Strength Enhancement of Flexible Pavement Subgrades Using GGBS-Based Industrial Waste Stabilizers and Polypropylene Fibers

Black cotton soils are highly expansive and present major challenges in construction, especially for pavements. Stabilizing these soils using Ground Granulated Blast Furnace Slag (GGBS) and polypropylene fibers, both by-products of industrial processes, offers a sustainable solution. This research investigates the effects of GGBS and polypropylene fibers on critical soil properties, including Atterberg limits, maximum dry density (MDD), optimum moisture content (OMC), unconfined compressive strength (UCS), and free swell. By varying GGBS content from 0–30% and polypropylene fibers from 0–1%, the study identifies the optimal mix for stabilization. Results show that adding GGBS and polypropylene fibers significantly improves soil strength and reduces swell potential, enhancing its suitability for pavement applications.