Effect of MWCNT and PCE plasticizer on the properties of cement pastes

Abstract

Polycarboxylate ether (PCE) plasticizer possesses by high water-reduction capability of about 30-40%. Despite the superior water reduction capability, the high dosages of PCE may cause the bleeding in cement systems, which is not suitable for high workability and self-compacting concrete. The current research is devoted to the studying of multi-walled carbon nanotubes (MWCNT) suspension prepared in combination with PCE plasticizer on the rheological properties of cement pastes. The bleeding of cement pastes modified by different dosages of MWCNT was estimated as well. The increase of yield stress in 3.7 and 3.5 times was obtained for cement paste modified by MWCNT suspension in dosage of 0.12% by weight of cement (bwoc) in 5 and 120 min after cement paste mixing, respectively. The increase of plastic viscosity in 2.95 and 1.55 times was obtained for cement paste modified by MWCNT suspension in dosage of 0.12% bwoc in 5 and 120 min after cement paste mixing, respectively. Modification of cement pastes by MWCNT suspension in the dosage of 0.24 % bwoc led to the decrease of bleeding water volume by 21.7% in comparison with cement pastes modified only by PCE plasticizer.

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.…”

“…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].…”

“…Table 2 includes the amount of CMC in the volume of suspension due to the fact that pellets "Graphistrength CW 2-45" consisted of MWCNT and CMC (see the previous section). The particle size analysis and zeta potential measurements for MWCNT/CMC suspension after homogenisation were carried out by particle size and zeta potential analyser DelsaNano C from Beckman Coulter [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.…”