Evaluating the Strength and Durability Properties of Geopolymer-Stabilized Soft Soil for Deep Mixing Applications

Soft soil poses serious challenges and is unsuitable for engineering projects because of its insufficient bearing capacity, low shear strength, and high compressibility. Deep soil mixing (DSM) is one of the most popular methods of enhancing soft soil qualities, such as increased bearing capacity and reduced settling, which are critical for building any structure. The environmental effects of creating binders such as cement and lime make it crucial to identify alternative materials for geotechnical applications. This study employed fly ash (class C) --based geopolymer to investigate its effectiveness as an environmentally friendly substitute for cement for DSM applications. The experimental program included unconfined compressive strength, flexure strength, and durability tests. The parameters in the study are binder content (10, 15, and 20%) and activator/binder ratio (0.4, 0.6). Results revealed that UCS and flexural strength, GP-treated soil were in the range of 0.9–5.3 and 0.8–1.5 MPa, respectively (depending on the ratio of fly ash and activator). These strengths were even higher than those of cement-stabilized soil. The geopolymer-treated specimens exhibited excellent endurance over the wetting-drying cycle, with a modest weight loss of less than 4.5%. A binder dosage of more than 10% and an AC ratio of 0.6 were recommended to meet DSM application guidelines. The current study concludes that employing a fly ash-geopolymer binder to stabilize soft soil is an effective alternative to cement in DSM applications.