Performance Comparison of Recycled HDPE, PET, and LDPE in Construction Materials: A Systematic Review

This systematic review examines the use of three common recycled plastics, which are: high-density polyethylene (HDPE), polyethylene terephthalate (PET), and low-density polyethylene (LDPE), for the manufacturing of bricks and blocks, focusing on their mechanical and physical properties. The study addresses two major industry challenges: managing increasing plastic waste and developing sustainable alternatives to conventional building materials. Following PRISMA 2020 guidelines, a comprehensive search was conducted across five academic databases for peer-reviewed studies published between 2014 and 2025. After careful screening and quality assessment, 26 studies were included in the analysis, covering plastic type, replacement ratios, mechanical and physical properties, and manufacturing methods. The common manufacturing methods used are melt and bind, dry mixing, binder addition, aggregate substitution and small percent incorporation. The results show that HDPE consistently provides the highest compressive strength, often exceeding 20 MPa at optimal replacement of around 7.5% and 75:25 for the melt and bind method. Polyethylene terephthalate showed moderate strength but excellent flexural performance, with optimal ratios from 15% to 30%. Low-density polyethylene produced highly variable results, with peak compressive strength of 24.83 MPa at only 0.5% replacement, and reduced strength at higher levels. For all plastic types, density decreased by about 5% to 15%, such as from 1.67 to 1.58 grams per cubic centimetre in bricks containing polyethylene terephthalate. Water absorption trends were varying, such as polyethylene terephthalate often lowering absorption by up to 20%, while higher low-density polyethylene contents tended to increase it.