In this study, the effects of blast furnace slag (BFS), an industrial waste product, on the strength of a clayey sand soil were investigated. For this purpose, the soil to be used first was subjected to various laboratory tests to determine the geotechnical properties of the soil. Then, test samples were prepared by adding BFS to the ground in varying proportions of 5% to 30% by weight. Optimum water contents and maximum dry unit weights were determined by applying standard proctor test to both pure and stabilized soil samples. Pure and stabilized soil samples prepared in this water mixture were subjected to unconfined pressure and California bearing ratio tests after completing their 1 and 7-day curing periods. As a result of the experiments, the most effective additive ratio was obtained from the 10% BFS added samples after 7 days of curing. It was found that the unconfined compressive strength and CBR values of the samples in this ratio increased by 1.18 and 1.81 times, respectively, compared to the pure soil. According to these results, it was observed that 10% BFS additive has a healing effect on the unconfined compressive strength and bearing capacity of clayey sand soils.