Highly concentrated carbon nanotube admixture for nano-fiber reinforced cementitious materials

The use of effectively dispersed multiwalled carbon nanotube (MWCNT)/aqueous/surfactant suspensions in cement based materials have been shown to substantially improve their mechanical properties. The produced MWCNT suspensions have a high aqueous content, which corresponds to the mixing water. In the present work, a method for preparing highly concentrated MWCNT suspensions is presented, thus reducing the volume of the resulting admixture that is required in cement based materials. A centrifugal process, that uses two different ultracentrifuge rotors, was employed to reduce the quantity of water in the suspensions. Optical absorbance spectroscopy shows that the ultracentrifugation process increases the concentration of the MWCNT suspensions by a factor of 5. Using the highly concentrated MWCNT suspensions following dilution results in nanocomposites with mechanical properties that are comparable to the performance of samples prepared using the non-concentrated suspensions. These results verify that the ultracentrifugation concentration method successfully preserves the solubility of the MWCNT suspensions without affecting the reinforcing properties of the admixture. In this manner, the ultracentrifugation concentration method may constitute an effective preparation step for large-scale implementation of MWCNT admixtures. (C) 2012 Elsevier Ltd. All rights reserved.