Utilization of Depolymerized Recycled Polyethylene Terephthalate in Improving Poorly Graded Soil

Abstract

This study introduced recycled plastic waste as a soil stabilizer and encouraged using it as an alternative material in the improvement of poorly graded soil. The water bottles’ plastic waste was depolymerized and recycled to produce a powder material then used this material as a soil stabilizer. Different percentages (0.0, 0.5, 1.0, 1.5, 2.0%) of the depolymerized recycled polyethylene terephthalate (DRPET) (by dry weight of soil) have been chosen to evaluate its effects on the properties and behavior of poorly graded sandy soil. These effects studied through a series of laboratory tests including scanning electron microscopy. Also, the applicability of DRPET in inundation conditions has been studied using confined compression tests. It was found that untreated and treated poorly graded soil show the same shape of compaction curves, and DRPET filled the pore spaces and affected the compaction characteristics of the soil. The soil treated with 1.5 and 2.0% DRPET exhibited brittle behavior, and the addition of DRPET increased the angle of internal friction and reduced the maximum vertical contractive displacement of the soil. DRPET coated the surface of particles and increased the resistance between soil particles and, therefore, increased the time lag during compression. Finally, under confined compression, poorly graded soil treated with DRPET exhibited small changes in void ratio and slightly influenced by inundation in water.