Geotechnical Evaluation of Clay Stabilized with Blast Furnace Slag and Fly Ash

Clayey soils, often characterized by their high plasticity, excessive compressibility, and low shear strength, pose considerable challenges for construction and infrastructure development due to their poor load-bearing capacity and susceptibility to volumetric changes. Effective stabilization of such soils is therefore crucial to improving their geotechnical behavior and ensure long-term structural performance. This study investigates the potential of utilizing industrial waste materials—namely, blast furnace slag (BFS) and fly ash (FA)—as alternative stabilizing agents to enhance the engineering properties of problematic clays. The research specifically examines the influence of a binary binder composed of BFS and FA mixed in a fixed ratio of 60:40. The binder was incorporated into the soil in varying dosages, ranging from 10 to 50% by dry weight, to comprehensively evaluate its impact on compaction characteristics and unconfined compressive strength (UCS). The results reveal a notable enhancement in soil performance, evidenced by increased maximum dry density and reduced optimum moisture content—indicative of improved compactability and densification. Furthermore, the stabilized soil exhibited substantial strength gains, with UCS values rising significantly in response to higher binder content and extended curing periods. Beyond technical performance, this stabilization strategy offers environmental benefits by valorizing industrial by-products that would otherwise contribute to waste accumulation. The combined use of BFS and FA thus not only improves soil behavior but also aligns with sustainable construction practices, supporting circular economy principles and reducing the environmental footprint of ground improvement techniques.