Stabilization of Clay Subgrade using Geopolymer Synthesized from Slag, Fly-Ash, Diatomite and Rice Husk Ash

This paper aims to investigate and compare the properties of highly plastic clay soil stabilized by geopolymers synthesized from various industrial residues and rice husk ash. To this end, steel slag, fly-ash and diatomite were used as the base material, and NaOH solutions of 8.68 M and Na2SiO3 solutions extracted from rice husk ash were used as an alkaline activator for stabilization. Stabilization was performed using 10, 20 and 30 percent of base materials by dry weight of soil. Samples were compacted at optimum moisture content and were cured for 7, 28 and 90 days. The results of the experiments show that the application of geopolymer as a stabilizer improve the compressive and tensile strength, increase Young's modulus and reduce the failure strain of the stabilized clay soil. The highest increase in the unconfined compressive strength (UCS) was related to stabilized clay with geopolymer synthesized using 30% of steel slag, its UCS was 25.2 times higher than the untreated clay soil. Also, the samples stabilized with geopolymer synthesized using 30% of fly-ash and 30% of diatomite showed the UCS of 4.05 and 12.72 times more than the untreated clay soil, respectively. The results of this study also showed that the stabilization of clay using geopolymer significantly increases the indirect tensile strength (ITS) of the samples, so that the samples stabilized with geopolymers based on the 30% of steel slag, 30% of fly-ash and 30% of diatomite, had an ITS of  23.14, 7.58 and 12.5 times more than untreated clay soil, respectively.