Silica fume stabilized loess: Mechanical properties, microstructural evolution and environmental analysis

The stabilization of loess is gaining increasing attention due to some of its physical properties which are highly prone to trigger some geological hazards. Common stabilizers (lime, cement and fly ash) release a significant proportion of greenhouse gases during their production, so it is becoming increasingly important to find an environmentally friendly or industrial waste material to stabilize loess. Silica fume is one such industrial waste material that can be used as a stabilizer in the stabilization of loess foundations. In this work, the unconfined compression strength of samples with different silica fume contents was measured, suggested that silica fume remarkably improved the strength for the samples. Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and energy-dispersive X-ray spectroscopy (EDXS) techniques were used to explore the microstructure and quantify the microstructural parameters through Image-Pro Plus (IPP) software to explain the variation in mechanical properties of samples with different silica fume content. The results indicated that the stabilization of the loess by silica fume consisted of both chemical and physical stabilization. Chemical stabilization was the reaction between silica fume and loess particles to produce C-S-H gels, while physical stabilization was the addition of silica fume which filled the pore volume and caused a variation in the shape and angle of the pores, thereby increasing the mechanical strength. The environmental impact of stabilizing 1 m3 of loess with a common stabilizer was studied by life cycle assessment (LCA) under similar unconfined compressed strength conditions, thus demonstrating the need to promote the use of silica fume in the loess foundation stabilization market.