Mechanical Properties of Concrete, Reinforcing Steel, and CFRP under Low-Temperature Conditions

Abstract This study experimentally investigates the mechanical behavior of concrete, reinforcing steel, and carbon fiber reinforced polymer (CFRP) under low temperature exposure, covering a temperature range from −60 °C to 20 °C. Concrete specimens with various mix proportions and curing conditions were cast to evaluate the effects of temperature on compressive strength, elastic modulus, and compressive strain. Reinforcing steel and CFRP specimens were also tested to assess changes in tensile performance under low-temperature conditions. The results showed that both concrete and reinforcing steel exhibited increases in strength and stiffness as the temperature decreased. In the case of concrete, the rate of increase varied depending on the curing method and mix proportions, while for reinforcing steel, the strength increase remained generally consistent regardless of the nominal bar diameter. In contrast, CFRP demonstrated a reduction in both tensile strength and rupture strain with decreasing temperature. Furthermore, the applicability of existing concrete material models, Popovics and Hognestad models, was evaluated under low-temperature conditions. While both models provided reasonable predictions at room temperature, Popovics model more accurately reflected the mechanical behavior of concrete subjected to cold environments. These findings contribute to a better understanding of the material behavior under cold conditions and provide fundamental insights for future structural design and strengthening strategies considering low temperature exposure.