Toward improving carbon nanotube utilization in Portland cement mortar using novel processing techniques

Carbon nanotubes have the potential to enhance the strength, toughness, and self-sensing ability of Portland cement mortar and concrete. Two processing methods were studied to improve the dispersion and bonding of carbon nanotubes in cementitious composites. In the first method, silica functional groups were covalently bonded to carbon nanotubes before dispersing them in the mixing water. Two silica morphologies were used separately. Initially, agglomerated nanosilica spheres were produced, and later a semi-uniform coating was attached to the CNT surface. The flowability of the resulting Portland cement mortar mixtures was quantified and their flexural strengths were determined at various ages. Results indicate improvements to workability when the functional groups are used, but no change in flexural strength from mixtures containing pristine carbon nanotubes. Preliminary study was also performed on cement clinker with carbon nanotubes grown on it. The modified clinker was mixed into cement paste to observe the dispersion and test the hydration kinetics of the mixture. The particles clumped together within the specimen and the dense coating of carbon prevented hydration at the surface of the particles