Mechanical Characterization of Concrete Reinforced with Different Types of Carbon Nanotubes

The main purpose of this study is to characterize the mechanical properties of concrete reinforced with carbon nanotubes (CNT). For this, an extensive experimental program was carried out involving the production and characterization of concrete mixes with five types of CNT, in terms of flexural, splitting tensile and compressive strength, ultrasonic pulse velocity, elastic modulus and fracture toughness. The dispersion ability of CNT in a wide range of pH aqueous suspensions was evaluated prior to their incorporation in concrete. It was found that 0.05–0.1% of CNT were effective to improve all tested properties, increasing the compressive, flexural and splitting tensile strength, as well as the fracture energy and elastic modulus up to 23%, 18%, 27%, 42% and 15%, respectively. The CNT showed great potential to improve the crack resistance and the fracture toughness of concrete, especially in the pre-peak performance of concrete. In relative to other types of CNT, concrete containing higher dosages of lower aspect ratio CNT had the highest improvement of mechanical strength. This is explained by the lower structural damage and higher dispersion capacity of this type of CNT in high pH environments. Nevertheless, higher aspect ratio CNT showed better contribution for the fracture energy, due to their more efficient bridging effect.