<p>The study of Periwinkle shell has continued to attract improved research around and within the people. These shells are produced worldwide on a daily basis, mainly from domestic sources, markets, restaurants, open fields, landfills, and eateries and can be harmful if disposed of indiscriminately. This study aimed to utilize processed periwinkle shell ash as a sustainable and innovative material to improve the characteristics of clay soil for stabilization purposes and to preserve pavement structure. The clay soil was collected as an undisturbed sample using an auger from Ntak Inyang in Uyo, Nigeria. The laboratory tests included the California bearing ratio test, Unconfined compressive strength test, durability test, sieve analysis and consistency limit test. Microstructural analyses such as Scanning Electron Microscope and X–Ray Diffraction were performed to identify functional groups and mineralogical changes present in the clay-PSSA admixtures. The results obtained at 5.5% stabilization showed improvements in the UCS from 392.77 kN/m² to 460.60 kN/m² and in the CBR from 32.07% to 61.60% and 21.00% to 46.81% for unsoaked and soaked samples respectively. The OMC increased from 15.36% to 17.02% and the MDD increased from 1.61 g/cm³ to 1.88 g/cm³ as the percentage of stabilizer increased. Based on the results, 5.5% stabilization was observed to yield optimum results for road work. Therefore, in order to protect the environment from the harmful effects of cement stabilization, there is an urgent need to replace conventional materials with locally available sustainable and economically viable alternatives. This substitution will help reduce the overreliance on cement usage worldwide. The novelty of this research lies in facilitating the hydration of CaCO₃ and Ca(OH)₂ compounds which leads to the formation of calcite minerals through carbonation reactions in stabilized clays during chemical processes.</p>