Na_(2)SO_(4)/Na_(2)SiO_(3)复掺激发富镁镍渣-粉煤灰基地质聚合物的微观结构及性能研究

Microstructure and properties of magnesium rich nickel slag-fly ash based geopolymer excited by Na_(2)SO_(4)/Na_(2)SiO_(3)

通过扫描电镜、X射线衍射仪、傅里叶变换红外光谱仪和压力试验机,探究Na_(2)SO_(4)/Na_(2)SiO_(3)复掺激发剂对富镁镍渣-粉煤灰基地质聚合物强度、微观形貌及网络结构的影响。结果表明,利用正交实验法确定的最优试验方案,即粉煤灰掺量为30%、Na_(2)SO_(4)掺量为5%、水灰比为0.34制备的富镁镍渣-粉煤灰基地质聚合物试件养护28 d龄期的抗压强度可达27.5 MPa,与Na_(2)SiO_(3)激发制得的试件相比,其抗压强度提高了24.4%。在初期地质聚合反应中,Na_(2)SO_(4)的掺入延缓胶凝速率,随着养护龄期的延长,Na_(2)SO_(4)与体系中CaO反应消耗Ca^(2+),生成NaOH增加反应环境的碱度,使得活性SiO_(2)和Al_(2)O_(3)大量溶出,水化反应进程有所加快,起到协同激发的效果。SO_(4)^(2-)的不对称伸缩振动,导致体系出现“移峰”现象,系统中[SO_(4)]基团取代[SiO_(4)]基团,加速活性氧化铝的溶解,生成大量针状和板条状钙矾石(AFt),并促进钠镁铝硅酸盐凝胶(N-M-A-S)的形成。

In this paper,the effects of Na_(2)SO_(4)/Na_(2)SiO_(3) mixed activator on the strength,microstructure and network structure of magnesium rich nickel slag fly ash based geopolymer were investigated by scanning electron microscope,X-ray diffraction,Fourier transform infrared spectrometer and pressure testing machine.The results showed that the compressive strength of magnesium rich nickel slag fly ash based geopolymer specimen may reach 27.5 MPa after 28 days curing,which was 24.4%higher than that excited by Na_(2)SiO_(3).In the initial stage of geological polymerization,the addition of Na_(2)SO_(4) delayed the gelation rate.With the extension of curing time,the reaction of Na_(2)SO_(4) and Cao in the system consumes Ca^(2+),generates NaOH,increased the alkalinity of the reaction environment,was conducive to the dissolution of active SiO_(2) and Al_(2)O_(3),speeded up the hydration process,and played a synergistic excitation effect.The asymmetric stretching vibration of SO_(4)^(2-) resulted in the phenomenon of"shifting peak"in the system.In the system,[SO_(4)]group replaced[SiO_(4)]group,accelerating the dissolution of active alumina,generating a large number of needle shaped and plate-like ettringite(AFt),and promoting the formation of sodium magnesium aluminate silicate gel(N-M-A-S).