## 4 Conclusions  
This work provides new insight on the ability of nanoclay particles to improve the interfacial bond of coated fiber with a cementitious matrix. The fiber-matrix interaction was investigated by means of single fiber pull-out tests. The morphological and chemical investigations of the coatings were compared with the results obtained from the load displacement curves in order to obtain a deeper insight in the factors that influence the fiber pull-out behavior. From the results obtained, the following conclusions can be drawn:  
* The dispersion quality of nanoclay particles in the coating can be affected by further ingredients, as it was observed in this work for the cross linking agent. * The single fiber tensile strength is mainly depending on the silane treatment; no positive effect was arising from the nanoclay containing polymer coatings. * The silane-treated fibers (PTMO) display higher IFSS but lower W\({}_{total}\). This indicates that the PTMO fibers have a high interfacial adhesion due to the chemical bonding with the matrix. However, the resulting force drop after reaching F\({}_{max}\) indicates only minor fiber-matrix interaction during further pull-out; hence, brittle failure occurs. Figure 10: Force-displacement curves of single fiber pull-out tests, with the different colors of the curves relative to the individual samples tested. * The application of a coating increases the friction between the fiber and the matrix resulting in higher pull-out work. * For both SB and CSB coatings, the addition of MMT particles produced an increase of the IFSS and the pull-out work. This can be attributed to a better interaction with the cementitious matrix and to the ability of nanoclay particles to work as nucleating species for the formation of hydration products. * The increase of the polymer roughness did not lead to an increase of the pull-out load. This suggests that the modification of the chemical characteristics have a major impact on the interaction with the cementitious matrix. * According to the results presented, the main benefit obtained from the dispersion of nanoclay particles in the coating consists in providing a better interaction based on chemical bonding in combination with improved mechanical interlocking. However, the potential, in terms of durability and mechanical performances, of engineering the fiber-matrix interface with a nanostructured coating are much greater. Further studies are certainly needed to better explore the applications of this technology. Particularly, future works should focus on the improvement of the coating in order to obtain a better dispersion of the nanoclay particles in the polymer. For this purpose, different protocols for the preparation of the coating can be considered. In addition, the possibility to use other polymers and nanoclay particles can be examined. Moreover, the optimal amount of nanoclay dispersed in the coating should be defined. Finally, the results obtained on a microscale should be confirmed by investigation conducted on a macroscale. Conceptualization, F.B. and C.S. ; methodology, F.B. and C.S. ; investigation, F.B. ; resources, F.B. ; data curation, F.B., C.S., and T.U. ; writing--original draft preparation, F.B. and C.S. ; writing--review and editing, C.S., T.U., and J.D. ; supervision, C.S. and J.D. ; project administration, C.S. All authors have read and agreed to the published version of the manuscript. This research is partly funded by the German Research Foundation (Deutsche Forschungsgemeinschaft-DFG) within the framework of SFB/TRR280, Project-ID 417002380. Not applicable. The authors greatly acknowledge the funding by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) in the framework of the Collaborative Research Centre SFB-TRR280 \"Design Strategies for Material-Minimized Carbon Reinforced Concrete Structures--Principles of a New Approach to Construction\" project ID 417002380. The authors are grateful to [PERSON] for providing the nanoclay particles.