Belite Cement Clinker from Coal Fly Ash of High Ca Content. Optimization of Synthesis Parameters

Guerrero, A.; Goñi, S.; Campillo, I.; Moragues, Amparo

doi:10.1021/es0351589

Cited by 76 publications

(65 citation statements)

References 8 publications

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“…The belite cements were then obtained by heating the precursors at 800 °C. More details regarding characterization of the precursors and the fabrication process can be found in the literature [15,17].…”

Section: Raw Materialsmentioning

confidence: 99%

“…Among the methods used for activating belite cements are those based on current cement technology: (i) the use of the most reactive low-temperature a' L polymorph (orthorhombic symmetry), which is stabilised during clinker production by rapid quenching of the clinker and the introduction of impurity ions (alkalis, Fe, Al sulphate, and so on) into the crystal structure during formation [3][4][5][6], (ii) the use of lowtemperature processes, which increase the surface area of C2S and therefore its reactivity [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23], and (iii) the addition of nano-materials during hydration [24][25][26].…”

Section: Introductionmentioning

confidence: 99%

“…The precursors are then dehydrated by heating without grinding at temperatures ranging from 500 to 900 °C [7][8][9]; with this process, it is possible to achieve BET-N 2 surface areas between 7 and 13 m 2 g _1 . Another low-temperature process is based on the formation of high-surface area precursors by hydrothermally treating the appropriate raw materials [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26].…”

Section: Introductionmentioning

confidence: 99%

“…Using the aforementioned procedure, we obtained belite cements (referred to as fly ash belite cement (FABC)), in which fly ash from coal combustion (class F [11][12][13][14] or class C [15][16][17][18][19][20][21][22][23][24][25][26]) was used as the raw material. The common technical characteristics of the cements are as follows: (i) the a'L-Ca2Si04 polymorph is as the main component, (ii) it contains elements, such as Fe, Al, Mg, Na and K, that increase its reactivity, (iii) it does not need to be ground, (iv) it can be used directly as cement without additional CaSOzt, since this is contained in the fly ash, and (v) it has excellent durability against the very concentrated salts that accompany low level radioactive waste (LLW) [14,[19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

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Study of alkaline hydrothermal activation of belite cements by thermal analysis

Goñi

Guerrero

2009

J Therm Anal Calorim

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The effect of alkaline hydrothermal activation of class-C fly ash belite cement was studied using thermal analysis (TG/DTG) by determining the increase in the combined water during a period of hydration of 180 days. The results were compared with those obtained for a belite cement hydrothermally activated in water. The two belite cements were fabricated via the hydrothermal-calcination route of class-C fly ash in 1 M NaOH solution (FABC-2-N) or demineralised water (FABC-2-W). From the results, the effect of the alkaline hydrothermal activation of belite cement (FABC-2-N) was clearly differentiated, mainly at early ages of hydration, for which the increase in the combined water was markedly higher than that of the belite cement that was hydrothermally activated in water. Important direct quantitative correlations were obtained among physicochemical parameters, such as the combined water, the BET surface area, the volume of nano-pores, and macro structural engineering properties such as the compressive mechanical strength.

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Section: Raw Materialsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Study of alkaline hydrothermal activation of belite cements by thermal analysis

Goñi

Guerrero

2009

J Therm Anal Calorim

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“…Some authors have obtained reactive belite phases containing sulphur (8); others have developed alternative production methods involving temperatures below 1350 ºC (e.g. hydrothermal synthesis followed by calcination at a moderate temperature) (9).…”

Section: Introductionmentioning

confidence: 99%

Clínqueres Pórtland Belíticos. Síntesis y Análisis Mineralógico

Torre¹,

Aranda²,

Aza³

et al. 2005

Bol. Soc. Esp. Ceram. Vidr.

