The effect of carbon nanotubes on mechanical properties of structural lightweight concrete using LECA aggregates

According to the latest studies, nanoparticles are the best additive materials to improve concrete's mechanical properties. Among these nanoparticles, Carbon Nanotubes (CNTs) are famous for their extreme tensile strength and flexibility. These particles can be used as a reinforcement to increase the mechanical properties of concrete. In the present study, the effects of using CNTs with different dosages were investigated on structural lightweight concrete's mechanical properties. Structural Lightweight Expanded Clay Aggregates (LECA) were used in the mixture of Structural Lightweight Concrete (LWC) as a substitute for coarse aggregates. Along with LECA, CNTs as a partial replacement for cement with varied weight ratios were added to the lightweight concrete (0.02, 0.1, and 0.3 percent of cement weight). The effects of carbon nanotubes on fresh concrete performance, water absorption, compressive strength, tensile strength, and flexural strength of 7-and 28-day lightweight concrete were carried out. The results indicate that the presence of 0.02% of cement weight of CNTs increased compressive strength, tensile strength, and flexural strength of the 28-day-old lightweight concrete up to 29%, 44%, and 26%, respectively. Moreover, it reduced the water absorption of lightweight concrete by 28.3%. Utilizing more content of CNTs resulted in less mechanical properties. Having done experimental tests, nanoparticles and cementitious materials bonding have been visualized by Scanning Electron Microscopy (SEM) device.