| Summary: | The effect of combined nano materials on mechanical properties of high-volume fly ash mortar (HVFAM) was carried out in this investigation. The characteristics of HVFAM mixes were first evaluated using slump flow tests. Then, the mechanical properties of HVFAM including the measurement of setting time and the development of early-age compressive strength were performed. Structural changes during hydration were analyzed using FTIR analysis. The study utilized fly ash (FA) as a 60% replacement for cement, with the addition of 0.01% carbon nanotubes (CNT) and graphene oxide (GO) with five different dosages ranging from 0.01% to 0.05%. Results of study showed that the incorporation of hybrid CNT and GO significantly affected the mechanical properties of HVFAM. Specifically, increased of CNT and GO contents lead to significant reduction in both workability and setting time of HVFAM, with a more pronounced reduction in final setting time compared to initial setting time. The development of early-age strength of HVFAM improved by 15.8% with the highest 28 day-strength increasing by approximately 23% at 0.01% CNT and 0.03% GO dosages. FTIR analysis confirmed that the improved earlyage strength was attributed to the accelerated hydration of cement caused by the seeding effect. The outcome of the study provides a suitable approach for the development of eco-friendly materials with improved mechanical properties that could be effectively used for HVFAM.
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