The development of more durable materials is crucial for ensuring user safety in construction, particularly under adverse conditions. Carbon nanotubes are currently being studied as components in civil engineering composites due to their high tensile strength, high modulus of elasticity, high failure temperature, and satisfactory electrical and thermal conductivity. These nanotubes can be either non-functionalized (CNT), the more conventional type, or functionalized (CNT-F).This study aims to evaluate and compare the thermomechanical properties of concrete with the addition of CNT and CNT-F, analysis that still has not been extensively covered in the literature. The results show that the addition of nanomaterials did not significantly impact the mechanical properties of the concrete, although CNT-F exhibited slightly better performance. At 300 °C, CNT-F concrete experienced a 26 % reduction in strength, compared to a 34 % reduction in the control concrete and a 57 % reduction in concrete with CNT. At 900 °C, all types of mixtures were degraded, showing no significant difference in performance. This behavior was expected, as carbon nanotubes deteriorate at around 600 °C and are no longer effective at higher temperatures. Additionally, this trend was observed in other mechanical properties, such as tensile strength. It was also found that dispersing the nanotubes uniformly within the concrete mixture remains a challenge, as they can concentrate in specific regions of the composite. Finally, it's important to note that incorporating nanotubes into concrete helps store carbon within the material, preventing its release into the atmosphere and thereby reducing environmental damage.