Organic admixtures and cement particles: Competitive adsorption and its macroscopic rheological consequences

Bessaies-Bey, Hela; Baumann, Robert; Schmitz, Marc; Radler, Michael J.; Roussel, Nicolas

doi:10.1016/j.cemconres.2015.10.010

Cited by 94 publications

(43 citation statements)

References 32 publications

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“…e better plasticizing effect can be reached with the increase of zeta potential and decrease of surface tension and steric effect, which is determined by molecular parameters of monomers [29]. A number of research studies are devoted to the investigation of influence of plasticizing admixtures on the rheological properties of cement systems [30,31]. M.-H. Zhang et al compared the effect of three types of plasticizers such as lignosulphonate, polycarboxylate, and polynaphthalene, on the loss of workability of cement pastes.…”

Section: Introductionmentioning

confidence: 99%

Rheological Properties of Cement Pastes with Multiwalled Carbon Nanotubes

Skripkiūnas

Karpova

Barauskas

et al. 2018

Advances in Materials Science and Engineering

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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.

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Section: Introductionmentioning

confidence: 99%

Rheological Properties of Cement Pastes with Multiwalled Carbon Nanotubes

Skripkiūnas

Karpova

Barauskas

et al. 2018

Advances in Materials Science and Engineering

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“…The adsorption amount of PCE has been reported to determine the dispersion ability of PCE [26]. In the presence of retarder, competitive adsorption would happen between PCE and retarder; it meant that the adsorption process of PCE would be hindered by the addition of phosphate, which resulted in a decline in the dispersion [20,31,54]. The adsorption amount of PCE in the presence of TSP and SHMP was tested in order to confirm the competitive adsorption, and Figure 8 shows the results.…”

Section: Adsorption Amountmentioning

confidence: 99%

“…Generally, high fluidity can be easily achieved by incorporation of the comb-type copolymers, known as polycarboxylate superplasticizer (PCE) system [13][14][15][16], and this system consists of copolymers and retarders, rather than a single-component system [17][18][19]. In spite of being added as a supplementary material, retarders can significantly enhance the dispersion capacity of the superplasticizer system [20,21], and, in the real engineering practice, this has been widely employed. The generally believed reason is because the consumed free water and superplasticizer was reduced, as a result of the delayed hydration of cement minerals [22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Effect of Sodium Hexametaphosphate and Trisodium Phosphate on Dispersion of Polycarboxylate Superplasticizer

Zhang

Liu

et al. 2019

Materials

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Enhancement in dispersion of polycarboxylate superplasticizer (PCE) could be obtained by incorporating retarders in normal concrete. The generally believed reason was that the consumption of free water and polymer at the beginning was reduced by retarding cement hydration. This theory could not convincingly explain why sodium hexametaphosphate (SHMP) was able to promote the dispersion capacity of PCE, while trisodium phosphate (TSP) could not, despite that both TSP and SHMP could obviously retard the cement hydration. The adsorption behavior of PCE and phosphate was investigated and the mechanism was analyzed in order to gain deeper understanding. The results showed that TSP and SHMP delayed the cement hydration, impeded adsorption process of PCE, and increased thickness of adsorption layer. It was interesting that TSP reduced the dispersion, but SHMP enhanced. The reason for this contradiction was due to the difference in composition of adsorption layer. In the PCE-TSP system, this layer was composed of the precipitates (formed by TSP and Ca 2+ ) and the invalided PCE (caused by these precipitates in the immediate vicinity of the cement grains); the invalided PCE was due to the decrease of PCE dispersion. In the PCE-SHMP system, "Inner-phosphate (multi-layers) + Outer-PCE (single layer)" structure was formed to make the PCE work more effective, hence enhancing the dispersion. These results were expected to be useful for the design of highly efficient dispersants. dispersion capacity [26][27][28][29][30]. Based on this, the retarder might hinder the adsorption process of PCE and it was referred to as competitive adsorption [31][32][33][34][35], thereby reducing the dispersion. In addition, the thickness of the adsorption layer should also be accepted as a factor influencing the dispersion of PCE [36,37]. In spite of the decline in adsorption amount of PCE in the presence of retarder, as reported in previous study, the adsorption layer was obviously thickened to enhance the dispersion [37]. On the basis of discussion above, the conclusion could be made that the dispersion capacity of the PCE-retarder system should be associated with the retarding effect of retarder, adsorption behavior of PCE, and the thickness of the adsorption layer.Poly-phosphates, such as sodium tripolyphosphate and sodium hexametaphosphate (SHMP), have been widely used to promote the dispersion ability and dispersion retention ability of the superplasticizer system in real engineering practice. However, mono-phosphates, such as trisodium phosphate (TSP) and sodium hydrogen phosphate, cannot play the same roles as poly-phosphate in commercially available PCE products. If the retardation was the main reason for the enhancement, poly-phosphate and mono-phosphate would both have a similar effect on dispersion of PCE system, because both TPS and SHMP could retard the cement hydration [38]. Therefore, the reason why the poly-phosphate could effectively enhance the dispersion, whilst the mono-phosphate failed cannot be simply explained by the retard...

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“…Dynamic Light Scattering (DLS) is generally used to measure the size distribution by intensity of particles in a liquid medium. In this work, the measure scattered intensity was further used to estimate the concentration of particles remaining in the interstitial pore fluid after mixing [7,8]. This was done by first recording the scattered intensity.…”

Section: Dynamic Light Scattering Measurementsmentioning

confidence: 99%

Enhancing Printable Concrete Thixotropy by High Shear Mixing

Vandenberg

Bessaies-Bey²,

Wille

et al. 2018

RILEM Bookseries

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Our results show that the storage elastic modulus as a function of time increases at a higher rate for the cement paste mixed at higher versus lower mixing intensity. Hence, higher mixing appears to be enhancing thixotropy. Using calorimetry analysis we find that higher mixing decreases the setting time and enhances the peak of the heat flow. By analyzing the nanoparticles present in the suspending fluid of the cement paste, we show, in accordance with literature, that an appropriate combination of mixing energy and super-plasticizer dosage promotes hydration by scratching hydrates from the surface of cement particles, stabilizing them in the suspending fluid and hence generating additional nucleation surfaces. These results open the door for the design of printing heads including high-shear micro mixers allowing for a faster liquid-to-solid transition of the printable material.

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Organic admixtures and cement particles: Competitive adsorption and its macroscopic rheological consequences

Cited by 94 publications

References 32 publications

Rheological Properties of Cement Pastes with Multiwalled Carbon Nanotubes

Rheological Properties of Cement Pastes with Multiwalled Carbon Nanotubes

Effect of Sodium Hexametaphosphate and Trisodium Phosphate on Dispersion of Polycarboxylate Superplasticizer

Enhancing Printable Concrete Thixotropy by High Shear Mixing

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