Mechanical and electrical properties of spent catalyst-based cement mixes admixed with graphene oxide

This study investigates the combined effect of graphene oxide (GO) and spent fluid catalytic cracking catalyst (ECAT) on the hydration behavior, workability, mechanical performance, electrical conductivity, and microstructure of cement mortars. GO was incorporated at 1–3% and ECAT at 10% as a partial cement replacement. Isothermal calorimetry revealed that GO accelerated early hydration, increasing the cumulative heat release by nearly 20% compared to the control, while ECAT delayed hydration due to dilution. Flow tests showed that GO progressively reduced workability, particularly in ECAT-containing mixtures. Mechanical testing demonstrated that 1% GO enhanced compressive strength by about 6% and elastic modulus by nearly 15% at 28 days, while 10% ECAT alone reduced these properties; however, the combination of ECAT with low dosage in GO restored and even surpassed the control, achieving up to 12% higher modulus. In addition to mechanical improvements, significant enhancements in electrical properties were observed. The incorporation of GO increased electrical conductivity at 3 wt% GO, corresponding to nearly a 47% increase. Although ECAT alone slightly reduced conductivity, the combined ECAT–GO system exhibited the highest electrical performance, reaching approximately 2.8 mS/m for the mixture containing 10 wt% ECAT and 1 wt% GO, which represents an increase of about 65% compared to the control. These results demonstrate that the synergistic use of GO and ECAT not only improves mechanical behavior but also enables the development of electrically conductive and self-sensing cementitious composites. These findings highlight the novelty and potential of combining GO with catalytic residues to develop sustainable and multifunctional cementitious composites with enhanced mechanical and electrical performance.