Effective Use of Waste Plastic As Sand in Metakaolin/Brick-Powder Geopolymer Concrete

This study proposes recycling waste clay brick and waste polyethylene terephthalate (PET) bottles as substitution materials in geopolymer concrete. To accomplish this goal, the control mix of geopolymer concrete was prepared based on blended metakaolin and waste clay brick powder (CBP) at a 1:1 mixture by weight. To evaluate the use of shredded PET particles as fine aggregate, three mixtures were made by replacing sand with PET aggregate at volumetric percentages (10%, 15% and 20%). The specimens containing PET aggregate were tested and compared against the control mix (0% PET), with emphasis on the fresh and dry densities, mechanical performance, water absorption and microstructure characteristics. The results indicated the inclusion of PET aggregate to slightly reduce density and improve mechanical properties. When compared to the control mix, the compressive strength of the 20% PET replacement increased to 28.1 MPa after 28 days. Moreover, the concrete with 20% PET obtained the lowest water-absorption rate. The scanning electron microscopy images revealed that the inclusion of waste PET as sand had a significant effect on the microstructure of Mk-CBP geopolymer concrete. When compared to the control mix, the matrix containing 20% PET had a denser microstructure, as well as fewer holes and microcracks, in addition to the packing of paste at the interfacial transition zone.