Sustainable Soil Stabilisation Using Plastic Waste

The practice of soil stabilisation is popular to increase the bearing capacity and strength of weak subgrade soils. Traditional stabilisers like lime and cement enhance soil performance, but their sole use can result in higher costs and environmental impacts. This research paper examines the synergy effect of using recycled polyethene terephthalate (PET) bottle fibres with lime and cement in subgrade stabilisation. Two systems were tested: lime-PET (LP) and cement-PET (CP). The content of total stabiliser (binder and PET) was adjusted between 2% and 10% by dry mass of soil with a ratio of 1:1 binder to fibre. The soil samples were collected in Pokhara, Nepal, and subjected to compaction tests, including California Bearing Ratio (CBR) at 95% maximum dry density (MDD), and unconfined compressive strength (UCS) according to IS standards. The highest CBR at 95% MDD was 12.03% for LP6 and 13.20% for CP8, compared to 4.11% for untreated soil, corresponding to increases of approximately 192.7% and 211.16%, respectively. UCS improved by 143.07% for LP6 and 162.98% for CP8 relative to untreated soil. The results indicate that a regulated use of PET fibres that are chemically stabilised improves the performance of subgrades and can be used to reuse plastic waste in pavements.