During the past few years, in addition to traditional stabilizers, chemical and mineral substances have been produced and used for soil modification. New developments of such materials make it necessary to evaluate their effectiveness in any new project. The current study compares the effectiveness of lime and a polymer additive on the properties of clayey subgrade soil in a warm region. To assess the impact of stabilization, various physical and chemical microstructural tests on both treated and non-treated samples were carried out. In addition to these tests, CBR and unconfined compressive strength tests were performed on all samples. According to the results, it is concluded that lime can be utilized as the main stabilizer for the subgrade of the project with an optimum dosage rate of 2%. However, there are some concerns when working with lime, such as the swelling potential and ettringite formation in clayey soil-treated mixtures. Based on the results from swelling tests and SEM observation, the formation of ettringite seems unlikely in the process of lime stabilization in the soil matrix for this project. To assess the efficiency of lime stabilization, the pavement thickness was designed, and cost analysis was performed for both cases of treated and non-treated samples based on Australian Standards, including the empirical method (Main Roads WA Engineering Road Note No. 9) and the mechanistic method (CIRCLY). Results reveal that the construction savings from reducing the overall pavement thickness due to sustainable subgrade stabilization using different methods vary significantly between 15% and 30% compared to non-stabilized soil.