Abstract

The migration of contaminants from a site in the soil represents a real threat to the environment and to human health because contaminants might leach to groundwater and humans could be affected directly and indirectly. Therefore, the objective of this research was to evaluate the vulnerability of silica based chemical grout barriers to protect leaching of contaminants to groundwater. Thirty five experiments were done using calcium chloride (SC), formamide (SF) and combined reagents (SFC) with sodium silicate, along with three different types of soil. Sand, silty sand and sandy silt soils were contaminated with nickel (1000 ppm) or phenanthrene (600 ppm) or mixture of both contaminants. A resistance-based methodology was developed to find out the internal grout changes of grouted specimens. Grouted specimens were submerged in water which was simulated low-mineralized and high-mineralized groundwater. The results show that soil resistivity went up in all specimens. The highest coefficient of stability was found to be 6% in mixed (nickel-phenanthrene) contaminated soil grouted with SF. There was no phenanthrene release from grouted contaminated soil. The nickel release was as low as 4~5 ppm. Furthermore, a complex of sodium formate was found in water based on FT-IR analysis. Lastly, the values of pH and redOx confirmed the stabilization process. This research showed that to reduce contamination with heavy metal, silica formamide (SF) grout should be used. Contamination with phenanthrene was best treated with formamide (SF grout) and a combined (SFC grout) reagent. It was also found that a combination of both reagents made setting faster and created more stable conditions. A model was developed for prediction of contaminant stability. The results of this research can be applied to stabilize any kind of soil with particle size from 1.0 mm to 0.053 mm, contaminated with PAHs and heavy metals.