Experimental, Numerical, and Analytical Model of the Meso‐Mechanical Behavior of Linear Low‐Density Polyethylene Plastic and Sand Composite

ABSTRACT

Reusing plastic waste in construction materials offers a sustainable way to reduce environmental pollution; however, the low stiffness of recycled plastics limits their structural use. This study investigates the compressive behavior and elastic modulus of waste linear low‐density polyethylene (LLDPE) composites reinforced with sand at high volume fractions, focusing on construction applications that require deformation control. Composite specimens containing sand volume fractions of 0.34, 0.52, and 0.62 were fabricated and tested under uniaxial compression. A three‐dimensional mesoscale finite element model based on representative volume elements (RVEs) was developed to predict the effective elastic modulus and evaluate mesoscale deformation and load‐transfer mechanisms between the LLDPE matrix and sand particles. Experimentally, increasing the sand volume fraction from 0.34 to 0.62 increased the elastic modulus from 216.9 to 1683.3 N/mm ² , demonstrating substantial stiffness enhancement, although ductility and toughness decreased with increasing sand content. Numerical predictions showed excellent agreement with experimental results, achieving a coefficient of determination ( R ² ) of 0.99 and an average absolute error (AAE) of 1.11% across the investigated compositions. Mesoscale strain analysis further showed that increasing sand content reduced deformation localization within the LLDPE matrix, indicating enhanced load sharing and matrix constraint by the rigid sand particles. In addition, we proposed a modified analytical model to improve elastic modulus prediction at high filler contents, where classical analytical models show significant deviation. The proposed analytical model achieved an average AAE of 4.25% and provided substantially improved predictions compared with the classical models examined. The study's novelty lies in integrating experimental testing, validated three‐dimensional mesoscale modeling, and a modified analytical formulation for high‐volume waste LLDPE–sand composites containing up to 62% sand by volume. This combined experimental, numerical, and analytical framework provides a reliable approach to the design and development of sustainable waste‐plastic–mineral composites for selected nonstructural construction applications.