Does a tiny amount of dispersant make any change to refractory castable properties?

Oliveira, I. R.; Pandolfelli, V. C.

doi:10.1016/j.ceramint.2009.06.020

Cited by 16 publications

(6 citation statements)

References 5 publications

(10 reference statements)

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“…Nevertheless, the formation of metastable hydrates (CAH 10 and C 2 AH 8 ) can take place due to the high water availability in the curing environment. The CAH 10 and C 2 AH 8 conversion to C 3 AH 6 and Al(OH) 3 is pointed out by many authors [4,15,[18][19][20] as being responsible for spoiling some CAC properties, as these hydrates with lower density (1.72 and 1.95 g.cm -3 ) give rise to denser ones (2.42 and 2.52 g.cm -3 ), increasing the total porosity. Nevertheless, the continuous increase of the stable phases [C 3 AH 6 and Al(OH) 3 ] during the curing time offset the deleterious effect of CAH 10 and C 2 AH 8 transformation, resulting in high mechanical strength values after 15 days for the dispersant containing samples (Fig.…”

Section: Resultsmentioning

confidence: 99%

Physical properties and hydration evolution of dispersant containing calcium aluminate cement compositions for endodontic applications

Luz

Pandolfelli

2014

Cerâmica

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The purpose of this study was to evaluate the physical properties and hydration evolution of calcium aluminate cement (CAC) compositions containing an advanced dispersant. The compressive strength, dimensional change, apparent porosity and quantitative X ray diffraction analysis (XRD) of the cement pastes were carried out over 1-15 days of curing (with the samples immersed in distilled water) at 37 ºC. The addition of a polymeric dispersant to the selected CAC (Secar 71) resulted in higher, but suitable expansion of the cement samples, and improved uniaxial compressive strength reaching values in the range of 73-87 MPa after 15 days. Quantitative XRD results also showed that C3AH6 and Al(OH)3 were the main phases detected during the cement hydration process, but CAH10 and C2AH8 were also found due to the higher water availability in the curing environment. According to the attained results, it could be concluded that the dispersant containing calcium aluminate cement compositions have the potential to be used as endodontic materials.

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Section: Resultsmentioning

confidence: 99%

Physical properties and hydration evolution of dispersant containing calcium aluminate cement compositions for endodontic applications

Luz

Pandolfelli

2014

Cerâmica

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“…Calcium aluminate cements (CAC) are often used as binders for refractory materials due to their excellent properties, such as shock resistance and high temperature resistance [1,2]. When pure calcium aluminate cements are used for refractory castables, a certain amount of water-reducing agent is usually added, which has a dispersing and lubricating effect on the cement particles and improves the compatibility of the cement slurry.…”

Section: Introductionmentioning

confidence: 99%

Effects of Sodium Tripolyphosphate Addition on the Dispersion and Hydration of Pure Calcium Aluminate Cement

et al. 2023

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In this paper, the effect of a sodium tripolyphosphate (STPP) addition on the dispersion and hydration of pure calcium aluminate cement (PCAC) was investigated, and the corresponding mechanism of effect was studied. The effects of STPP on the dispersion, rheology, and hydration processes of PCAC and its adsorption capacity on the surface of cement particles were analysed by measuring the 𝜁-potential on the surface of cement particles, the changes in the concentrations of elemental P and Ca2+ ions in a solution at different STPP additions. The experimental results show that STPP easily complexes with Ca2+ ions to produce the complex [CaP3O10]3− adsorbed on the surface of cement particles, which changes the potential on the surface of cement particles and increases the electrostatic repulsive force between cement particles, thus improving the dispersion and rheology of cement. At the same time, the contact area between cement particles and water is reduced, which hinders the hydration process and makes the time of hydration process longer. A comprehensive analysis shows that the best effect of STPP on pure calcium aluminate cements is achieved when the addition of STPP is 0.2%. This study can provide a reference for the addition of water-reducing agents in refractory castables as well as improving the quality of refractory materials.

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“…The main sources of sodium impurities in refractories derive from the use of caustic soda in the Bayer process to access alumina from bauxite ore, as well as the addition of additives with a sodium counterion to modify the setting and hardening properties of the green refractory. The influence of sodium‐containing additives on the room‐temperature properties is strongly determined by their acidity and has been shown to have a dramatic effect . Much work has gone into the optimization of setting time and placing conditions of castables with the help of various additives.…”

Section: Introductionmentioning

confidence: 99%

“…The influence of sodium-containing additives on the room-temperature properties is strongly determined by their acidity and has been shown to have a dramatic effect. [6][7][8][9] Much work has gone into the optimization of setting time and placing conditions of castables with the help of various additives. Sodium citrate has been shown to form a gel with the ions from dissolved cement particles which hinders the subsequent precipitation of hydrates thereby acting as a retarder, 10,11 whereas the reaction of alkaline additives, such as sodium carbonate, accelerates hydrate precipitation by forming a nucleation substrate with the aluminate ions in solution.…”

Section: Introductionmentioning

confidence: 99%

Effect of Sodium on Microstructures and Thermoelastic Properties of Calcium Aluminate Cement–Bonded Refractories

et al. 2015

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The effect of sodium on refractory phase formation in a model Calcium Aluminate Cement-bonded refractory was investigated from 700°C to 1500°C. Sodium reacts with a-alumina to form sodium b-alumina (b-Al 2 O 3 ) via the intermediate NaAlO 2 . Formation of b-Al 2 O 3 disrupts the reaction path of calcia with alumina, delaying crystallization of calcium hexaluminate, CaOÁ6Al 2 O 3 , from 1350°C to 1500°C. b-Al 2 O 3 is also shown to reduce Young's modulus and delay sintering. The presence of NaAlO 2 and b-Al 2 O 3 result in an increase in internal friction. Increased linear expansion of up to 47% is observed when 1 wt% Na is added. The expansion is shown to scale with the amount of dopant with only 0.3 wt% Na leading to an additional 31% linear expansion. On cooling, the presence of bAl 2 O 3 can be demonstrated by a peak in internal friction between 1200°C and 1000°C which could be caused by Na + ion hopping along the spinel-like planes.

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Does a tiny amount of dispersant make any change to refractory castable properties?

Cited by 16 publications

References 5 publications

Physical properties and hydration evolution of dispersant containing calcium aluminate cement compositions for endodontic applications

Physical properties and hydration evolution of dispersant containing calcium aluminate cement compositions for endodontic applications

Effects of Sodium Tripolyphosphate Addition on the Dispersion and Hydration of Pure Calcium Aluminate Cement

Effect of Sodium on Microstructures and Thermoelastic Properties of Calcium Aluminate Cement–Bonded Refractories

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