Sustainable composite blocks from plastic waste and rice husk ash: mechanical properties and microstructural characterization

Abstract The increasing accumulation of plastic waste and underutilization of agricultural by-products such as rice husk ash (RHA) highlight the need for sustainable material development. This study investigates the potential of combining Polypropylene (PP) plastic waste and rice husk ash to produce eco-friendly composite blocks. Three compositions were prepared: 80% PP: 20% RHA, 70% PP: 30% RHA, and 60% PP: 40% RHA. Mechanical characterization included compressive strength and wear resistance tests, while microstructural features were examined using Scanning Electron Microscopy (SEM). The results revealed that increasing the RHA content resulted in a reduction in compressive strength and an increase in wear. The 80% PP: 20% RHA composition achieved the highest compressive strength (21.06 MPa, Grade B) and the lowest specific wear (0.000194 mm 3 /kg·m). SEM analysis revealed greater porosity and weaker interparticle bonding at higher ash levels, which explained the decline in mechanical performance. Overall, the study demonstrates the feasibility of valorising plastic and agricultural waste into composite blocks with acceptable strength and wear resistance. The findings provide a pathway for developing sustainable construction materials that support both waste reduction and circular economy practices.