Methodology for Analysis of the Reactivity of Coal Fly Ash Using Selective Dissolution by Hydrofluoric Acid

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The use of some additions as cement replacement has played an important role in the amount of clinker reduction. Due to its huge worldwide availability one of the most important and recognised replace agent is the fly ash, but is also estimated that only 30 to 40% of fly ash is used, although there are some challenges to be overcome, such as the reactive potential quantification. Chemical analysis is typically determined by the oxides content and does not take into account the vitreous and crystalline phase ratio. Therefore, this paper describes in detail one selective dissolution method, based in the hydrofluoric acid attack, to the quantification of the vitreous phase (reactive) and crystalline phases (not reactive). Fly ash from Portuguese Pego thermoelectric power plant was submitted to different attacks. To confirm the method and its effects, chemical and physical analysis were performed, such as STA, XRF, XRD with Rietveld refinement, SEM, EDS and laser diffraction granulometry. The results can be used to quantify the potential reactivity of this type of fly ash. The best results were achieved with 1% hydrofluoric acid attack during 6 hours.

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Periodical:

Edited by:

Matteo Colombo, Marco di Prisco

Pages:

1126-1133

DOI:

10.4028/www.scientific.net/KEM.711.1126

Citation:

R. Reis et al., "Methodology for Analysis of the Reactivity of Coal Fly Ash Using Selective Dissolution by Hydrofluoric Acid", Key Engineering Materials, Vol. 711, pp. 1126-1133, 2016

Online since:

September 2016

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$38.00

* - Corresponding Author

[1] EN 450-1: Fly ash for concrete. Part 1: Definition, specifications and conformity criteria (in Portuguese) (2012).

[2] Chancey, R.T. 2008. Characterization of crystalline and amorphous phases and respective reactivities in a class F fly ash. Austin, University of Texas at Austin.

[3] Rocha Junior, C.A.F. et al. 2012. Zeolite synthesis from boilers fly ash: physical, chemical and mineralogical characterization (in Portuguese). Cerâmica 58(345) 43-52.

[4] Fernández-Jiménez, A. and Palomo, A. 2003. Characterisation of fly ashes. Potential reactivity as alkaline cements. Fuel 82(18) 2259-2265.

DOI: 10.1016/s0016-2361(03)00194-7

[5] Arjuan, P., Silbee, M.R. and Roy, D.M. 1997. Quantitative determination of the crystalline and amorphous phases in low calcium fly ashes. In H. Justnes ed. Proceedings of the 10th International Congress on the Chemistry of Cement, Gothenburg, Sweden, June 2-6, 1997. Göteborg, [Sweden], Amarkai AB and Congrex. pp.2-6.

[6] Ibáñez, J. et al. 2013. Quantitative Rietveld analysis of the crystalline and amorphous phases in coal fly ashes. Fuel 105 314-317.

DOI: 10.1016/j.fuel.2012.06.090

[7] Fernández-Jimenez, A. et al. 2006. Quantitative determination of phases in the alkali activation of fly ash. Part I: potential ash reactivity. Fuel 85(5-6) 625-634.

DOI: 10.1016/j.fuel.2005.08.014

[8] Criado, M. et al. 2007. An XRD study of the effect of the SiO2/Na2O ratio on the alkali activation of fly ash. Cement and Concrete Research 37(5) 671-679.

DOI: 10.1016/j.cemconres.2007.01.013

[9] Aughenbaugh, K.L., Williamson, T. and Juenger, M.C.G. 2014. Critical evaluation of strength prediction methods for alkali-activated fly ash. Materials and Structures 48(3) 607-620.

DOI: 10.1617/s11527-014-0496-z

[10] Belie, N.D. et al. 2015. Determination of the degree of reaction of fly ash in blended cement. In C. Shi and Y. Yao eds. 14th International Congress on the Chemistry of Cement (ICCC2015). Beijing, Elsevier. 1 - 12.

[11] Palomo, Á., Alonso, S. and Fernandez-Jiménez, A. 2004. Alkaline activation of fly ashes: NMR study of the reaction products. Journal of the American Ceramic Society 87(6) 1141-1145.

DOI: 10.1111/j.1551-2916.2004.01141.x

[12] Fernández-Jiménez, A. et al. 2006. Quantitative determination of phases in the alkaline activation of fly ash. Part II: degree of reaction. Fuel 85(14–15) 1960-(1969).

DOI: 10.1016/j.fuel.2006.04.006

[13] EN 196-2: 2006 cements test methods. Part 2: Chemical analysis of cement (2006).

[14] Filho, J. 2008. Systems Portland cement, fly ash and hydrated lime: hydration mechanism, microstructure and carbonation of concrete (in Portuguese). Engenharia civil. Universidade de São Paulo.

[15] ASTM 2007. C 1585 – 04. Standard Test Method for Measurement of Rate of Absorption of Water by Hydraulic-Cement Concretes. Portland, ASTM International.

[16] Zhu, H., Zhang, Z., Zhu, Y. and Tian, L. 2014. Durability of alkali-activated fly ash concrete: chloride penetration in pastes and mortars. Construction and Building Materials 65(2014) 51-59.

DOI: 10.1016/j.conbuildmat.2014.04.110

[17] Criado, M., Fernández-Jiménez, A. and Palomo, A. 2010. Alkali activation of fly ash. Part III: Effect of curing conditions on reaction and its graphical description. Fuel 89(11) 3185-3192.

DOI: 10.1016/j.fuel.2010.03.051

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