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

Abstract

In recent times, geopolymers have gained attention as a soil stabilisation binder due to their ability to improve the engineering properties of soil while remaining eco-friendly. This study seeks to investigate the stabilisation of soft soil using palm-oil-fuel-ash (POFA)-based geopolymers. A geopolymer was created by combining POFA with an alkaline activator solution composed of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). The mechanical and microstructural behaviours of two clayey soil types (samples S1 and S2) stabilised with four doses of the POFA-based geopolymer (G10PA, G20PA, G30PA and G40PA) were studied by conducting one-dimensional consolidation, California bearing ratio (CBR) tests, field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The optimum dosage found was G40PA for both soil samples. The CBR value of S1-G40PA was 1.7 times that of S1, while that of S2-G40PA was nearly 1.5 times that of 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 with the consolidation behaviour, with the geopolymer gel-binding effect enhancing the mechanical properties of stabilised soils.