The Effect of Dispersion Method of Nanotube Carbon on the Compressive Strength of Concrete

In recent years, the use of nanoparticles to improve the properties of concrete has created a new perspective in concrete technology. Carbon nanotube is one of the most promising nanomaterials available to improve the performance of concrete and cement due to their excellent mechanical properties and chemical stability. Due to the tendency of nanotubes to shrink and be hydrophobic, proper distribution and dispersion of carbon nanotubes in concrete will be very effective in achieving the desired mechanical properties of concrete. Therefore, in this study, carbon nanotubes became hydrophilic using surface modification and covalent bonding. For the durability and stability of carbon nanotubes in water, C-type surfactants (CTAB), sodium dodecyl sulfate (SDS), polyethylene glycol (PEG) and polycarboxylate (PCE) were used. The results of visible ultraviolet (UV-vis) spectroscopy and compressive strength tests performed on concrete showed that the combination of PEG and PCE surfactants caused the optimal dispersion of carbon nanotubes so that it is compatible with the cement matrix and leads improve the mechanical properties of concrete. Experimental results show that the compressive strength of concrete samples of 7, 14 and 28 days containing 0.015% (cement weight) of carbon nanotubes with PEG and PCE surfactant increased by 3.1, 7.4 and 14.14%, respectively, compared to the reference sample; While in concrete samples containing carbon nanotubes and CTAB surfactant, due to the incompatibility of CTAB with cement and the low stability of dispersion of carbon nanotubes with CTAB, the concrete compressive strength of 7, 14 and 28 days (compared to the reference sample) decreased by respectively 5.6%, 17% and 9%.