## 4 Conclusions  
The study confirms that the use of alternative binders such as CLW, GY, and GG can effectively improve the mechanical behavior of compacted clay soils. The results show that glass powder and limestone waste provided consistent improvements in strength and stiffness, especially at higher compaction densities. Recycled gypsum also contributed positively, though its effect was somewhat less pronounced in comparison.  
Xanthan gum (XG) significantly enhanced both strength and stiffness, especially when combined with polypropylene fibers (PPFs). Although the fixed percentage of PPF prevented its inclusion in the statistical analysis due to zero degrees of freedom, the experimental evidence suggests that its presence contributes to better energy absorption and ductile response. The mixtures containing XG-PPF achieved the highest performance values, supported by a denser internal structure observed in the microstructural analysis.  
The porosity/binder index (\(\eta/B_{iv}\)) proved to be a useful tool for predicting mechanical performance. The relationships established between this index and the values of q\({}_{\text{u}}\) and G\({}_{\text{o}}\) showed high reliability, with determination coefficients close to or above 0.90. However, it was not possible to integrate XG-based mixtures into a single predictive trend due to their gel-like behavior, which differs from that of mineral binders. This limitation required a separate model to represent the response of those systems adequately.  
The ANOVA supported the experimental trends, identifying cement content and compaction density as the most significant variables. While some interaction terms were not statistically relevant, the observed trends in strength and stiffness aligned with the model's predictions. The analysis helped reinforce the importance of combining experimental and statistical methods to guide the development of efficient and sustainable soil stabilization alternatives.  
Future research should explore the long-term durability and environmental performance of these alternative binders under field conditions, particularly in the presence of moisture fluctuations and aggressive chemical environments. Additionally, the optimization of XG-PPF ratios and the development of adaptable predictive models for biopolymer-based systems remain important challenges. Investigating the interaction of these binders with different soil types could also broaden their applicability in geotechnical engineering.  
**Author Contributions:** Conceptualization, J.d.J.A.B. and Y.E.N.d.I.R.; methodology, J.d.J.A.B.; software, J.d.J.A.B.; validation, Y.E.N.d.I.R. and R.T.O.; formal analysis, J.d.J.A.B.; investigation, J.d.J.A.B.; resources, Y.E.N.d.I.R. and R.T.O.; data curation, J.d.J.A.B.; writing--original draft preparation, J.d.J.A.B.; writing--review and editing, Y.E.N.d.I.R.; visualization, J.d.J.A.B. and R.T.O.; supervision, J.d.J.A.B.; project administration, Y.E.N.d.I.R.; funding acquisition, Y.E.N.d.I.R. All authors have read and agreed to the published version of the manuscript.  
**Funding:** The Fundacion Universitaria Los Libertadores (Bogota, Colombia) funded the APC.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data are contained within the article.  
**Acknowledgments:** The authors thank the Universidad de Cartagena. The authors thank [PERSON] for the writing and editing assistance.  
**Conflicts of Interest:** The authors declare no conflicts of interest.