Abstract: The study investigates the factors influencing the unconfined compressive strength (UCS) of geopolymer-stabilized construction spoil. Using fly ash as the primary raw material and NaOH as the alkaline activator, geopolymer binders were prepared to solidify spoil generated from foundation-pit excavation. The effects of alkali-activator dosage, curing temperature, and curing duration on the UCS of the stabilized soil were analyzed. The results show that the UCS of the stabilized soil increases rapidly at first and then more slowly—and may even slightly decline—as the activator dosage, curing time, and curing temperature increase. The greatest strength improvement occurs when the activator dosage is 19%, the curing time reaches 16 hours, and the curing temperature is maintained at 60℃. Hydration reactions between fly ash and the alkaline activator generate silicate and aluminate hydration products, which enhance the strength and stability of the stabilized soil through precipitation, adsorption, and pore-filling mechanisms.

Key words: Fly-Ash-Based Geopolymer, Alkaline Activator Agent, Curing Age, Curing Temperature, Solidified Soil ,