# Effect of Human Hair Fibers on the Performance of Concrete Incorporating High Dosage of Silica Fume
## 5 Conclusions  
The goal of this study was to investigate the mechanical properties of human hair fiber concrete made with human hair as a fiber and SF as a cementitious additive to find a solution to the adverse effects of high cement usage in the construction industry, which is one of the significant sources of pollution. The following conclusions can be drawn from the findings:  
* Using human hair in concrete enhances the ductility of the material by minimizing the formation of macro cracks by crack bridging effect.
* Test results suggest that using 2% human hair fiber and replacing 15% of the cement with SF produces the best flexure, compression, and split tensile strengths.
* The optimum fiber and SF dosages were found to be 2% and 15%, respectively, based on experimental and RSM results. Due to the amalgamation of fibers, the results at larger dosages were conflicting.
* To see if the predictive models were statistically significant, researchers utilized a two-way ANOVA with a significance level of less than 0.05 \(p\)-value. The residual error and pure error from the lack of fit are insignificant. The adjusted and expected R2 indicate that the predictive model accurately reflects the variable-response relationship and is suitable for testing.
* A linear equation was proposed to relate the compressive strengths of SF and human hair fiber in human hair fiber concrete. The RSM model and equations utilized to calculate human hair fiber concrete's compressive, split tensile, and flexural strengths were accurate. The prediction model results validate the experimental data, revealing a slight variance.
* The use of human hair and silica fume could reduce the environmental impact of concrete; however, a lifecycle assessment should be carried out to assess the actual potential environmental benefits.  
Conceptualization, M.A.; methodology, M.A.; software, M.A. and Z.H. validation, M.A. and Z.H.; formal analysis, M.A.; investigation, M.A.; resources, T.U.; data curation, Z.H. and T.U.; writing--original draft preparation, M.A., Z.H. and T.U.; writing--review and editing, H.P. and G.O.; visualization, M.A.; supervision, H.P. and G.O.; project administration, H.P. and G.O. All authors have read and agreed to the published version of the manuscript.  
This paper was supported by the Second Tibetan Plateau Scientific Expedition and Research Program (STEP) (Grant No. 2019 QZKK0902) and the National Natural Science Foundation of China (Grant No. 42077275). It was also supported by the Youth Innovation Promotion Association of the Chinese Academy of Sciences (2018405).  
Not applicable.  
The data are available on request to the corresponding author.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample** & **Human Hair** & **Silica Fume** & **Compressive** & **Flexural** & **Splitting** \\  & **Fiber (HHF \%)** & **(SF \%)** & **Strength** & **Strength** & **Strength** \\  & & & **(MPa)** & **(MPa)** & **(MPa)** \\ \hline
1 & 2 & 15 & 21.45 & 2.94 & 2.78 \\ \hline
2 & 2 & 15 & 21.44 & 2.94 & 2.78 \\ \hline
3 & 2 & 15 & 21.45 & 2.96 & 2.8 \\ \hline
4 & 2 & 30 & 15.6 & 2.08 & 2.02 \\ \hline Mean & - & - & 19.985 & 2.75 & 2.595 \\ \hline \hline \end{tabular}
\end{table}
Table 8: Summary of Optimization Mix.