Comparative study of two PCE superplasticizers with varied charge density in Portland cement and sulfoaluminate cement systems

Tian, Hongwei; Kong, Xiangming; Song, Tong; Wang, Dongmin

doi:10.1016/j.cemconres.2018.10.003

Cited by 98 publications

(39 citation statements)

References 66 publications

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“…36 specimens for BSEM) were put into a 100 g cold isopropanol (5°C) bath to terminate cement hydration and then sample was dried under nitrogen flow at atmospheric pressure. 38…”

Section: Test Methodsmentioning

confidence: 99%

“…In this study, the solvent exchange method with isopropanol was used to arrest hydration of cement . Samples (1g powder or fresh paste for XRD and TG or 0.5g cube specimens for BSEM) were put into a 100 g cold isopropanol (5°C) bath to terminate cement hydration and then sample was dried under nitrogen flow at atmospheric pressure …”

Section: Experimental Programmentioning

confidence: 99%

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A new hydration kinetics model of composite cementitious materials, part 1: Hydration kinetic model of Portland cement

et al. 2019

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This work is the first part of an overall research project that aims to model the hydration kinetics of modern composite cementitious materials. The aim of this part is to build a hydration kinetic model to characterize the hydration behavior of cement at all ages. In this paper, the nucleation and growth of CSH and the diffusion of water are described by a modified BNG model and a modified Jander's model. The kinetic parameters are obtained by simulative fitting of the model to the experimental data. The linear functions between the nucleation and growth rates and the W/C ratios are given in this paper. The apparent activation energy of the nucleation rate constant, growth rate constant, and generalized diffusion constant are approximately 36.0, 37.5, and 42.0 kJ/mol, respectively. Finally, the phase compositions of hardened cement paste are calculated according to the kinetic model and the reaction formula of cement.

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“…36 specimens for BSEM) were put into a 100 g cold isopropanol (5°C) bath to terminate cement hydration and then sample was dried under nitrogen flow at atmospheric pressure. 38…”

Section: Test Methodsmentioning

confidence: 99%

Section: Experimental Programmentioning

confidence: 99%

A new hydration kinetics model of composite cementitious materials, part 1: Hydration kinetic model of Portland cement

et al. 2019

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“…The zeta potential is highly sensitive to the chemical composition of the solvent such as ionic species, pH, and conductivity [23,24]. Many zeta potential measurements have been performed on cement particles [19][20][21][25][26][27][28][29][30][31]; measurements have been performed on OPCs, BFSCs [19,21,26,31], hydrated materials [20,25,28,29], and minerals for admixture [27,30]. Nevertheless, the data for UFC used in this study were not reported.…”

Section: Measurement Of Zeta Potentialmentioning

confidence: 99%

“…Nevertheless, the data for UFC used in this study were not reported. In addition, there are some cases wherein SPs were added to the system [28][29][30][31]; however, these were measured using an electroacoustic method in high-concentration systems [28][29][30] or different conditions of solution even in the case of diluted systems [31]. Therefore, it was necessary to measure the zeta potential under the conditions established in this experiment.…”

Section: Measurement Of Zeta Potentialmentioning

confidence: 99%

Application of Poly-γ-Glutamic Acid Flocculant to Flocculation–Sedimentation Treatment of Ultrafine Cement Suspension

Yanagibashi

Kobayashi

Omori

2019

Water

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We examined the effect of poly-γ-glutamic acid flocculant (PGAF) on the removal of ultrafine cement (UFC) particles stabilized by a poly-carboxylate co-polymer, which is a superplasticizer (SP). The flocculation–sedimentation treatment with PGAF successfully removed the SP-stabilized cement particles through the gravitational settling of the formed flocs. The removal efficiency reduced with the increase in the ionic strength, probably because of the shrunk form of poly-γ-glutamic acid (γ-PGA) at high ionic strengths. Increasing the mixing intensity during rapid mixing improved the removal efficiency. A series of flocculation–sedimentation experiments provided a diagram showing the relationship between ionic strengths and the addition amount of PGAF. Our results suggest that PGAF is a good candidate for the purification of cement suspension by flocculation–sedimentation, and a better removal performance can be obtained at lower ionic strengths with intense rapid mixing. From the diagram of the control charts presented in this study, we can determine the optimal addition amount of PGAF for achieving the target removal rate for cement suspension under any ionic strength.

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“…Therefore, the reason why the poly-phosphate could effectively enhance the dispersion, whilst the mono-phosphate failed cannot be simply explained by the retarding effect. One possible explanation might be attributed to the difference in the molecular structure of the phosphates, which could result in different performance at the water/solid interface during the very early-stage hydration [39][40][41][42], and this would further influence the adsorption layer [43][44][45]. As a consequence, the difference in PCE adsorption behavior could be expected in the presence of different phosphates.In this study, the dispersion mechanism of the PCE-phosphate system was investigated.…”

mentioning

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...

show abstract

Comparative study of two PCE superplasticizers with varied charge density in Portland cement and sulfoaluminate cement systems

Cited by 98 publications

References 66 publications

A new hydration kinetics model of composite cementitious materials, part 1: Hydration kinetic model of Portland cement

A new hydration kinetics model of composite cementitious materials, part 1: Hydration kinetic model of Portland cement

Application of Poly-γ-Glutamic Acid Flocculant to Flocculation–Sedimentation Treatment of Ultrafine Cement Suspension

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

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