纳米SiO2改性高炉矿渣-粉煤灰地质聚合物固化土力学性能OA

To address the issues of high energy consumption,significant carbon emissions,low early strength,and poor water stability in cement-stabilized soil,this study used ground granulated blast-furnace slag(GGBS)and fly ash as precursors,water glass as activator to prepare geopolymer,and added nano-SiO2 to solidify the soil.Through unconfined compressive strength tests and water stability tests,combined with microscopic analyses including scanning electron microscopy,energy-dispersive spectroscopy,and nitrogen adsorption,the effects of nano-SiO2 content and curing age on the mechanical properties of geopolymer-stabilized soil were investigated.The results indicate that the unconfined compressive strength of geopolymer-stabilized soil initially increases and then decreases with increasing nano-SiO2 content,with an optimal nano-SiO2 content of 0.6%(mass fraction).When the mass ratio of GGBS to fly ash is 5∶5,7∶3,and 9∶1,the unconfined compressive strength is 16.0%,22.4%and 26.5%,respectively,higher than that of the undoped nano-SiO2 specimen.The higher the content of GGBS is,the more significant the effect of nano-SiO2 on the unconfined compressive strength of geopolymer-solidified soil is.With the increase of curing age,the unconfined compressive strength of geopolymer-stabilized soil gradually increases,but the effect of nano-SiO2 on the unconfined compressive strength decreases.When the mass ratio of GGBS to fly ash is 7∶3,the strength growth rates at 7,14,and 28 d for specimens with nano-SiO2 are 22.4%,15.4%,and 6.0%,respectively,relative to those without nano-SiO2.The incorporation of nano-SiO2 improves the water stability and reduces the strength loss rate of the specimens.Microscopic analysis reveales that nano-SiO2 enhances the compressive strength and water stability of geopolymer-stabilized soil through chemical reactions,particle filling,and nucleation effects.Nitrogen adsorption test results show that with increasing nano-SiO2 content,the cumulative pore volume and the proportion of large pores in the specimens first decrease and then increase,which is consistent with the change of mechanical properties.