# Nuclear Magnetic Resonance in Tire Waste Mortars
## 4 Conclusions  
This study demonstrated the potential of low-field NMR as an effective, non-destructive method to analyze the microstructural evolution of mortars containing recycled rubber and various additives. The optimal composition identified--3.5% NHL and 5% rubber flakes--achieved a balanced performance in terms of water retention and stability. Quantitative analysis of T\({}_{2}\) relaxation time distributions enabled the differentiation between bound water, capillary water, and free water across pore sizes, supporting precise pore structure evaluation. These insights help guide the design of functional, eco-friendly mortars suitable for specialized applications like animal housing floors.  
During the analysis, it was found that the MV3F5% formulation, comprising 3.5% natural hydraulic lime and 5% rubber flakes, exhibited optimal performance in terms of water retention and internal structure stability over time. Even though NHL 3.5 lime exhibits a reduced degree of mechanical strength in comparison to NHL 5, it is distinguished by a more organized pore structure and a less aggressive pore evolution, factors which collectively contribute to an enhancement in durability under moderate service conditions.  
The results also revealed that the addition of NHL 5 lime in combination with latex and rubber, leads to faster and more evident microstructural changes, indicating a possible long-term structural vulnerability despite the increased mechanical strength. This observation is of particular importance in applications where flexibility and stability over time are more valuable than initial stiffness. Furthermore, the study emphasizes that T\({}_{2}\) distributions can be used as a diagnosis tool to ascertain the nature of water (free, loosely or strongly bound) and pore size, which is imperative information in optimizing mortar recipes. The application of the CONTIN algorithm for the inversion of the Laplace transform enabled the identification of continuous relaxation time distributions; however, it was also noted that the algorithm was highly sensitive to noise, which necessitates caution when interpreting the data.  
The incorporation of waste rubber into mortar compositions is a practice that aligns with the principles of a circular economy, whilst concurrently facilitating the development of functional materials that are customized to meet the requirements of sustainable construction. Consequently, optimized formulations derived from NMR results can deliver sustainable solutions for flooring utilized in the context of animal husbandry, exhibiting both structural and animal welfare benefits.  
Future studies will explore the mechanical performance under real farm conditions to validate the microstructural predictions obtained through NMR.  
In conclusion, the NMR method has been demonstrated to be a valuable tool for research and quality control in the field of construction materials, contributing to a deep understanding of hydration mechanisms and to the design of efficient, sustainable and environmentally friendly recipes.  
**Author Contributions**: Conceptualization, M.I.M., R.I. and T.P.T.; Methodology, M.I.M. and T.P.T.; Software, R.F.; Formal analysis, M.I.M., E.J. and R.F.; Investigation, M.I.M. and R.I.; Resources, M.I.M., E.J. and R.F.; Writing--original draft, M.I.M.; Writing--review & editing, M.I.M., R.I. and T.P.T.; Visualization, R.I. and T.P.T.; Supervision, D.L.M., E.J., R.I., R.F. and T.P.T.; Project administration, M.I.M. All authors have read and agreed to the published version of the manuscript.  
**Funding**: This research received no external funding.  
**Data Availability Statement**: The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding authors.  
**Conflicts of Interest**: The authors declare no conflict of interest.