Alkali-activated fly ash. Relationship between mechanical strength gains and initial ash chemistry


  • G. Kovalchuk V.D. Glukhovskiy Scientific Research Institute on Binders and Materials, Kyiv
  • A. Fernández-Jiménez Instituto de Ciencias de la Construcción "Eduardo Torroja", CSIC, Madrid
  • A. Palomo Instituto de Ciencias de la Construcción "Eduardo Torroja", CSIC, Madrid



Fly ash, alkali activation, alkaline cements, high-strength cements, zeolites


Alkali-activated fly ash is the primary component of a new generation of high-strength, durable binders with excellent mechanical properties and durability (on occasion bettering traditional Portland cement performance). Moreover, development of these cements may contribute to mitigating CO2 emissions, since the base material is an industrial by-product. The present study was conducted to determine the effect of the composition of the initial materials (SiO2/Al2O3 and Na2O/Al2O3 ratios) on the mechanical properties, nature and composition of the reaction products. The results obtained indicate that there is no linear relationship between these ratios and mechanical strength, but rather a series of optimal values above and below which strength declines. In the specific case of the ratios studied in the present paper, these values were: SiO2/Al2O3= 4.0 and Na2O/Al2O3= 1.0 (molar ratios).


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(1) Glukhovskiy, V.D., Soil silicates. Gosstroy publsh, Kiev (1959). (in Russian)

(2) Glukhovskiy, V.D., Soil-Silicate Articles and Constructions. Kyiv, Budivelnik publish (1967). (in Ukrainian)

(3) Krivenko, P.V., Alkaline Cements. Proceed. First Intern. Conf. "Alkaline cements and Concretes". Kiev, Vipol publish, pp. 11-129 (1994).

(4) Krivenko, P.V., Alkaline Cements: Terminology, Classification, Aspects of Durability. Proceed. Tenth Intern. Congress on the Chemistry of Cement, Göteborg, Sweden, p. 4iv046-4iv050 (1997).

(5) Davidovits, J. (ed.), Proceed. First European Conf. On Soft Mineralurgy "Geopolymer'88", Compiegne (1988).

(6) Palomo, A., Grutzeck M.W., Blanco M.T., “Alkali-activated fly ashes - A cement for the future” Cement and Concrete Research, 29 (8), pp.1323-1329 (1999). doi:10.1016/S0008-8846(98)00243-9

(7) Hua Xu and Jannie S.J. van Deventer, “Effect of Source Materials on geopolymerization”. Ind. Eng. Chem. Res. Vol. 42, pp.1698-1706 (2003). doi:10.1021/ie0206958

(8) Rostovskaya, G., Illyin, V., and Brodko, O., The investigation of Service Properties of the Slag Alkaline Concretes. Proceed. Intern. Symposium "Non-traditional Cement&Concrete", Brno, pp.510-523 (2002).

(9) Chirkova, V.V., Materials Based on Glass-Like Calcium-Free Aluminosilicates and Sodium Compounds. PhD Thesis, Kiev (1974). (in Russian)

(10) Krivenko, P.V., and Skurchinskaya, J.V., Fly Ash Containing Geocements. Proceed. Intern. Conf. on the Utilization of Fly Ash and other Coal Combustion By-Products, Shanghai, pp 64-1 – 64-7 (1991).

(11) Krivenko, P.V., Fly Ash – Alkali Cements and Concretes. Proceed. 4th CANMET-ACI Intern. Conf. on Fly Ash, Silica Fume, Slag and Natural Pozzolans in Concrete, Istanbul pp. 721-734 (1992).

(12) Krivenko, P.V., and Kovalchuk, G.Yu., Fly Ash Based Zeolite Cements. Innovations and Developments in Concrete Materials and Construction: Proceed. Intern. Conf. “Challenges of Concrete Construction”, Dundee, pp. 123-132 (2002).

