Capillary Absorption and Oxygen Permeability of Concrete Reinforced with Carbon Nanotubes

This article focuses on the transport properties of concretes reinforced with different amounts (0.05-0.5 wt.%) of pristine and functionalized carbon nanotubes (CNTs) with distinct aspect ratios (300, 667). To this end, concretes with different water-to-cement ratios were tested at distinct ages in terms of capillary absorption and oxygen permeability. The results show the ability of CNTs to decrease both capillary water absorption and oxygen permeability up to 42 and 71 %, respectively, depending on the type and amount of CNTs. Compressive strength increased up to 21 %. The best performance was found for 0.1 % CNTs of a lower aspect ratio. Higher amounts of CNTs did not lead to a proportional reduction of transport properties. CNTs were more effective in dried concrete compared to saturated ones where they could better participate in the pore refinement and microcrack retention. Transport properties correlated well with compressive strength, but oxygen permeability was greater affected by the incorporation of CNTs than other tested properties.