Abstract <p>This paper deals with an environmentally friendly approach to the stabilization of soft marine clays using granulated blast furnace slag, a major industrial byproduct produced by iron and steel industrial plants in India. This can reduce the hazardous waste disposal of these slags, which are stockpiled, and also reduce the greenhouse gases generated during the production of conventional stabilizers such as cement and lime. The study evaluates the performance of slag-based geopolymers activated with alkali reagent as a potential stabilizer for soft marine clay deposits using physical and strength performance tests, compressibility tests, mineralogical and microstructural studies such as scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) and thermogravimetric analysis. The soft marine clayey soil was treated with slag-based geopolymers at dosages of 2%, 4% and 6%, cured for 7, 30, 90, 180, 365 and 730&#xa0;days, and then compared with the conventional stabilizers such as lime and slag. After 730&#xa0;days of curing, the strength test results revealed that the strength of slag-based geopolymer was 13 times greater than that of untreated marine clay deposits and more than twice that of both lime-stabilized and slag-stabilized soil. It also significantly improved the compressibility parameters compared to lime-treated soil, reducing the compression index by 30% and the coefficient of secondary compression by 86%, whereas lime-treated soil showed reductions of only 8% and 73%, respectively. These results indicate the potential of slag-based geopolymer stabilization as a viable alternative to the conventional lime stabilization of soft clays.</p> Graphical Abstract <p></p>