Study of Geopolymeric Binders of Fly Ash/Metakaolin Mixtures Cured at Room Temperature

Abstract:

Geopolymerization is a chemical process in which aluminosilicate materials are precursors to obtain binders that have a low environmental impact. Fly ash has been used as a precursor for the development of these binders. However, thermal curing is needed to accelerate the polycondensation of aluminosilicate, which limits the application of this new binder in the construction industry. Thus, the objective of this study was to evaluate the feasibility to obtain such binders with good mechanical properties when cured at room temperature. The precursor material consisted of different mixtures of fly ash and metakaolin that were activated using combined sodium hydroxide and sodium silicate alkaline solutions. The effect on the compressive strength of different proportions of the alkaline solutions was studied. Compressive strengths of about 40 MPa were achieved at 91 days for the samples containing 70% fly ash and 30% metakaolin, activated using an alkaline solution of 50% sodium hydroxide and 50% sodium silicate. X-ray diffraction analysis showed the formation of natrite in geopolymeric samples, as well as the presence of crystalline compounds, such as quartz, mullite and hematite, in fly ash and metakaoline. Scanning electron microscopy analysis showed that in geopolymeric mixtures with higher compressive strength dissolution of fly ash and metakaolin particles occurred almost completely and that aluminosilicate dense gel has been formed extensively.

• Periodical: Key Engineering Materials (Volume 600)
• Pages: 338-344
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.600.338
• Online since: March 2014
• Authors: Alexandre Silva de Vargas*, Ruby M. de Gutierrez, João Castro-Gomes
• Keywords: Compressive Strength, Curing Temperature, Fly Ash (FA), Geopolymer, Metakaolin (MK)

References

[1] A. Palomo, M. W. Grutzeck, M. T. Blanco, Alkali-activated fly ashes, A cement for the future, Cement and Concrete Research. 29 (1999) 1323-1329.

DOI: 10.1016/s0008-8846(98)00243-9

[2] C. Li, H. Sun, L. Li, A review: the comparison between alkali-activated slag (Si + Ca) and metakaolin (Si + Al) cements, Cement and Concrete Research. 40 (2010) 1341-1349.

DOI: 10.1016/j.cemconres.2010.03.020

[3] J. P. Gleize, M. Cyr, g. Escadeillas, Effects of metakaolin on autogenous shrinkage of cement pastes, Cement & Concrete Composites. 29 (2007) 80-87.

DOI: 10.1016/j.cemconcomp.2006.09.005

[4] A. Fernández-Jiménez, M. Monzó, M. Vicent, A. Barba, A. Palomo, Alkaline activation of metakaolin-fly ash mixtures: Obtain of Zeoceramics and Zeocements. Microporous and Mesoporous Materials 108 (2008) 41-49.

DOI: 10.1016/j.micromeso.2007.03.024

[5] J. G. S. Van Jaarsveld, J.S.J. van Deventer, L. Lorenzen, The potential use of geopolymeric materials to immobilize toxic metals: Part I, Theoria and Applications, Minerals Engineering. 10 (1997) 659-667.

DOI: 10.1016/s0892-6875(97)00046-0

[6] A. S. de Vargas. Alkali-activated fly ash for the production of special cements. University Federal Of Rio Grande do Sul, Doctoral Thesis, Porto Alegre, 2006, pp.1-169 (in Portuguese).

DOI: 10.29289/259453942018v28s1059

[7] American Society For Testing and Materials (ASTM). Standard Specification for Coal Fly abd Raw or Calcined Original Pozzolan for Use as a Mineral Admixture in Concrete,. ASTM C618/98, in: Annual Book of ASTM, 04. 02, Philadelphia, (1998).

[8] C. Shi, Early microstructure development of activated lime-fly ash pastes, Cement and Concrete Research 26 (1996) 1351-1359.

DOI: 10.1016/0008-8846(96)00123-8

[9] J. Davidovits, J. L Sawyer, U. S. Patent 4, 509, 985. (1985).

[10] D. Hardjito, B. V. Rangan, Development and properties of low-calcium fly ash-based geopolymer concrete, in: Research Report GC 1. Faculty of Engineering Curtim University of Technology, Perth, 2005, pp.1-94.

[11] T. Bakharev, Geopolymeric materials prepared using Class F fly ash elevated temperature curing, Cement and Concrete Research, 35 (2005) 1224-32.

DOI: 10.1016/j.cemconres.2004.06.031

[12] A. Fernández-Jiménez, M. Monzo, M. Vicent, A. Barba, A. Palomo, Alkaline activation of metakaolin-fly ash mixtures: Obtain of Zeoceramics and Zeocements, Microporous and mesoporous materials 108 (2008) 41-49.

DOI: 10.1016/j.micromeso.2007.03.024