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has been taken into account to design five compositions of belite Portland clinkers with belite (Ca 2 SiO 4 ) contents ranging from 60 to 65 wt%, located in its primary phase field of crystallization. The synthesis of these belite clinkers has been studied by high temperature microscopy, dilatometry, differential thermal analysis and thermogravimetric analysis. As a result, the optimum clinkerization temperature has been established at 1360 ± 5ºC. The quantitative phase analyses of the clinkers were carried out by X-ray powder diffraction with the Rietveld methodology. The mineralogical composition depends on the initial dosages, on the highest temperature achieved and on the time of residence at this temperature. The reaction was completed at 1365ºC during 15 min (free CaO <0.5 wt%), in those conditions the β-belite form is stabilized and the harmful transformation β→γ is avoided. Keywords: Belite Portland clinkers, Phase Equilibrium Diagrams, Rietveld Method Clínqueres Pórtland Belíticos. Síntesis y Análisis Mineralógico.Teniendo en cuenta el sistema cuaternario CaO-SiO 2 -Al 2 O 3 -Fe 2 O 3 , se han diseñado cinco composiciones de clínqueres Pórtland belíticos, con contenidos del 60 y del 65% en peso de belita (Ca 2 SiO 4 ), situadas en su campo primario de cristalización. La síntesis de estos clínqueres belíticos se ha estudiado "in situ" por microscopía de alta temperatura, dilatometría y análisis térmico diferencial y termogravimétrico. La temperatura óptima de clinquerización, determinada con estas técnicas, ha sido de 1360 ± 5ºC. Los análisis cuantitativos de los clínqueres se llevaron a cabo por difracción de rayos-X con la metodología Rietveld. Los porcentajes de las diferentes fases dependen de las dosificaciones iniciales, de la temperatura alcanzada y del tiempo de residencia a dicha temperatura. Se ha conseguido una reacción total (%CaO libre < 0.5% en peso) tratando a 1365ºC durante 15 min, en cuyas condiciones se estabiliza la forma β de la belita y se evita la transformación perjudicial β→γ.Palabras clave: Clínqueres Pórtland belíticos, diagramas de equilibrio, método de Rietveld.

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Effect of Nanosilica Additions on Belite Cement Pastes Held in Sulfate Solutions

Dolado¹,

Campillo²,

Erkizia³

et al. 2009

Progress in Nanotechnology

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Fly Ash Belite cement (FABC) pastes with and without nanosilica additions have been prepared and maintained in sulfate solutions (Na 2 SO 4 0.5 M) for 180 days. The mechanical performance and the changes in microstructure have been monitored at 28, 90 and 180 days by compressive strength, X-ray diffraction (XRD) and 29 Si MAS NMR measurements. We have found that, unexpectedly, and contrary to what happens in Ordinary Portland Cements (OPC), the addition of nanosilica particles induces an initial fall in the compressive strength of the samples. Only in samples maintained for long time (180 days), do the nanosilica addition improve the mechanical properties. Our XRD and 29 Si NMR experiments have revealed that although the nanosilica additions trigger the consumption of Belite phases, this is not always accompanied by formation of longer Calcium-Silicate-Hydrate (C-S-H) gel structures. Only at long time (180 days), and due to a mechanism that seems to be controlled by the pH of the samples, do the nanosilica additions lead to high polymerized C-S-H gels.Keywords: cement-based materials, nanomaterials, mechanical properties, microstructureThe authors gratefully acknowledge the financial support by the Spanish Government (Projects no. MAT 2002-04023-CO1-CO2-CO3 and MAT2005-03890). (1) IntroductionBelite cements (BC) are nowadays receiving a great deal of attention by the scientific community due to the low CO 2 emissions produced during their fabrication. Recently a new pathway based on the additions of nanoalumina has been explored to achieve faster strength gains. 6 Although in Ordinary Portland Cements (OPC) the beneficial effect of adding nanoparticles has been studied for some time, 7-10 in the case of Belite cements, to the best of our knowledge, no other work that previously mentioned Ref.[6] has been presented.In OPCs, the nano-SiO 2 and nano Al 2 O 3 particles serve as surplus source of Si and Al atoms so that C-S-H gels can grow further and yield improved mechanical properties. 7 Whether something akin occurs in Belite cements is unclear. On the one hand, Belite cements develop pore-solution with lower pHs (about 11-12) than that of OPCs (about 13-14) during the hydration process, fact clearly connected to their lower calcium content (C 2 S versus C 3 S) and low (or lack of) portlandite (Ca(OH) 2 ) formation, among other things. This difference is of extreme importance if one is aware that the pH governs most of the aggregation/disaggregation mechanisms involved in nanoparticle solutions. On the other hand, the microstructure of FABC cement pastes is noticeably different to the one found in OPC pastes. Differently to the case of OPCs, where the C-S-H gel is the only hydrated product which contains Si atoms, the microstructure of FABC cement pastes also contain alumino-silicates and zeolite-like products which incorporate Si atoms into their structure. 11This works aims precisely to investigate the effect of nanosilica additions on the mechanical properties and the microstructure changes of FABC pa...

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Belite Cement Clinker from Coal Fly Ash of High Ca Content. Optimization of Synthesis Parameters

Cited by 76 publications

References 8 publications

Study of alkaline hydrothermal activation of belite cements by thermal analysis

Study of alkaline hydrothermal activation of belite cements by thermal analysis

Clínqueres Pórtland Belíticos. Síntesis y Análisis Mineralógico

Effect of Nanosilica Additions on Belite Cement Pastes Held in Sulfate Solutions

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