为绿色低碳处置渣土并进行资源化利用,通过碱激发高炉矿渣(ground granulated blast-furnace slag,GGBS)作为绿色固化剂固化淤泥质工程渣土进行路基填料应用,探究不同固化剂掺量对固化土的综合性能影响规律,采用X射线衍射(X-ray diffraction,XRD)、扫描电镜(scanning electron microscopy,SEM)、核磁共振(nuclear magnetic resonance,NMR)对固化效果进行微观表征,用分形理论阐述微观孔隙特征揭示碱激发GGBS固化淤泥质渣土机理.结果表明:固化剂增加了固化土液塑限,降低了塑性指数,最优含水率随固化剂掺量增加呈现先减少后增大的趋势,最大干密度与之相反.掺入固化剂提高了渣土力学性能和水稳性,10%的掺量的固化渣土,强度、加州承载比(California bearing ratio,CBR)、水稳性以及渗透性分别为2.36 MPa、210.7%、81.3%和1.36×10-7 cm/s,各项指标均能满足路基填筑强度要求.微观机理表明,改良土的主要水化产物为(N,C)-A-S-H以及钙矾石Aft,固化体主要孔隙数量减少,10%的掺量的固化渣土,中孔隙减少了14.7%,孔隙分布分维数由1.23减小为1.06.通过碱激发GGBS固化淤泥质工程渣土,改善了渣土的稳定性,具有较好的应用前景.
Properties and Mechanism of Solidified Silty Sediment from Alkali-Activated Slag
For promoting a green,low-carbon way of disposition of architecture sediment and resource utilization,alkali-activated blast furnace slag(GGBS)as a green solidification agent was adopted to solidify mucky engineering waste soil for subgrade filling.The influence of different dosages of solidification agent on the comprehensive performance of solidified soil was explored.Furthermore,X-ray diffraction,scanning electron microscopy and nuclear magnetic resonance were carried out to characterize the properties of the so-lidification.Fractal theory was used to describe the micropore characteristics and a generalized model was established to reveal the mechanism of alkali-activated GGBS solidification of muddy muck.The results show that the liquid limit and plastic limit of the solidi-fied soil is increased and the plasticity index is reduced owing to the curing agent.The optimum moisture content decreased first and then increased with the increase of the content of the curing agent.The maximum dry density is the opposite compared with that of the optimum moisture content.The addition of curing agent can improve the mechanical properties and water stability of slag soil.The strength,CBR,water stability,and permeability of 10%solidified slag is 2.36 MPa,210.7%,81.3%,and 1.36×10-7 cm/s,re-spectively.All indicators can satisfy the engineering application requirement.The micro-mechanism showes that the main hydration products of the improved soil are(N,C)-A-S-H and ettringite Aft.The number of main pores in the solidified soil is reduced.For the slag with10% of calcium solidification agent,the middle pores are reduced by14.7%,and the fractal dimension of pore distribution is reduced from 1.23 to 1.06.The solidification of muddy engineering waste soil by alkali activated GGBS has improved the stability of the waste soil and has good application prospects.
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