Reinforcement bars in many cases are subjected to harsh environment besides the mechanical load. This environment has significant impact if offshore structures are considered, however, the concrete itself may affect the reinforcing bars. In terms of metallic materials those degradation mechanisms are well-described, on the other hand if composite materials are under consideration, the process is more complex and still requires investigation. In this chapter, research of the harsh environment on flexural behavior is described and quantified. Two different solutions were used to simulate harsh environment, e.g., alkaline and salty water, the research is conducted in elevated temperature.