Evaluation of the rheological behavior, hydration process, and mechanical strength of Portland cement pastes produced with carbon nanotubes synthesized directly on clinker

Abstract

Multi-walled carbon nanotubes (MWCNTs) have been incorporated in cementitious composites and important results in terms of rheological and mechanical performance have been obtained. Despite the current MWCNT dispersion procedures found in the literature, MWCNT synthesized directly on clinker is an alternative route to employ this nanomaterial in cementitious composites. It is also much more compatible with the procedures used by the construction industry. Based on this scenario, this study presents results in terms of rheological behavior, hydration process and mechanical strength of cement pastes (with a water/cement ratio of 0.4), produced with MWCNTs synthesized directly on clinker. The percentage of MWCNTs was equal to 0.15 and 0.30% with respect to cement content (bwoc). A reference paste without MWCNTs was also produced for comparison. In terms of the rheological behavior, the cement pastes with MWCNTs showed adequate performance for the application. It was also verified that MWCNTs promoted an increase in the cement hydration rate, reducing the initial setting time and changing the hydration period. This was most evident when the MWCNT rate was increased from 0.15 to 0.30% bwoc. With respect to compressive and tensile strength, the pastes with MWCNTs showed gains of 28% and 43% respectively at the age of 28 days for the 0.15% carbon nanotube content.