Influence of carbon nanotubes and polycarboxylate superplasticiser on the Portland cement hydration process

Abstract

The aim of this study was to investigate the changes in the heat of hydration of Portland cement in case of its modification by a complex admixture (CA) based on multi-walled carbon nanotubes/carboxymethyl cellulose (MWCNT/CMC) suspension and polycarboxylate ether (PCE) plasticiser. The application of the CA leads to the prolongation of the duration of the induction, acceleration and later appearance of the peak at deceleration periods of Portland cement hydration by 4 h 55 min, 15 h 45 min and 21 h 30 min, respectively. The CA decreases the heat flow of cement by 35% in the acceleration period and total hydration heat emission by 26% after 48 h. The CA decreases the formation of portlandite and ettringite while the stability of gypsum increases. The identified tendency of changes in formed hydrates explains the retardation of C3S hydration. The evaluation of the cement hydration rate during the acceleration period by the angle of the linear function of the cement hydration heat flow curve was proposed. The cement modified by the CA can be useful in construction practice for the concreting of massive structures where low heat emission is a requirement, for the development of the mixture for new concrete technologies like massive concrete structures, hot weather concreting etc.