Rheological Properties of Cement Pastes with Multiwalled Carbon Nanotubes

Abstract

The evaluation of rheological properties of cement systems is getting more relevant with growing interest to self-consolidating concrete (SCC), high-performance concrete (HPC) and ultrahigh-performance concrete (UHPC). The rheology models are a perspective tool to predict and manage the properties of cement systems in the fresh and hardened state. The current research is focused on the rheological test of cement systems modified by multiwalled carbon nanotubes (MWCNT) dispersion with and without polycarboxylate ether (PCE). The content of dispersion with 1% concentration of MWCNT in cement pastes varied from 0.125 to 0.5% by weight of cement. The dosage of PCE was taken as 0.6% by weight of cement. The cement pastes were prepared based on Portland cement without mineral additives. The rheological test was carried out at 5, 30, 60, and 120 min after mixing of cement paste. The rheological test established that modification of cement pastes by MWCNT dispersion in dosage 0.25% leads to the decrease of yield stress by 30.7% and increase of plastic viscosity by 29.6%. The combined modification by PCE and MWCNT dispersion shows the decrease in plastic viscosity of cement pastes by 9.90% in dosage of MWCNT equal to 0.5% by weight of cement, reduction of water demand by 20% for the same workability, and decrease of yield stress till 0 Pa. It gives the ability to obtain the self-compacting mixtures. The cement pastes with and without MWCNT dispersion revealed the shear-thinning behavior during 120 min after mixing. The modification of cement pastes by PCE with and without MWCNT dispersion showed the shear-thickening behavior which remains during 120 min after mixing.

Rheological Properties and Flow Behaviour of Cement-Based Materials Modified by Carbon Nanotubes and Plasticising Admixtures

“…The understanding of rheological behaviour of the plasticised cement paste with MWCNT can be valuable for further design of complex admixtures based on MWCNT and Pl. The present research is a continuation of research works [27][28][29], which generalise the research data on the rheological properties and water bleeding of cement pastes modified by MWCNT/CMC suspension in the presence of three different Pl, with application of the Herschel-Bulkley model for approximation of the experimental data; a possible explanation of the action mechanisms of MWCNT in the plasticised cement pastes is also proposed.…”

“…Portland cement without mineral additives CEM I 42.5 R and with fineness by Blain of 3552 cm 2 /g, as a more widely used cement in construction practice, was used as a binder. The mineral composition and physical and mechanical properties of the applied cement are presented in the research [27].…”

“…The homogenisation of the MWCNT/CMC suspension was carried out for 6 min by ultrasonic homogeniser Bandelin Sonopuls HD 3400 (400 W, 20 kHz). The optimisation of the applied homogenisation processes was studied and described in the research works [27,28].…”

“…Ma et al [22] established an increase in yield stress and plastic viscosity of cement mortar modified by CNTs. Jiang et al [10] and Skripkiunas et al [27][28][29] observed an increase in yield stress and plastic viscosity of nanomodified cement paste as well. Opposite to these research works, Souza et al [23] and Paula et al [24] did not obtain any changes in rheology of the cement pastes and slurries prepared with CNTs synthesised on cement clinker.…”

“…In addition to flowability tests, it is necessary to provide rheological investigations to obtain, more deeply, an understanding of the action mechanisms of nanoadditives in cement systems. Some attempts to study the rheology of nanomodified cement pastes by the use of rheometers and rheological models were made [10,[22][23][24][25][26][27][28][29]. Ma et al [22] established an increase in yield stress and plastic viscosity of cement mortar modified by CNTs.…”