## 5 Conclusions  
Herein, an experimental plan was executed to assess the effects of fiber dosage and length on the mechanical strengths of concretes. In addition, compressive, indirect-splitting-test tensile, and flexural (or modulus of rupture) strengths were evaluated. The conclusions of this study are as follows:  
1. There is no statistically significant correlation between the compressive strength of the PPFRC with fibers' volume or length. Furthermore, the results show that the strength values of each type of concrete with fibers do not differ statistically from the strength value of concrete without fibers;
2. Reinforced concrete with PP fiber lengths of 50 and 60 mm exhibits increases of 34% and 35%, respectively, in splitting-test tensile strength when the dosage is at 1.20%, which is equivalent to an increase of 0.27 and 0.30 MPa for each 0.40% increase in fiber dosage. Concrete manufactured with 40 mm fibers has a less than 22% strength increase. Fiber-reinforced concrete with volumes of 0.80 and 1.20% exhibits increases of 0.104 MPa and 0.157 MPa for every 10 mm increase in fiber length. Concrete reinforced with 0.40% does not present a statistically significant increase;
3. Reinforced concrete with fiber lengths of 60 mm shows an increase of 3.80, 8.46, and 12.09% when the dosage is 0.4, 0.8, and 1.20%, respectively, in the modulus of rupture. The 40 and 50 mm mixtures do not show statistically significant increases. On the other hand, mixtures with dosages of 0.40 and 0.80% exhibit increases of 4.41 and 4.60% for every 10 mm increase in fiber length. The mixtures with a fiber dosage of 0.40% do not show statistically significant increases;
4. As a result of this study, Equations (4)-(7) are presented, which allow prediction of the tensile strength by split test, and the modulus of rupture as a function of the strength of concrete without fibers, dosage of fibers, and length of fibers.  
The results of this study were based on the experimental results with variables and specimens defined herein. Therefore, further experimental studies that include more amplitude in the variables used, such as compressive strengths, fiber volumes, and slenderness ratios, are recommended to provide a broader range of analyzed cases with their respective conclusions.  
Figure 21: The ratio of the theoretical to experimental values of the modulus of rupture (\(y\)-axis) and compressive strength (\(x\)-axis) of PPFRC.  
**Author Contributions:** Conceptualization, A.A.D.S. and D.L.T.; resources, project administration, funding acquisition, writing--review and editing, A.A.D.S.; supervision, A.A.D.S. and D.L.T.; methodology, validation, formal analysis, data curation, D.L.T.; investigation, writing--original draft, D.L.T. and J.P.C.; visualization, J.P.C. All authors have read and agreed to the published version of the manuscript.  
This work was supported and funded by the Institute of Scientific Research of the Universidad de Lima (IDIC) (grant numbers PI.71.001.2020) and conducted by the Civil Engineering Department at the same university.  
The data supporting the findings of this study are available within the article.  
The authors declare no conflict of interest.