Micronized Biomass Silica as a Reactive Precursor in Geopolymer-Stabilized Marine Soil: Strength and Durability Assessment

Marine soils, distributed indefinitely around the world, because of their low strength characteristics, high compressibility, high plasticity, and sensitivity have created an imperative need for their stabilization. This study aims to improve marine soil using a novel geopolymer based on micronized biomass silica (MBS), a carbon-free green product produced at a lower cost than silica fume manufactured from rice husk ash. The effects of several parameters, including binder dosage, alkali-to-binder ratio (L/B), alkali activator ratio (NS/NH), and molarity of NaOH solution, were examined to choose the best mix proportions based on strength enhancement. The durability performance was assessed using the cyclic wetting and drying method. Furthermore, this study investigated the mechanisms underlying the reported strength augmentation in treated marine soil, as well as the microstructural and physiochemical interactions, using Field-emission Scanning Electron Microscopy (FESEM), Energy-Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD) analyses. The optimal dosage for geopolymerization in the marine soil studied was at a binder of 15%, alkali activator ratio of 2, alkali-to-binder ratio of 0.8, and NaOH of molarity 8M, which yielded the highest UCS value of 1,033 kPa at 28 days of curing, 16 times that of untreated soil. With a durability index value greater than 1, all evaluated samples endured 12 cycles of wetting and drying with little volume change and minimal surface damage. Finally, SEM, EDS, FTIR, and XRD results revealed that the cementing components in the geopolymer-stabilized clay were sodium aluminosilicate hydrate (N─A─S─H) and Zeolites, which increased the soil structure density through bonding and filling effects. A comparative life cycle assessment verified the system’s environmental advantage, demonstrating a 22% reduction in its carbon index over traditional cement-based stabilization. This investigation presents a promising approach that improves the geomechanical characteristics of marine soil through the application of waste materials.