A Study of the Dispersing Effects of Polycarboxylate-Based Dispersant on Fine Particles

Ohta, Akira; Uomoto, Taketo

doi:10.3151/crt1990.10.2_131

Cited by 18 publications

(19 citation statements)

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“…Eluent was NaOH of pH 12 containing 0.1 mol/L NaNO 3 . Based on the SEC data obtained and following the method described by Ohta et al , 15 the lengths of the main and side chains of the two PCE comb polymers were determined. An illustration of their molecular architectures to scale is presented in Fig.…”

Section: Materials and Experimental Proceduresmentioning

confidence: 99%

Ca²⁺‐Mediated Interaction Between Microsilica and Polycarboxylate Comb Polymers in a Model Cement Pore Solution

Lesti¹,

Ng²,

Plank³

2010

Journal of the American Ceramic Society

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Interaction between polycarboxylate (PCE) comb polymers and microsilica suspended in a highly alkaline, Ca2+‐loaded model cement pore solution was studied via zeta potential, adsorption, and paste flow experiments. Zeta potential measurements reveal that in an alkaline suspension, microsilica possesses a negative surface charge stemming from deprotonated silanolate groups. Addition of soluble calcium salts (e.g., CaCl2) was found to cause a charge reversal to positive, owing to the adsorption of Ca2+ ions forming a monolayer on the microsilica surface. Further experiments demonstrate that through Ca2+ mediation, anionic PCE graft polymers adsorb in high amount on the microsilica surface. Polymers possessing a stronger anionic character exhibit a higher affinity to the positive microsilica surface, and consequently, exercise a more powerful dispersing effect than PCE showing less anionic character. A model summarizing the processes occurring at the surface of microsilica in this fluid system is proposed. The study suggests that the high fluidity of concrete containing microsilica depends on the effective dispersion of microsilica, and not of cement.

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Section: Materials and Experimental Proceduresmentioning

confidence: 99%

Ca²⁺‐Mediated Interaction Between Microsilica and Polycarboxylate Comb Polymers in a Model Cement Pore Solution

Lesti¹,

Ng²,

Plank³

2010

Journal of the American Ceramic Society

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“…However, the search for superplasticizers suitable for these concretes has been mainly conducted by empirical testing (Artelt and Garcia 2008). So far, mechanistic investigations have been focused on the interaction between superplasticizer and cement or some kind of model powder like limestone or MgO (Ohta et al 2000;Banfill et al 2007), while other components have been regarded as inert (Yamada et al 2000;Banjad Pecur and Stirmer 2006). These approaches ignored that in cement pore solution, components other than cement such as silica fume, can develop a positive surface charge and may interact with anionic admixture molecules.…”

Section: Introductionmentioning

confidence: 99%

Effectiveness of Polycarboxylate Superplasticizers in Ultra-High Strength Concrete: The Importance of PCE Compatibility with Silica Fume

Plank

Schroefl

Gruber

et al. 2009

ACT

187

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Methacrylate ester as well as allylether based polycarboxylates (PCEs) were synthesized to plasticize pastes of cement and silica fume having a water/cement ratio of 0.22. Methacrylate ester copolymers were found to disperse cement well, whereas allylether copolymers are more effective with silica fume. Mechanistic investigations revealed that in cement pore solution, the surface charge of silica fume becomes positive by adsorption of Ca 2+ onto negatively charged silanolate groups present on the silica surface. This way, polycarboxylate copolymers adsorb to and disperse silica fume grains. Thus, mixtures of both copolymers were tested in cement-silica fume pastes. These blends provide significantly better dispersion than using only one polymer. Apparently, the surfaces of hydrating cement (here mainly ettringite) and silica fume are quite different with respect to their chemical composition. Therefore, PCEs with different molecular architectures are required to provide maximum coordination with calcium atoms present on these surfaces.

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“…As for VGP, the degree of weathering of fine powder is slightly higher than coarse powder in terms of chemical composition, but their MB adsorptions can be regarded as being on the same level from their respective mean values and standard deviations. The adsorption of a polycarboxylate-based dispersant per unit area of powders of the same types (i.e., powders with the same compositions) is reported to be constant [21]. If this applies to MB, then fine and coarse powders of VGP can be regarded as the same powder from the aspect of dispersant adsorption, but clay powder cannot be regarded as the same type as VGPs.…”

Section: Bet Specific Surface Area and Adsorptionmentioning

confidence: 99%

Concrete with high-purity volcanic glass fine powder manufactured from pyroclastic deposit

Tomoyose

Noguchi

Sodeyama³

et al. 2020

SN Appl. Sci.

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Volcanic deposits, which are pozzolanically reactive, have long been known to improve the durability of concrete. Nevertheless, it has also been pointed out that the use of a natural pozzolan as a supplementary cementitious material (SCM) can pose problems of low workability and slow strength development. Also, in addition, its composition and physical properties have large variety and variability. We have been conducting studies on the total utilization of volcanic deposits for applications suitable for respective properties by classifying them by floating speed difference and particle diameter. It is reported that sorting out particles less than 2.4 g/cm 3 by dry gravity classification and removal of smaller clay fraction by dust collector is technically effective to recover high purity volcanic glass from pyroclastic flow deposits called "Ito-Shirasu", which is a local name for pyroclastic flow deposits in Japan. In this study, concrete containing high-purity volcanic glass powders with different finenesses are investigated regarding fresh properties, strength development, chloride ion penetration and CO 2 reduction. As a result, it was found that volcanic glass powders made an excellent contribution to the improvement of flowability comparable to fly ash, the enhancement of strength comparable to silica fume, and the restraint of chloride ion penetration. Volcanic glass powders can also contrbute to the reduction of CO 2 emission because the content of Portland cement can be significantly reduced to obtain the same strength compared to concrete with 100% Portland cement. This study provides a possibility to produce high performance SCMs in volcanic regions worldwide from volcanic ejecta by sorting out a high purity volcanic glass by the same method.

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A Study of the Dispersing Effects of Polycarboxylate-Based Dispersant on Fine Particles

Cited by 18 publications

References 0 publications

Ca²⁺‐Mediated Interaction Between Microsilica and Polycarboxylate Comb Polymers in a Model Cement Pore Solution

Ca²⁺‐Mediated Interaction Between Microsilica and Polycarboxylate Comb Polymers in a Model Cement Pore Solution

Effectiveness of Polycarboxylate Superplasticizers in Ultra-High Strength Concrete: The Importance of PCE Compatibility with Silica Fume

Concrete with high-purity volcanic glass fine powder manufactured from pyroclastic deposit

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A Study of the Dispersing Effects of Polycarboxylate-Based Dispersant on Fine Particles

Cited by 18 publications

References 0 publications

Ca2+‐Mediated Interaction Between Microsilica and Polycarboxylate Comb Polymers in a Model Cement Pore Solution

Ca2+‐Mediated Interaction Between Microsilica and Polycarboxylate Comb Polymers in a Model Cement Pore Solution

Effectiveness of Polycarboxylate Superplasticizers in Ultra-High Strength Concrete: The Importance of PCE Compatibility with Silica Fume

Concrete with high-purity volcanic glass fine powder manufactured from pyroclastic deposit

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Ca²⁺‐Mediated Interaction Between Microsilica and Polycarboxylate Comb Polymers in a Model Cement Pore Solution

Ca²⁺‐Mediated Interaction Between Microsilica and Polycarboxylate Comb Polymers in a Model Cement Pore Solution