(13) Krivenko, P.V., and Kovalchuk, G.Yu., Heat-Resistant Fly Ash Based Geocements. Proceed. Intern. Conf. “Geopolymers 2002”, Melbourne (2002).

(14) Kovalchuk, G.Yu., Heat Resistant Gas Concrete Based on Alkaline Aluminosilicate Binder. PhD Thesis, Kyiv (2002). (in Ukrainian)

(15) Palomo, A., Alonso, S., Fernández-Jiménez, A., Sobrados, I., Sanz, J., “Alkaline Activation of Fly Ashes: NMR Study of the Reaction Products”, J. Am. Ceram. Soc., 87 (6), pp.1141-1145 (2004).

(16) Fernández-Jiménez, A., Palomo, A. and López-Hombrados, C., “Some engineering properties of alkali activated fly ash concrete” ACI Materials Journal 103 (2) pp. 106-112 (2006).

(17) Fernández-Jiménez, A., Palomo, A., Criado, M., “Alkali activated fly ash binders. A. comparative study between sodium and potassium activators”. Mater. Construcc. 56, nº 281, pp. 51-65 (2006).

(18) Duxson, P., Fernández-Jiménez, A., Provis, J.L., Lukey, G.C., Palomo, A., van Deventer J.S.J. “Geopolymer technology: The current state of the art. J. Materials Science (Aceptado en prensa 2007).

(19) Duxson, P., Provis, J.L., Lukey, G.C., Mallicoat, S.W., Kriven W.M., van Deventer J.S.J., “Understanding the relationship between geopolymer composition, microstructure and mechanical properties” Colloids and surfaces A, 269, pp. 47-58 (2005). doi:10.1016/j.colsurfa.2005.06.060

(20) Buchwald, A., Schulz, M., “Alkali-activated binders by use of industrial by-products” Cement and Concrete Research, 35 (5), pp. 968-973 (2005). doi:10.1016/j.cemconres.2004.06.019 (21) Skvara, F., Slosar, J., Bohunek, J., and Markova, A., Alkali-Aktivated Fly Ash Geopolymeric Materials. Proceed. 11th Intern. Congress on the Chemistry of Cement, Durban pp. 1341-1350 (2003).

(22) Van Jaarsveld, J.G.S., Van Deventer, J.S.J. “Effect of the Alkali Metal Activator on the Properties of Fly Ash Based Geopolymers”. Ind. Eng. Chem. Res. 38, nº10, pp. 3932-3941 (1999). doi:10.1021/ie980804b

(23) Fernández-Jiménez, A., Palomo, A., “Composition and microstructure of alkali activated fly ash binder: Effect of the activator”, Cem. Con. Res., 35, pp.1984-1992 (2005). doi:10.1016/j.cemconres.2005.03.003

(24) Kovalchuk, G., Fernández-Jiménez, A., Palomo, A., “Alkali-activated fly ash: Effect of thermal curing conditions on mechanical and microstructural development-Part II” Fuel, 86, pp. 315-322 (2007). doi:10.1016/j.fuel.2006.07.010

(25) Fernández-Jiménez, A., García-Lodeiro, I., and Palomo, A., “Durable characteristics of alkali activated fly ashes” J. Materials Science (Aceptado, en prensa 2007)

(26) Caijun Shi, Fernández-Jiménez A., “Stabilization/Solidification of Hazardous and Radioactive Wastes With Alkali-Activated Cements” J. Hazardous Materials. 11, pp. 1656-1663 (2006). doi:10.1016/j.jhazmat.2006.05.008

(27) Criado M., Palomo A., Fernández-Jiménez A., “Alkali activation of fly ashes. Part 1: Effect of curing conditions on the carbonation of the reaction products” FUEL, 84, pp. 2048-2054 (2005). doi:10.1016/j.fuel.2005.03.030

(28) Van Jaarsveld, J.G.S., van Deventer J.S.J. and Lorenzen, L, “The potential use of geopolymeric materials to immobilise toxic metals, Part I. theory and applications”, Minerals Engineering, 10, 659 (1996). doi:10.1016/S0892-6875(97)00046-0

