Grouted gravel column (GGC) is an innovative foundation treatment technique that combines the higher bearing capacity of concrete piles and the drainage benefits of stone columns. A series of model tests were conducted to investigate the feasibility of using alkali-activated mortar (AAM) as grouting material for the construction of GGCs. The AAM was mixed by the sulfur iron ore tailing (SIOT), ground granulated blast furnace slag (GGBS), and metakaolin (MK) as a solid binder and the NaOH and Na₂SiO₃ mixture as alkaline activator. It is found that the SIOT-GGBS-MK AAM is an effective grouting material for the construction of GGCs. The surface grouting specimens have unconfined compressive strengths (UCSs) of 2.21–3.17 MPa and an elastic modulus of 119.07–233.91 MPa, which were lower than those of jet grouting specimens with UCSs ranging from 7.68 to 9.70 MPa and an elastic modulus of 370.71–503.67 MPa. The GGCs behave as rigid inclusions in the soil, with its failure occurring when the applied load exceeds the combined resistance of the soil along the column shaft and at the column tip, causing the entire column to penetrate downward. Very few GGCs with low strength formed by the surface grouting method fail through crushing on the column shaft.