Thermo-mechanical degradation and multiscale performance of hybrid PPS-MWCNT reinforced lightweight geopolymer composites

This study examines the thermo-mechanical behavior of lightweight-engineered geopolymer composites (LEGC) reinforced with polyphenylene sulfide fibers (2.0%) and multi-walled carbon nanotubes (0.2%) by weight of binder. The composites were synthesized using mining waste-derived and industrial by-products, including fly ash, GGBS, cenospheres, silica-fume, and rice-husk ash, a pathway for valorizing mine tailings and smelter slags. The composites were exposed to elevated temperatures up to 800 °C. Physico-mechanical performance, evaluated and supported by ANOVA/Tukey’s HSD tests, show strength enhancement at 200 °C (22% compressive, 19% flexural) due to matrix densification. Progressive degradation occurred at higher temperatures. At 800 °C, significant reductions occurred due to geopolymer matrix decomposition and fiber melting. Microstructural analyses (SEM/XRD/FTIR/TGA-DTG) revealed increased porosity/microcracking, with PPS degradation-linked bubble growth (400 °C–600 °C). MWCNTs maintained crack-bridging at moderate temperatures, partially mitigating damage. This study underscores the temperature-dependent degradation mechanisms and the role of hybrid reinforcement in improving thermal resilience within circular contexts including mine’s waste valorization.