(29) Fernández-Jimenez A., de la Torre A.G., Palomo A., López-Olmo G., Alonso M.M. and Aranda M.A.G., Quantitative determination of phases in alkaline activation of fly ashes. Part II the degree of reaction FUEL 85, pp. 1960-1969 (2006). doi:10.1016/j.fuel.2006.04.006

(30) Fernández-Jiménez, A., Palomo, A., “Characterisation of fly ashes. Potential reactivity as alkaline cements”, Fuel, 82, pp. 2259-2265 (2003). doi:10.1016/S0016-2361(03)00194-7

(31) Fernández-Jiménez, A., de la Torre, A.G., Palomo, A., López-Olmo, G., Alonso, M.M., Aranda, M.A.G., “Quantitative determination of phases in the alkali activation of fly ash. Part I. Potential ash reactivity”, Fuel, 85, pp. 625-634 (2006). doi:10.1016/j.fuel.2005.08.014

(32) Fernández-Jiménez, A., Palomo, A., Sobrados, I., Sanz, J. “The role played by the reactive alumina content in the alkaline activation of fly ashes”, Microp. Mesop. Mat. 91, pp. 111-119 (2006). doi:10.1016/j.micromeso.2005.11.015

(33) Querol, X., Alastuey, A., Lopez-Soler, A., Plana, F., Andres, J.M., Juan, R. Ferrer, P. and Ruiz, C.R., “A fast method for recycling fly ash: microwave-assisted zeolite synthesis”, Environmental Science and Technology, 31, pp. 2527– 2533 (1997). doi:10.1021/es960937t

(34) Criado M., Fernández-Jiménez A., de la Torre A.G., Aranda M.A.G. and Palomo A. “An XRD study of the effect of the SiO2/Na2O ratio on the alkali activation of fly ash” Cement and Concrete Research (in press)

(35) Barrer, R.M., Hydrothermal Chemistry of Zeolites. Academic Press, London, 1982.

(36) Breck D.W. “Zeolita Molecular Sieves”, Ed. Krieger (1974), Florida, EEUU. (37) Fernández-Jiménez, A., Palomo, A., “Mid-infrared spectroscopic studies of alkali-activated fly ash structure”, Micro. and Mesoporous Mat., 86, pp. 207-214 (2005). doi:10.1016/j.micromeso.2005.05.057

(38) Criado, M., Fernández-Jiménez, A. and Palomo, A., “Alkali activation of fly ash. Effect of the SiO2/Na2O ratio. Part I. FTIR study” Microporous and mesoporous materials (in press).

(39) Mozgawa, W., Sitarz, M., Rokita, M., “Spectroscopic studies of different aluminosilicate structures” J. Molecular Structure, 511-512, pp. 251-257 (1999). doi:10.1016/S0022-2860(99)00165-9

(40) Palomo A., Fernández-Jiménez A., and Criado M., “Geopolymers: one only chemical basis, some different microstructures” Mater Construcc, Vol. 54, nº 275, pp. 77-91 (2004)

(41) Criado, M., Fernández-Jiménez, A., Palomo, A., Sobrados, I., and Sanz, J.,“Alkali activation of fly ash. Effect of the SiO2/Na2O ratio. Part II. 29Si NMR study” Microporous and mesoporous materials (enviado).

(42) Lee, W.K.W., and Van Deventer, J.S.J., “Structural reorganization of class F fly ash in alkaline silicate solutios”, Colloids and Surfaces A: Physicochem Eng. Aspects. 211, pp. 49-66 (2002). doi:10.1016/S0927-7757(02)00237-6




How to Cite

Kovalchuk, G., Fernández-Jiménez, A., & Palomo, A. (2008). Alkali-activated fly ash. Relationship between mechanical strength gains and initial ash chemistry. Materiales De Construcción, 58(291), 35–52.



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