Formulation of Geopolymer Stabilized Soil with Different Sodium Silicate to Sodium Hydroxide Ratios Based on Physical and Mechanical Properties

Abstract

This study investigates the formulation of geopolymer stabilized soil using varying sodium silicate (Na₂SiO₃) to sodium hydroxide (NaOH) ratios, focusing on the physical and mechanical properties of lateritic soil. In this work, fly ash-based geopolymer binders were prepared at contents of 3%, 5% and 7% of the total mix mass and activated with an alkaline activator comprising sodium silicate solution and a 10 M NaOH solution at Na₂SiO₃-to-NaOH mass ratios of 2.0, 2.5 and 3.0. The physical properties of the soil were characterized through Atterberg limit, particle density, particle size distribution and compaction tests in accordance with BS 1377:1990, while the mechanical performance was evaluated using the unconfined compressive strength (UCS) test after 0, 7 and 28 days of curing. The soil was classified as sandy silt of intermediate plasticity, with a maximum dry density of 1.735 Mg/m³ at an optimum moisture content of 18.39%. The results showed that a 5% geopolymer binder with an Na₂SiO₃/NaOH ratio of 2.5 achieved the peak UCS of 0.2173 MPa after 28 days of curing, showing comparable strength to the 7% binder content (0.2143 MPa) while providing a more efficient mix design. The findings highlight the importance of optimizing both the binder content and the alkaline activator ratio in geopolymer stabilization, offering a sustainable alternative to conventional methods for enhancing soil strength in geotechnical engineering applications.