This study analyzes the behavior of clay soil reinforced with polyethylene terephthalate (PET) crushed from recycled bottles through experiments. A high-plasticity clay soil sample from the Peruvian jungle (Pucallpa, Ucayali) was used. Physical characterization tests were conducted, including the Atterberg limits, specific gravity, and the classification based on ASTM D2487 classification of the clay. Furthermore, tests were conducted to evaluate the mechanical properties of the soil, including Modified Proctor Compaction and California Bearing Ratio tests, to establish behavior patterns that can explain the influence of crushed PET on penetration and expansion parameters. In addition, for a better understanding of the materials used, Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD) were used for chemical characterization, involving determining the crystal structure of the minerals in the clay using infrared FTIR and electromagnetic XRD radiation. This characterization is critical because clay is a complex mixture of compounds, and the crystallinity of these minerals can significantly influence the behavior of clay. Finally, for research advancement, mixtures with crushed PET contents of 1.5% and 3.5% in relation to the dry weight of the soil were compared with the Standard Sample of natural clay.