Experimental Evaluation of Waste-LDPE Strips for Improving Pavement Subgrade Soil

Abstract

This study evaluates randomly distributed Low-Density Polyethylene (LDPE) strips as reinforcement for three pavement-subgrade soils. Cleaned milk-pouch plastic was cut to a 5 mm width, and the planned experimental domain covered 1%–4% LDPE by dry soil mass and aspect Ratios (AR) of 2, 4, 6, and 8. The complete numerical record available for verification comprises the dosage series at AR 6 together with strength checks at the selected condition; complete numerical results for AR 2, 4, and 8 are not reported. Standard compaction, four-day soaked CBR, and UCS responses were evaluated, while the reported triaxial parameters were treated as supplementary because the underlying principal-stress records were unavailable for independent recalculation. Soaked CBR increased from 4.25%, 5.82%, and 3.40% in untreated Soils A, B, and C to 8.46%, 12.74%, and 6.28% at 3% LDPE with 5 mm × 30 mm strips (AR 6), corresponding to gains of 99.1%, 118.9%, and 84.7%. MDD losses at this condition were 1.23%, 0.81%, and 1.90%, and UCS increased by 121.8–184.6%. CBR declined at 4% LDPE in all three soils. Accordingly, 3% LDPE at AR 6 is identified as the best common verified condition within the complete AR 6 dataset, not as a globally proven geometry optimum. Replicate-level observations were unavailable; therefore, the reported percentage changes are descriptive and are not presented as statistically significant differences. Further replicated testing across AR 2, 4, and 8, together with durability and field validation, is required before general specification.