**4. Conclusions**

The purpose of this study was to determine the effect of varying the percentage of nylon66 fiber in fly ash geopolymer concrete on strength performance. Furthermore, chemical, physical, and mechanical testing were performed for evaluating fiber properties, raw material characteristics, and geopolymers. Based on the analysis and experimental data results, the following conclusion can be drawn:


particles with beads to provide interlocking strength and contribute to good strength. More than 0.50% fiber insertion disrupts the CASH bonding in the geopolymer matrix and reduces its compressive strength.


**Author Contributions:** M.H.Y.—conceptualization, writing, original draft preparation; M.A.F. methodology, writing, original draft preparation; M.M.A.B.A.—formal analysis, project administration, methodology; M.S.I.I.—methodology, data curation; R.A.R.—data curation, formal analysis; D.D.B.N.—writing, review and editing, funding acquisition; D.P.B.N.—writing, review and editing, funding acquisition; O.B.—investigation, methodology; K.-S.N.—validation, investigation. All authors have read and agreed to the published version of the manuscript.

**Funding:** Ministry of Science, Technology and Innovation, Malaysia through MOSTI-Ted01 Grant TDF05211386. This work was also supported by Gheorghe Asachi Technical University of Ia¸si— TUIASI- Romania, Scientific Research Funds, FCSU-2022.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** The authors gratefully acknowledge the support of the Ministry of Science, Technology and Innovation, Malaysia through MOSTI-Ted01 Grant TDF05211386.This study was supported by the Center of Excellence Geopolymer and Green Technology (CEGeoGTech), Universiti Malaysia Perlis (UniMAP). This paper was also supported by "Gheorghe Asachi" Technical University from Ia¸si (TUIASI), through the project "Performance and excellence in postdoctoral research 2022".

**Conflicts of Interest:** The authors declare no conflict of interest.
