## 3 Results and Discussion
### Setting Time  
According to Figures 3 and 4, the results in Figures 5 and 6 can be determined using the interpolation method. Based on Figures 5 and 6, we can discuss the effects of FA and FGCBA on the initial and final setting times of concrete across various water-binder (W/B) ratios.  
The data indicate that at a W/B ratio of 0.4, the initial setting times for concrete with no replacement (FA or FGCBA) were relatively quick at 233.88 min. However, as the replacement level of FA increased to 40%, the initial setting time significantly rose to 419.82 min, and the final setting time extended to 679.97 min, suggesting a delay in the setting process due to the inclusion of FA. Interestingly, at 60% FA replacement, the initial setting time decreased to 363.39 min, while the final setting time peaked at 707.55 min, which may be indicative of the varying reactivity of FA at different replacement levels. In comparison, FGCBA replacements exhibited a decrease in initial setting time at 20%, followed by an increase at 40% and a decrease at 60%, with final setting times following a generally increasing trend.  
At a W/B ratio of 0.45, for FA, the initial setting times increased with the replacement level, with the longest duration recorded at 867.66 min for 60% replacement, which also corresponded to the highest final setting time at 790.16 min. For FGCBA, the initial setting time showed a dramatic increase at 40% replacement, reaching 665.12 min, with the final setting time at a striking 954.48 min. This suggests that the FGCBA may have a significant impact on retarding the setting process, particularly at higher replacement percentages. Interestingly, when the substitution rate of FGCBA was increased to 60%, both the initial and final setting times were shorter than those at 40% substitution rate, which may be related to the pores of FGCBA, which absorbed the excess water and resulted in a faster setting rate.  
Figure 4: _Cont._  
Figure 3: Influence of various FA replacement ratios on elapsed time and impedance resistance profiles at W/B ratios of (**a**) 0.4, (**b**) 0.45, and (**c**) 0.5.  
Figure 4: Influence of various FGCBA replacement ratios on elapsed time and impedance resistance profiles at W/B ratios of **(a)** 0.4, **(b)** 0.45, and **(c)** 0.5.  
Figure 5: Effect of different FA replacement ratios on setting time at W/B ratios of **(a)** 0.4; **(b)** 0.45; **(c)** 0.5.  
The patterns were similar when the W/B ratio was raised to 0.5, with FA replacements resulting in an increase in both initial and final setting times, but the increments were not as pronounced as those observed with FGCBA replacements. The final setting times for FGCBA at 40% and 60% replacements were notably high, at 714.10 min and 833.13 min, respectively, which could reflect a substantial retardation effect at these higher replacement rates.  
The data from this study reveal that both FA and FGCBA have discernible impacts on the setting times of concrete, with the effects becoming more pronounced as the W/B ratio increases. The inclusion of these materials, especially at higher replacement levels, tends to delay the setting process, which could be beneficial in applications in which extended workability is required. However, the substantial increases in setting times, particularly with FGCBA at higher W/B ratios, may necessitate adjustments in construction scheduling or the use of set accelerating admixtures to offset delays for practical applications.