Mechanical Properties of Concrete Blocks Incorporating Recycled Waste Plastic

Concrete production with waste plastics as a replacement for aggregates has continued to lead discussions on the probable solutions to plastic waste threats. However, investigation on the direct application of concrete incorporating waste plastic for the production of walling units is yet to receive the desired considerations. This study aims to evaluate the effect of fine aggregate substitution with waste plastic aggregate on concrete blocks to determine appropriate material mixes that can satisfy the requirements for application as walling material. Samples of concrete blocks were prepared using natural sand, plastic waste, cement and water at a 1:4 binder-to-aggregate ratio with consistent workability. The composite materials were tested for compressive strength, flexural strength, splitting tensile strength, elastic modulus, water absorption and sorptivity. The study found that waste PA increases the compressive strength of plastic aggregate (PA) concrete blocks at 5% PA, reaching 23.92 N/mm² in 28 days. The splitting tensile strength of PA composites and the flexural strength of PA concrete blocks are increased by the replacement of natural sand with PET aggregate, attaining 1.5 and 11.81 N/mm², respectively. Beyond 5% PA content, the water absorption of PA concrete blocks increased, while the sorptivity decreased with an increase in the PA content. The study indicates that the use of 5% volume of PA in the production of concrete blocks can substantially enhance mechanical properties and water absorption. This production technique can help the construction industry safely use recycled waste PA in the production of masonry units with enhanced mechanical properties and improved resilience in wet environments.