In this study, the potential usage of wastewater bottle strips produced from polyethylene terephthalate (PET) as a reinforcing material for strength properties of cement stabilized clay was investigated. For this purpose; unconfined compression strength tests were conducted to determine the parameters affecting the strength properties of cement stabilized-reinforced clay. Four different ratios of cement (0, 3, 6, and 9%) were used for clay stabilization and waste bottle strips obtained by cutting from waste pet bottles were used for reinforcement. Considering that the waste bottle strips behave similar to the fiber material; cement stabilized-reinforced clay samples were prepared with the ratios of 0, 0.5, 1.0, 1.5, and 2.0%, which are generally used as reinforcement ratios for soil. The specimens were stored in the curing room for 1, 7, 28, and 90 days until testing. Test results were evaluated according to cement content, water bottle strip ratio and curing time parameters. The experimental results showed that the optimum water bottle strip ratio for maximum strength gain ranged from 1 to 1.5%. It was also observed that the plastic strips and cement used for soil improvement also changed the strength-deformation behavior of the kaolin clay. Besides, the augmentation in cement inclusion level and curing period increased the strength of kaolin clay. (C) 2021 Karabuk University. Publishing services by Elsevier B.V.