Effect of CNT and CNF loading and count on the corrosion resistance, conductivity and mechanical properties of nanomodified OPC mortars

In this study, the influence of the addition of carbon nanotubes (CNTs) and nanofibers (CNFs) and their dispersion on the corrosion behavior, bulk electrical resistivity and mechanical properties of nanomodified Portland cement mortars was investigated. The experimental determination of the mechanical properties of nanocomposites reinforced with CNFs at an amount of 0.1 wt% of cement, and CNTs at amounts of 0.1 and 0.5 wt% took place, through three point bending and uniaxial compression experiments. The electrical properties were measured using alternating current (AC) and following the two pole method. For the evaluation of corrosion resistance the corrosion potential (Ecorr) and corrosion current density (Icorr) were measured in specimens partially immersed in a 3.5 % NaCl solution, using the Linear Polarization Technique (LPR). The electrochemical mass loss was then calculated using Faraday's Law. The addition of 0.1 wt% CNTs and CNFs remarkably improves the flexural strength and the Young's modulus, while enhancing the bulk electrical conductivity of the mortar nanocomposites. The corrosion study shows the addition of 0.1 wt% CNTs and CNFs decreases the corrosion rate and significantly increases the resistance to corrosion by delaying the onset of the corrosion reaction.