## 5 Conclusions  
This study comprehensively evaluated the stabilization potential of Glass Fiber Chopped Strands (GFCSs), calcium carbonate (CaCO\({}_{3}\)) and nano-calcium carbonate (nano-CaCO\({}_{3}\)) as additives for improving the geotechnical behavior of clay soils. The experimental data provide valuable insights into the individual and combined effects of these materials on bearing capacity enhancement and reduction in consolidation settlements.  
As a result of this study, it was determined that the additives CaCO\({}_{3}\), nano-CaCO\({}_{3}\) and GFCSs used to improve the geotechnical properties of clay soils have significant effects. The application of CaCO\({}_{3}\) at a 5% ratio promoted pozzolanic reactions and cation exchange, thereby increasing the shear strength of the soil and reducing settlements. This improvement was achieved through the interaction of Ca\({}^{2+}\) ions with clay particles, which enhanced flocculation and reduced the void ratio. The effectiveness achieved with a low dosage supports the economic and environmental feasibility of this method.  
Nano-CaCO\({}_{3}\), even at a much lower ratio of 0.75%, produced superior results compared with traditional CaCO\({}_{3}\) due to its high surface area and reactivity. The nano-sized particles penetrated small pores, resulting in early age bonding, denser microstructure formation and lower compressibility. This shows that the material offers significant advantages in terms of cost effectiveness and sustainability due to its high performance at low dosages.  
The GFCS fibers provided three-dimensional tensile resistance to the soil, significantly improving tensile strength, ductility and crack resistance. The best results were obtained with a 2.0% fiber content, but when combined with nano-CaCO\({}_{3}\), a 1.5% GFCS ratio was sufficient. This demonstrates a synergistic effect between chemical and mechanical stabilization, achieving a higher performance with reduced additive amounts.  
In terms of curing time, it was observed that chemical reactions and fiber-soil bonding were largely completed within the first 14 days, with improvements stabilizing afterward. Therefore, a minimum curing period of 14 days is recommended for field applications.  
When GFCSs and nano-CaCO\({}_{3}\) were used together, the consolidation settlements were reduced by up to 6.8 times. While nano-CaCO\({}_{3}\) enhanced particle bonding and soil density, GFCSs limited deformations, reducing the time-dependent settlements.  
Overall, the combined use of chemical and fiber additives significantly improved soil strength, ductility and long-term performance. The success achieved with low additive ratios reduces both the costs and environmental impacts. In particular, the high efficiency of nano-CaCO\({}_{3}\) presents a promising path for the widespread use of nanomaterials in geotechnical engineering.  
This research underscores the technical feasibility and practical advantages of employing combined nano-scale chemical additives with fibrous reinforcement for sustainable and effective clay soil stabilization. The findings offer valuable guidance for geotechnical engineers seeking to optimize soil improvement techniques for enhanced infrastructure durability and safety.  
Conceptualization, B.B. and B.M.; methodology, B.B.; validation, B.B. and B.M.; formal analysis, B.B.; investigation, B.B., B.M. and A.U.; resources, B.B.; data curation, B.B. and B.M.; writing--original draft preparation, B.B. and B.M.; writing--review and editing, B.B. and B.M.; visualization, A.U.; supervision, B.B.; funding acquisition, B.B., B.M. and A.U. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.  
The authors declare no conflicts of interest.