Discussion on “Potential improvement in the mechanical performance and thermal resistance of geopolymer with appropriate microplastic incorporation: A sustainable solution for recycling and reusing microplastics”

We read with great interest the paper by Xie et al. (2024) that describes the methodology for recycling and reusing microplastics, MPs, by utilizing it into the geopolymer, GP, matrix made from fly ash, FA, and ground granulated blast furnace slag, GGBFS. The GP was created by activating the FA and GGBFS (7:3 ratio) using 16 M NaOH. Herein the MPs of various sizes (viz. 50, 150, and 500 µm) and varying percentages (viz. 2.5, 5, 7.5, and 10) were encapsulated in the GP matrix and further, they were cured at 40 and 80 C for 24 h and later at ambient temperatures. Several experiments were performed to investigate the physical (viz. bulk density, fluidity, thermal resistance), mechanical (viz. compressive strength, flexural strength), mineralogical, and microstructural properties of synthesized GP. Furthermore, these samples were exposed to elevated temperatures viz. 200, 400, and 600 C to investigate the effect of MPs on the thermal resistance of GP matrix. Although, Xie et al. (2024) have presented some intriguing findings, however there are serious issues concerning the proposed ideology and subsequently, its justification, which the authors would like to highlight through this discussion.