Abstract
Blended fly ash/blast-furnace slag geopolymers are focused on due to their excellent mechanical and chemical resistant properties. We investigated the effect of slag partial substitution for fly ash on the efflorescence of the resulting geopolymers. The efflorescence of geopolymer binders was inspected and evaluated through leaching tests. The efflorescence deposits on surface of the geopolymer binders were analyzed using XRD and SEM-EDS. The results showed that sodium and calcium cations leached from geopolymer binders reacted with the atmospheric CO2 and formed the crystal deposits, gaylussite and calcite, in the forms of granular and angular crystal particles. The slag addition led to a refinement of the pore structure of fly ash-based geopolymers, but an increment in the concentration of alkali leaching. The crystal deposits gradually developed in the pore volume of the binders, and finally exceeded the capacity of pore volume. The extent of efflorescence on the surface of specimens increased with the slag substitution. The visible efflorescence is therefore a result of available alkalis and pore sizes and volumes. Higher concentration of available alkalis and smaller pores (and volume) will lead to more intensive efflorescence.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Davidovits J. Geopolymers[J]. Journal of Thermal Analysis and Calorimetry, 1991, 37: 1633–1656
Duxson P, Fernández-Jiménez A, Provis JL, et al. van Deventer. Geopolymer Technology: The Current State of the Art[J]. Journal of Materials Science, 2007, 42: 2917–2933
Davidovit J. Geopolymer Chemistry and Applications[M]. second ed. France: Institut Géopolymére, 2008
McLellan BC, Williams RP, Lay J, et al. Costs and Carbon Emissions for Geopolymer Pastes in Comparison to Ordinary Portland Cement[J]. Journal of Cleaner Production, 2001, 19: 1080–1090
Zhang Z, Provis JL, Reid A, et al. Geopolymer Foam Concrete: An Emerging Material for Sustainable Construction[J]. Construction and Building Materials, 2014, 56: 113–127
Duxson P, Lukey GC, Separovic F, et al. Effect of Alkali Cations on Aluminum Incorporation in Geopolymeric Gels[J]. Industrial and Engineering Chemistry Research, 2005, 44: 832–839
Lloyd RR, Provis JL, van Deventer JSJ. Pore Solution Composition and Alkali Diffusion in Inorganic Polymer Cement[J]. Cement and Concrete Research., 2010, 40: 1386–1392
Škvára F, Šmilauer V, Hlavácek P, et al. A Weak Alkali Bond in (N, K)-A-S-H Gels: Evidence from Leaching and Modeling[J]. Ceramicssilikaty., 2012, 56: 374–382
Škvára F, Kopecký L, Myšková L, et al. Aluminosilicate Polymersinfluence of Elevated Temperatures, Efflorescence[J]. Ceramicssilikaty, 2009, 53: 195–204
Kani EN, Allahverdi A, Provis JL. Efflorescence Control in Geopolymer Binders Based Natural Pozzolan[J]. Cement and Concrete Composites, 2012, 34: 25–33
Szklorzová H, Bílek V. Influence of Alkali Ions in the Activator on the Performance of Alkali-activated Mortars[C]. 3rd International Symposium on Non-traditional Cement and Concrete. Brno: Czech Republic, 2008
Duxson P, Provis JL, Lukey GC, et al. 39K NMR of Free Potassium in Gopolymers[J]. Industrial and Engineering Chemistry Research, 2006, 45: 9208–9210
Puligilla S, Mondal P. Role of Slag in Microstructural Development and Hardening of Fly ash-slag Geopolymer[J]. Cement and Concrete Research, 2013, 43: 70–80
Provis JL, Myers RJ, White CE, et al. X-ray Microtomography Shows Pore Structure and Tortuosity in Alkali-activated Binders[J]. Cement and Concrete Research, 2012, 42: 855–864
Yang T, Yao X, Zhang Z, et al. Mechanical Property and Structure of Alkali-activated Fly Ash and Slag Blends[J]. Journal of Sustainable Cement-based Materials, 2012, 1: 167–178
Ma Y, He J, Ye G. The Pore Structure and Permeability of Alkali Activated Fly Ash[J]. Fuel, 2013, 104: 771–780
Yang T, Yao X, Zhang Z. Geopolymer Prepared with High-magnesium Nickel Slag: Characterization of Properties and Microstructure[J]. Construction and Building Materials, 2014, 59: 188–194
Ismail I, Bernal SA, Provis JL, et al. Modification of Phase Evolution in Alkali-activated Blast Furnace Slag by the Incorporation of Fly Ash[J]. Cement and Concrete Composites, 2014, 45: 125–135
Bernal SA, Provis JL, Walkley B, et al. Gel Nanostructure in Alkaliactivated Binders Based on Slag and Fly Ash, and Effects of Accelerated Carbonation[J]. Cement and Concrete Research, 2013, 53: 127–144
Author information
Authors and Affiliations
Corresponding author
Additional information
Funded by the Jiangsu Higher Education Institutions for a project PAPD (Priority Academic Program Development), Program for Changjiang Scholars and Innovative Research Team in University (PCSIRT), (No.IRT1146) and Graduate Education Innovation Project in Jiangsu Province (No.CXLX13_409). The work by Zhang is supported by University of Southern Queensland and an ARC-linkage project.
Rights and permissions
About this article
Cite this article
Yao, X., Yang, T. & Zhang, Z. Fly ash-based geopolymers: Effect of slag addition on efflorescence. J. Wuhan Univ. Technol.-Mat. Sci. Edit. 31, 689–694 (2016). https://doi.org/10.1007/s11595-016-1430-8
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11595-016-1430-8