## 4 Conclusions  
The present study investigated the impact of waste powder glass as a cement replacement with natural fibers from the Phragmites australis plant on the performance of reinforced beams. The study evaluated five concrete mix designs, including a control mix with no glass or Phragmites australis (PA) fibers. The mixes contained varying percentages of PA fibers, ranging from 0% to 1.5%, and 10% of the cement was replaced with waste powder glass in all mixes. Superplasticizer (SP) was added to the mixtures to maintain a consistent slump. The mechanical properties of concrete, including compressive strength, ultrasonic pulse velocity (UPV), split tensile strength, and flexural strength, were examined to evaluate the structural performance of reinforced concrete (RC) beams. Based on this study, the following conclusions can be driven:  
* The addition of 10% powder glass in the concrete mixture resulted in an increase in density, compressive strength, and split tensile strength in all curing ages;
* The addition of 0.5%, 1%, and 1.5% PA fibers caused a decrease in density and compressive strength but an increase in UPV values, indicating good to excellent concrete quality ranging from 5.08 to 5.83 km/s;
* The incorporation of PA fibers decreased the compressive strength. As PA fibers percentages increased, the compressive strength decreased as well. It is noted that the  
Figure 15: Strain measurements for beams; (**a**) 10 kN load incrementation; (**b**) 20 kN load incrementation; (**c**) 30 kN load incrementation. highest compressive value was achieved for mix with 10% powder glass with 0% PA fibers (37.2 MPa). There is a high correlation between UPV and compressive strength with high coefficient of determination R\({}^{2}\) of 0.99;
* The addition of fibers may increase the split tensile strength due to the chemical treatment (NaOH) of PA fibers, which promotes better interaction between fibers and matrix, increasing the fiber surface roughness and bonding between them. The highest split tensile value was achieved for the addition of 10% glass with 0.5% PA fibers (3.4 MPa). Same trend was observed for flexural test results. The addition of 10% powder glass and 0.5% PA fibers achieved the highest value (8.8 MPa);
* The load deflection curves showed that the beam containing 10% powder glass and 0% PA fibers had the best performance in terms of load capacity (47.6 Mpa);
* The beam with 10% powder glass and 0.5% PA had the best performance in terms of ductility index (7);
* It is important to consider the proportion of PA fibers and any pretreatment used when creating mixtures of PA fibers and concrete. Based on the findings of this study, it can be concluded that the addition of powder glass and Phragmites australis fibers can improve the mechanical properties and durability of reinforced beams. These results can have practical implications for the construction industry, where the use of sustainable and eco-friendly materials is increasingly being emphasized. Furthermore, future studies could investigate the effect of different types and proportions of fiber and glass powders on the mechanical and durability properties of reinforced beams. Additionally, further research could explore the potential use of other natural fibers and recycled materials in combination with powder glass as reinforcements in concrete structures. Such studies could lead to the development of novel eco-friendly and sustainable construction materials with enhanced performance and reduced environmental impact. Conceptualization, J.K. and A.E. ; methodology, R.R. and A.J. ; formal analysis, A.J., H.E.-H. and R.R. ; writing-- original draft preparation, R.R. and A.J. ; writing-review and editing, J.K., H.E.-H. and A.J. ; supervision, J.K., A.E. and A.J. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. Data availability Statement: Data sharing is not applicable to this article. Authors would like to thank all technicians in Beirut Arab University lab.