Using Waste PET Shreds for Soil Stabilization: Efficiency and Durability Assessment

Abstract

Encountering weak fine-grained soil presents a significant challenge during highway construction. The conventional approach to address this challenge involves incorporating calcium-based stabilizers, particularly cement, for stabilization. However, despite its widespread use, the application of cement for soil stabilization has adverse environmental consequences. Accordingly, finding alternative methods to minimize cement usage has become a prominent area of research, from researchers worldwide. This study evaluates the effectiveness of utilizing discarded polyethylene terephthalate (PET) bottle shreds as soil reinforcement alongside lower cement contents. To this end, soil samples were mixed with varied contents of two grades of shredded PET. The ground PET pellets, which displayed diverse shapes, demonstrated properties resembling fibres. Compacted samples were subjected to CBR to determine optimum PET content. Strength, small-strain stiffness and durability of soils in original state, mixed with cement and PET were measured by a programme of CBR, wetting–drying cycles, and ultrasonic pulse experiments. Findings suggest a 28–91% increase in strength of soil upon its mixing with cement—PET shreds. Substituting cement with cement—PET shred led to a drop in accumulated loss of mass (ALM). In twelve cycles of wetting and drying, the small-strain stiffness initially decreased, but then stabilized at approximately the same value in the subsequent cycles. The porosity to binder ratio was adopted as an index for CBR, ALM and the maximum shear modulus. The latter was finally proposed as a measure for durability.