Influence of adding waste polyethylene terephthalate plastic strips on uniaxial compressive and tensile strength of cohesive soil

Unconfined compressive strength and tensile strength are important geotechnical characteristics which are used for performance prediction and mix design in civil engineering projects. In recent years, the use of waste materials as reinforcement elements such as glass, rubber and plastic waste increased significantly. Nowadays, the use of polyethylene terephthalate (PET) has grown substantially for drink bottles which is one of the most important environmental hazards. In the current study, the effect of adding PET strips as reinforcement elements to a clayey soil has been studied by unconfined compressive strength and tensile strength tests. The compressive and tensile strengths of reinforced specimens with different PET contents (0%, 0.4%, 0.6%, 0.8% and 1% by the soil weight), lengths (12 mm to 21 mm) and widths (3 mm and 6 mm) have been investigated. It was found that addition of the PET strips to the clay resulted in an increase in both the compressive and tensile strengths. The optimum PET content was dependent on the both width and length of the PET strips. The maximum UCS was 321 kPa which observed in the specimen containing 0.8 % PET strips with 3 mm width and 18 mm length. The maximum tensile strength was 33 kPa which observed in the specimen containing 0.6 % of PET strips with 6 mm width and 15 mm length. The reinforced specimens containing I-shape PET elements exhibited a higher UCS value than that of the reinforced specimens with PET strips in most cases which is may be due to increase of friction between the soil particles and the PET elements.