Effect of Elevated Temperatures on Mechanical Performance of Normal and Lightweight Concretes Reinforced with Carbon Nanotubes

An experimental program was developed to evaluate the effect of multi-walled carbon nanotubes (MWCNTs) inclusion on elevated temperature properties of normal weight concrete (NWC) and lightweight concrete (LWC). The mechanical performance was assessed by conducting material property tests namely compressive strength (f’_c,_T), tensile strength (f’_t,T), mass loss (M_T), elastic modulus (E_T), compressive toughness (T_c) and stress–strain response under unstressed and residual conditions in the range of 23°C to 800°C. The mechanical properties were measured by heating 100 × 200 mm cylindrical specimens to 200°C, 400°C, 600°C and 800°C at a heating rate of 5°C/min. Results show that the inclusion MWCNTs in cementitious matrices enhanced the fire endurance. The relative retention of mechanical strength and mass of concretes modified with MWCNTs was higher. The stress–strain response of specimens modified with MWCNTs was more ductile. Microstructural study of cyrofractured samples evidenced the homogenous dispersion of nano-reinforcements in host matrix. Furthermore, the data obtained from high temperature material property tests was utilized to develop mathematical relationships for expressing mechanical properties of modified mixes as a function of temperature.