Evaluation of Metakaolin-Based Geopolymer as a Stabilizing Agent for Expansive Soil
The prevailing method currently used in treating and stabilizing expansive soil is chemical stabilization. The two materials that are widely used in this regard are lime and cement. They have proven over the years to be very effective in improving the geotechnical properties of soils. Nevertheless, they have high sustainability index, long term durability problem and high susceptibility to forming an expansive mineral -ettringite- in a sulfate rich soil, which necessitate their replacement with an alternative material that is more sustainable and less susceptible to ettringite formation. A potential material that stands the chance of replacing these conventional stabilizers is geopolymer, a solid and stable aluminosilicate material formed by alkali hydroxide or alkali silicate activation of metakaolin or fly-ash. Metakaolin-based geopolymer is, therefore, being evaluated by this research as an alternative stabilizing agent for expansive soils. In so doing, a metakaolin-based geopolymer was produced and utilized to treat an expansive soil obtained from Abuja, Nigeria. Subsequently, the geopolymer treated soil was tested for basic geotechnical and engineering properties, and the results were compared with the results obtained from testing of the control soil. The geopolymer was found very effective in enhancing the geotechnical properties of the control soil. Dramatic increase was observed in the unconfined compressive strength, CBR and maximum dry density, while drastic reduction was observed in the optimum moisture content, plasticity index, swell and shrinkage potentials of the control soil upon the addition of 15% geopolymer content. In order to evaluate geopolymer as an alternative to lime in soil treatment and stabilization, the soil was treated with lime and tested for geotechnical properties, and the results obtained were compared to those of geopolymer. Generally, the results revealed that geopolymer is an adequate substitute to lime for soil treatment and stabilization. It is therefore hoped that future research will appreciate the findings of this work in the execution of pavement design as a more sustainable alternative to conventional soil stabilizers.