## 4 Conclusions  
Based on the previously described analysis and results, the CSFRC \"lifespan\" can be divided into three periods: childhood (1), the best life period (2), and the old age period (3). In the first life period, the tensile strength of CSFRC is much higher than that of normal concrete at the age of 28 days and almost twice that of UHPC, which enables significantly earlier utilization. However, it is important to consider that CSFRC in this life period is prone to significant damage, and its serviceability may be endangered. The second life period begins at the age of 21 days and lasts for around 30 days. In this period, CSFRC presents the best features and has significantly high ductile behavior. Upon further aging, CSFRC passes from the second to third life period, and this leads to the loss of some features, such as a decrease in the ductility.  
1. The hardening process is faster for CSFRC than normal concrete or UHPC, and CSFRC reaches full tensile strength at the age of 21 days.
2. Reinforcing concrete with carbon fibers contributes to the increase in elasticity modulus and prolongs the time of its development up to 21 days of age. Carbon fibers also prevent subsequent degradation of the elasticity modulus, e.g., between the 21 st and 91 st day of age.
3. The temporal development of CSFRC tensile strength, first crack strength, ultimate tensile strain, and elasticity modulus can be well estimated using the modified fib Model Code 2010 equations proposed in this work.
4. The tensile behavior of CSFRC significantly differs from that of unreinforced concrete, showing similarities with steel behavior. Hence, it can be estimated using a bi-lineardiagram through three points, especially in the second life period. However, in the first and third life periods, the bi-linear diagram through three points can underestimate damage in the CSFRC in the region between the stress level of the first nonlinearities and achieving the full tensile strength of CSFRC; hence, in these life periods, the four-point stress-strain curve is proposed as a material model.
* Concrete shrinkage has a significant influence on the CSFRC behavior over time, decreasing the ductility and energy dissipation capacity. In the linear region, it causes faster strain development, while in the nonlinear region, it reduces the damage capacity.
* Concrete shrinkage can also have a positive influence on CSFRC behavior, contributing to increased tensile strength and first crack strength in \"life periods\" 2 and 3.  
Conceptualization, A.D.; methodology, A.D. and P.L.; validation, A.D.; investigation, A.D.; writing--original draft preparation, A.D.; writing--review and editing, A.D., P.L., O.F. and G.S.; visualization, A.D.; supervision, O.F. and G.S. All authors have read and agreed to the published version of the manuscript.  
Open Access funding enabled and organized by Project DEAL: This research was funded by the German Research Foundation DFG as a part of the \"Priority Programme SPP 2020: Cycle deterioration of High-Performance Concrete in an experimental-virtual lab\" (Grant Numbers VO 829 /13-1, FI 1720/7-1, GF1664/13-1, PE 1464/6-1).  
Not applicable.  
Raw data are available from the authors upon request.  
The researchers express their gratitude to everyone involved in the priority program SPP 2020, as the working atmosphere between the groups is created by fruitful collaboration.  
The authors declare no conflict of interest.