Influence of multi-walled carbon nanotubes on the residual performance of concrete exposed to high temperatures

Residual mechanical properties of lightweight concrete (LWC) and normal strength concrete (NSC) containing multi-walled carbon nanotubes (MWCNTs) after exposure to high temperatures are presented. Mechanical properties such as compressive strength (f'c,T), tensile strength (f't,T), stress-strain response, compressive toughness (Tc) and mass loss of the analyzed formulations were studied and have been elaborately discussed. A heating ramp of 5 °C per minute was selected to expose the cylindrical specimens to target temperatures up to 800 °C. The test data indicated that the inclusion of nano-reinforcements in concrete can significantly improve the residual mechanical properties. Morphological changes in microstructure, crack formation and interfacial interaction between aggregate and mortar were studied using scanning electron microscopy (SEM). Furthermore, the data obtained from high temperature material property tests were utilized to develop mathematical relationships for expressing residual mechanical properties of CNTs modified concrete as a function of temperature.