Combining High-Density Polyethylene (HDPE) Plastic Waste with Sand for Sustainable Construction in Plastic Brick Manufacturing

Plastic waste poses a significant environmental challenge due to its long decomposition time. A promising solution involves converting plastic waste into construction bricks, including applications for floating structures. This study explores the feasibility of utilizing high-density polyethylene mixed with sand to produce sustainable building bricks. A total of 9 test specimens and 3 control specimens, all made entirely from HDPE, were prepared. Three investigations were conducted. The first method combined HDPE with sand in ratios of 70%–100% HDPE and 0–30% sand. The highest compressive strength, 51.43 MPa, and shear strength (0.700 MPa) were achieved with more sand content. All rations met the lightweight criteria and showed minimal weight. The water absorption in HDPE blended with sand at varying ratios affects the moisture resistance. With 70% HDPE and 30% sand additive, HDPE-sand absorbed 1.3342% water. Next were 80% HDPE-20% sand 0.5775% and 90% HDPE-10% sand (0.4876%). absorbed the least water at 100% HDPE, 0.3982%. Ratios enhance water resistance, making them suitable for moisture-sensitive applications. The 100% HDPE control group has a density of 0.08814 in all combinations, ranging from 0.0932 with 10% sand, whereas the 80% HDPE-20% sand density increases to 0.0982. The maximum density is 70% HDPE-30% sand. Overall, HDPE mixed with sand improved strength and ensured material stability, making these blends viable for eco-friendly construction.