Synergistic effects of graphene oxide and fly ash on long-term durability and strength properties of concrete

This study investigates the long-term durability and strength performance of concrete incorporating Graphene Oxide (GO), Fly Ash (FA), and their combined use (GO-FA), focusing on compressive strength, chloride ion permeability, creep, and drying shrinkage. Over a 12-month period, four different concrete mixes were evaluated: Control Concrete Mix, GO Concrete, FA Concrete, and a combination mix of GO-FA Concrete. For the mixes incorporating GO and FA individually or in combination, the dosages were kept constant, with GO added at 0.12 % by weight of cement (bwoc) and FA at 30 % replacement. The GO-FA concrete exhibited the most significant improvements across all measured parameters. At 365 days, the mix showed an 18 % increase in compressive strength and an 80 % reduction in chloride permeability compared to the control mix. Additionally, creep and drying shrinkage were reduced by 16 % and 10 %, respectively. Microstructural analysis using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) confirmed a denser and more refined matrix in GO and GO-FA concretes. X-ray diffraction (XRD) analysis further revealed intensified calcium silicate hydrate (C-S-H) and progressive consumption of calcium hydroxide (CH) in GO-FA concrete. It confirmed the synergistic effect of the nucleation ability of GO and the pozzolanic reactivity of FA in enhancing concrete performance. Correlation analysis showed a strong negative relationship between compressive strength and RCPT values (r = -0.99) and a strong positive correlation between creep and drying shrinkage (r = 0.99), highlighting the combined influence of microstructure on durability and deformation. The findings confirm that the synergistic use of GO and FA enhances both short- and long-term performance, offering a sustainable solution for improving the durability of concrete in critical infrastructure applications. • Graphene Oxide-Fly Ash (GO-FA) concrete improved long-term compressive strength. • Chloride permeability of GO-FA concrete was significantly reduced over time. • GO-FA concrete mix showed a dense and balanced microstructure. • GO refined pore structure and enhanced C-S-H formation. • Time-dependent deformation properties of creep and drying shrinkage were improved in GO-FA concrete.