# Green Manufacturing of UHPFRC Made with Waste Derived from Scrap Tires and Oil Refineries
## 4 Conclusions  
In this study, UHPFRC samples containing waste derived from scrap tires and oil refineries were tested. The ECAT particles were found to have a porous microstructure. Their additions absorbed free water on their surfaces and thus reduced the flow of fresh cement mixes by 17%. There is a gradual increase in the compressive and flexural strengths of the UHPFRC samples with an increasing RSF content, indicating the ability of RSF to disperse uniformly in concrete matrices. The replacement of cement with ECAT reduced heat developments by up to 16.5% at the end of the calorimetry test. The compressive strength of the ultrahigh-performance cement-based mix containing silica fume and fly ash was determined to be 155 MPa at the end of 28 days. However, this value was reduced by 17% when the cement was replaced with ECAT by up to 15%. There was no significant change in flexural strength, indicating that the brittleness of the mortar samples was reduced by a partial replacement of cement with spherical ECAT particles. The addition of RSF to the ultrahigh-performance cement-based mixes containing silica fume, fly ash, and ECAT was found to increase compressive strength by 30%. The UHPFRC mixes without any ECAT achieved compressive and flexural strengths of 187 and 26 MPa at the end of 28 days. The UHPFRC samples with a central notch underwent strain-hardening and -softening mechanisms in three-point bending conditions. Increasing ECAT additions in UHPFRC mixes did not affect the flexural behavior of such mixes modified with RSF by up to 2%. In contrast, there was a marginal decrease in the flexural strength of the 3% RSF-reinforced UHPFRC samples with an increasing amount of ECAT. Cement binds RSF and sand together in the UHPFRC matrix, and its replacement with pozzolanic materials only affected the tensile properties in the case of a higher volume of RSF (i.e., 3% by volume). The addition of ECAT reduced the cost and CO\({}_{2}\) emissions of the UHPFRC mixes by 7% and 15%, but its additions at higher doses affected the flow and strength gain properties of the concrete mixes in the early stages. The acquisition of scrap tires and the installation of recycling plants locally to recover steel fibers can open a new business market and significantly reduce economic and environmental impacts. These experimental findings suggest that the development of UHPFRC is feasible on a larger scale with the use of waste derived from scrap tires and crude oil refineries. Moreover, the extensive application of this environmentally friendly UHPFRC in bridge deck construction could help achieve the goal of being carbon neutral.  
Conceptualization, H.A. and M.M.; methodology, H.A. and M.M.; validation, M.M.; formal analysis, M.M.; investigation, H.A., M.M., L.H. and P.K.; resources, L.S. and A.K.; data curation, M.M., L.H. and P.K.; writing--original draft preparation, M.M.; writing--review and editing, P.N., L.S. and A.K.; visualization, M.M.; supervision, L.S.; project administration, H.A. and  
Figure 9: Different operations in the ground-to-gate process of the preparation of the S3E15 mix.  
M.M.; funding acquisition, H.A. and M.M. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Narodowa Agencja Wymiany Akademickiej (NAWA), grant numbers PPN/ULM/2020/1/00286 and BPN/ULM/2021/1/00120.  
Not applicable.  
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.  
The authors declare no conflicts of interest.