fly ash and slag

为考察不同配合比对地聚物混凝土性能的影响,开展了粉煤灰与矿渣比例、水玻璃模数以及水玻璃掺量(质量分数)对其宏观力学性能影响的实验研究,并从微观层次扫描电子显微镜(SEM)、能量弥散X射线分析(EDS)、X射线衍射(XRD)、傅里叶红外光谱(FT-IR)以及压汞实验(MIP)对微观结构进行研究。结果表明:养护龄期的增加,使聚合反应进行的程度提高,SEM微观形貌中观察到的凝胶量与种类逐渐增多,宏观上表现出更高的强度值;水玻璃模数的降低引起反应体系中硅铝比降低以及Na;的增加,促进了凝胶的生成,使其表现出较高的力学性能;粉煤灰与矿渣比例的减小,即在矿渣为反应体系中引入钙的含量增多,促进了凝胶的生成;当水玻璃掺量由20%增加到25%时,硅铝比由1.31增大到3.37,试样的微观结构致密性与宏观强度均表现提升;当水玻璃掺量过量时,硅铝比由3.37降低到2.00,导致凝胶结构不易形成,表现出强度的下降。降低水玻璃模数与提高矿渣比例均可促进聚合反应的进行,有助于地聚物混凝土力学性能与微观结构致密性的提升。

To analyze the impact of mix proportions on the performance of geopolymer concrete(GC), the effects of the ratio of fly ash(FA) to granulated blast furnace slag(GGBS), the sodium silicate modulus, and the content(mass fraction) of sodium silicate on the mechanical properties of geopolymer concrete were studied. Further, the microstructure of geopolymer concrete was investigated by means of scanning electron microscope(SEM), energy dispersive spectroscopy(EDS), X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FT-IR), and mercury intrusion porosimetry(MIP) tests. Results show that with the increase in curing age, the degree of polymerization was higher, the amount and types of gel observed in SEM images increased, and the macroscopic strength of geopolymer concrete was higher. The decrease in the modulus of sodium silicate resulted in the decrease in Si/Al ratio and increase in Na;, which promoted the formation of gel and made the geopolymer concrete exhibit higher mechanical properties. A decrement in the ratio of fly ash to slag, i.e. the increase in the amount of Ca in the system, promoted the generation of gel. When the content of sodium silicate increased from 20% to 25%, Si/Al ratio increased from 1.31 to 3.37, and the microstructure density and macroscopic strength of geopolymer concrete samples were improved. However, when the content of sodium silicate was excessive, Si/Al ratio decreased from 3.37 to 2.00, and the formation of gel was difficult, showing a lower strength of the geopolymer concrete samples. Reducing the modulus of sodium silicate and increasing the proportion of slag can both promote the polymerization, which is helpful to the improvement of the mechanical properties and the compactness of the microstructure of geopolymer concrete.