Consolidation and microstructural behaviour of soil treated with palm oil fuel ash-based geopolymer

In recent times, geopolymer has gained attention as a soil stabilization binder due to its ability to improve soil’s engineering properties while remaining eco-friendly. This study seeks to investigate the stabilization of soft soil using palm oil fuel ash (POFA)-based geopolymers. The geopolymer was created by combining POFA with an alkaline activator solution composed of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). The mechanical and microstructural behaviour of two clayey soil types stabilized with four doses of POFA-based geopolymer (G10PA, G20PA, G30PA, G40PA) was studied by conducting one-dimensional consolidation, California Bearing Ratio (CBR), Field Emission Scanning Electron Microscopy (FESEM), and X-Ray Diffraction (XRD) tests. The optimum dosage found was G40PA in both soil samples. The CBR value of S1-G40PA was 1.7 times the S1 while S2-G40PA was nearly 1.5 times the S2. The void ratio of S1 was significantly reduced from 0.70 (untreated sample) to 0.56 (S2-G40PA), whereas for S2, it was decreased from 1.43 (untreated sample) to 0.43 (S2-G40PA). The microstructural analysis (FESEM) revealed that changes in material composition correlate to consolidation behaviour, with the geopolymer gel-binding effect enhancing the mechanical properties of stabilized soils.