## 3 Results and Discussion
### Drying Shrinkage  
The comprehensive data presented in Figures 9 and 10 provide a detailed evaluation of the drying shrinkage behavior in concrete mixes modified with FA and FGCBA at different aging periods. In the analysis of concrete with a W/B ratio of 0.4, it is evident that the inclusion of FA and FGCBA significantly affects the shrinkage characteristics. The shrinkage strain tends to increase with the age of the concrete, which is typical behavior resulting from the progressive loss of moisture over time. At 20% replacement with FA, the strain starts at \(-\)32.433 \(\times\) 10\({}^{-6}\) at day 1 and increases to \(-\)713.045 \(\times\) 10\({}^{-6}\) at day 91, indicating a consistent expansion of the drying shrinkage with time. When the replacement level is increased to 60%, a lower initial value of strain is recorded at \(-\)11.258 \(\times\) 10\({}^{-6}\), but it eventually reaches \(-\)1059.861 \(\times\) 10\({}^{-6}\), demonstrating a substantial increase in shrinkage which might be attributed to the higher volume of the porous FA particles contributing to the overall shrinkage of the concrete. The mixes with FGCBA replacements at the same W/B ratio show a trend of comparatively lower initial shrinkage strain than the FA mixes but experience a significant increase over time. For instance, it starts at \(-\)32.181 \(\times\) 10\({}^{-6}\) and escalates to \(-\)1391.693 \(\times\) 10\({}^{-6}\) on day 91 for 20% replacement with FGCBA, the highest among all mixes. This suggests that FGCBA might contribute to an increased propensity for drying shrinkage, potentially due to its physical and chemical properties. At a W/B ratio of 0.45, the shrinkage strain follows a similar pattern, with the FA replacement mixes demonstrating more pronounced long-term shrinkage compared to the control mix. For example, the 20% FA replacement demonstrates an initial strain of \(-\)75.757 \(\times\) 10\({}^{-6}\) which rises to \(-\)955.161 \(\times\) 10\({}^{-6}\) by day 91. Interestingly, at this ratio, the strain values for the 60% FA replacement reveal a somewhat lower final shrinkage of \(-\)1084.783 \(\times\) 10\({}^{-6}\) compared to the 20% replacement, suggesting a nonlinear relationship between FA content and drying shrinkage. With FGCBA, for 20% replacement at a W/B ratio of 0.45, there is an initial shrinkage strain of \(-8.046\times 10^{-6}\) which escalates to \(-1066.815\times 10^{-6}\) by day 91. It is noticeable that the shrinkage strain tends to be lower in FGCBA mixes than FA mixes at early ages but they converge or exceed as time progresses, indicating a complex interaction between the binder materials and the concrete matrix in terms of moisture movement and internal stresses. Regarding the mixes with a W/B ratio of 0.5, the control mix starts with an initial strain of \(-33.275\times 10^{-6}\) and reaches \(-842.288\times 10^{-6}\) by day 91. The 20% FA replacement mix begins at \(-19.331\times 10^{-6}\), showing a lower initial shrinkage but a final strain of \(-720.078\times 10^{-6}\), which is slightly below that of the control. This implies that at higher W/B ratios, the presence of FA could mitigate shrinkage to some degree. In contrast, the 60% FA replacement exhibits a higher rate of shrinkage over time, with the strain reaching \(-1038.084\times 10^{-6}\). For concrete containing FGCBA, the 20% replacement mix at a W/B ratio of 0.5 starts with a strain of \(-27.407\times 10^{-6}\), increasing to \(-1041.909\times 10^{-6}\) by day 91. The 60% replacement mix shows a notable increase in shrinkage strain over time, starting at \(-75.049\times 10^{-6}\) and culminating at \(-1058.602\times 10^{-6}\). Figure 9: Drying shrinkage of various proportions with age fort different amounts of FA replacing cement at W/B ratios of (a) 0.4; (b) 0.45; (c) 0.5. In summary, the data indicate that both FA and FGCBA contribute to the drying shrinkage of concrete, with the extent of their impact varying according to the W/B ratio and the percentage of replacement.