Performance assessment of geopolymer stabilized aggregate pavement bases with incorporation of biomedical waste incinerated ash

This research investigates the potential of repurposing biomedical waste incinerated ash (BMWIA) as a precursor material in geopolymerization to stabilize crushed aggregates (CA) for asphalt pavement bases, aiming to enhance environmental sustainability and infrastructure resilience. The strength and stiffness of CA stabilized with BMWIA-based geopolymers were evaluated through unconfined compressive strength (UCS), indirect tensile strength (IDTS), and indirect resilient modulus (IT Mr) tests. Additionally, durability against wetting and drying cycles, leaching of heavy metals, and carbon footprints were assessed for the mixes optimized using a novel ranking process. Experimental results demonstrated that UCS and IDTS of BMWIA-based geopolymer-stabilized CA increased with higher CA/BMWIA (up to 80/20) and Na₂SiO₃ / NaOH (up to 50/50) ratios. This improvement is attributed to the formation of stable geopolymeric sodium aluminosilicate hydrate (N-A-S-H) across all curing periods. The optimal CA/BMWIA ratio of 80/20, activated at a Na₂SiO₃/NaOH ratio of 50/50, met the design requirements for high-volume roads (UCS > 5 MPa) specified by the Indian Road Congress (IRC):37-2018. Furthermore, selected mixes demonstrated mass loss after 12 wetting and drying cycles and heavy metals concentrations below the limits prescribed by IRC: 89 -2018 and the United States Environmental Protection Agency (US EPA) standard, respectively. Compared to cement-stabilized CA with similar UCS values, BMWIA-based geopolymer-stabilized CA exhibited lower carbon footprints. This research confirms the viability of BMWIA-based geopolymer-stabilized CA as an alternative material for stabilized pavement bases, offering a sustainable solution for managing biomedical waste while improving infrastructure resilience.