The marine clay poses significant challenges in construction due to its high compressibility, low shear strength, and sensitivity to moisture. Stabilizing this problematic soil is critical for ensuring the durability and safety of civil infrastructure. This study investigates the potential of using recycled concrete powder (RCP), sourced from various demolition and construction sites, as an eco-friendly stabilizing agent for marine clay. The focus is on analyzing the influence of the silica-alumina (Si/Al) ratio in RCP on the binding potential during stabilization. RCP, rich in calcium silicates and aluminates, facilitates pozzolanic reactions when mixed with the high alumina content in marine clay. A series of laboratory unconfined compressive strength (UCS) tests was conducted to evaluate the effectiveness of RCP in improving the strength characteristics of marine clays. Energy-dispersive X-ray (EDAX) was employed to determine the Si/Al ratio of the recycled powders, and the investigation focused on the influence of compositional characteristics (Silica-alumina ratio) on the strength gain of RCP-treated marine clay. Scanning electron microscopy (SEM) analyses were used to study the cementitious compound formation in the treated soil. The optimal Si/Al ratio range promotes the formation of stable calcium-silicate-hydrate (C-S-H) and calcium-aluminate-hydrate (C-A-H) compounds, leading to better long-term stability. This study establishes the use of RCP in the stabilization of marine clay, thus promoting sustainable reuse of waste material.