Improvement of poorly graded sandy soil by using copper mine tailing dam sediments-based geopolymer and silica fume

Abstract

Production and utilization of new material with acceptable mechanical properties and the least environmental costs have always been pursued. The presented research was conducted to contribute to achieving this goal. Geopolymers are new binders that are likely to outweigh Portland cement due to their excellent strength and low greenhouse gas emissions. In this research, sandy soil was stabilized using a geopolymer based on copper mine tailing dam sediments (CMTDS) with different contents (10%, 15%, 20%) in different concentrations of potassium hydroxide (1 M, 4 M, 7 M, 10 M). A partial amount of CMTDS was replaced with silica fume (5%, 10%, 15%) to improve the used geopolymer. The specimens were characterized by compression strength tests, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR). Moreover, the best mixture conditions and the most influential parameter on the enhancement of compressive strength were determined by applying the Taguchi method and analysis of variance (ANOVA). At the end, the TCLP test was conducted to investigate environmental concerns regarding the used materials. The results indicated that a geopolymer based on CMTDS could be utilized to improve soil's compressive strength efficiently without damaging the environment. Inclusion of silica fume in the mixtures considerably improved the strength and microstructural density of specimens. Finally, statistical analysis illustrated that potassium hydroxide concentration was the most influential parameter for the compressive strength of specimens.