Role of Fly Ash Pozzolanic Reactions in Controlling Fluoride Release from Phosphogypsum
Publication: Journal of Materials in Civil Engineering
Volume 25, Issue 8
Abstract
Phosphogypsum is added to building materials to accelerate fly ash pozzolanic reaction and contributes to early strength development of concrete. The release of unacceptable fluoride levels by phoshogypsum on contact with water is a major impediment in its usage to manufacture building products because excess fluoride consumption causes dental and skeletal fluorosis. This paper examines the efficacy of fly ash pozzolanic reactions in controlling fluoride release by phosphogypsum. Fly ash (FA), sand (S), lime (L), and phosphogypsum (G) (FA-S-L-G) slurries are cured for various periods, and the fluoride released by the mix is monitored as a function of time. A substantial reduction in fluoride release was observed and is attributed to entrapment of phosphogypsum particles in a cementious matrix formed by fly ash-lime pozzolanic reactions coupled with consumption of fluoride in formation of insoluble compounds. The compressive strength developed by compacted FA-S-L-G specimens with time was observed to be a three-stage process; maximum strength mobilization occurred during 14 and 28 days of curing at room temperature. Exposure of the compacted FA-S-L-G specimens to acidic and alkaline environments for 9 days did not impact their compressive strengths.
Get full access to this article
View all available purchase options and get full access to this article.
References
Aimin, X., and Sarkar, S. L. (1991). “Microstructural study of gypsum activated fly ash hydration in cement paste.” Cem. Concr. Res., 21(6), 1137–1147.
Asha, K. (2012). “Activation of fly ash-lime reactions by curing at elevated temperature and by addition of phosphogypsum.” Ph.D. dissertation, Indian Institute of Science, Bangalore, India.
ASTM. (1985). “Standard test method for shake extraction of solid waste with water.” D3987, West Conshohocken, PA.
ASTM. (2008). “Standard specification for coal fly ash and raw or calcined natural pozzolan for use in concrete.” C618, West Conshohocken, PA.
Azam, S. A., Abduljauwad, B. S. N., Naser, A., Al-Shayea, B., and Al-Amoudi, O. S. B. (1998). “Expansive characteristics of gypsiferrous/anhydritic soil formations.” Eng. Geol., 51(2), 89–107.
Basumajumdar, A., Das, A. K., Bandyopadyay, N., and Maitra, S. (2005). “Some studies on the reaction between fly ash and lime.” Bull. Mater. Sci., 28(2), 131–136.
Bureau of Indian Standards. (1977). “Determination of total soluble solids.” IS 2720, New Delhi, India.
Bureau of Indian Standards. (1987). “Determination of pH value.” IS 2720, New Delhi, India.
Bureau of Indian Standards. (1991). “Drinking water—Specification.” IS 10500, New Delhi, India.
Fawell, J., Bailey, K., Chilton, J., Dahi, E., Fewtrell, L., and Magara, Y. (2006). “Fluoride in drinking water.” World Health Organization Rep., International Water Association, London.
Garg, M., Singh, M., and Kumar, R. (1996). “Some aspects of the durability of a phosphogypsum-lime-fly ash binder.” Constr. Build. Mater., 10(4), 273–279.
Karni, J., and Karni, E. (1995). “Gypsum in construction.” Mater. Struct., 28(2), 92–100.
Kumar, S. (2000). “Fly ash-lime-phosphogypsum cementitous binder: A new trend in bricks.” Mater. Struct., 33(1), 59–64.
Lopez, F. A., Gazquez, M., Alguacil, F. J., Bolivar, J. P., Garcia-Diaz, I., and Lopez-Cotob, I. (2011). “Microencapsulation of phosphogypsum into a sulfur polymer matrix: Physico-chemical and radiological characterization.” J. Hazard. Mater., 192(1), 234–245.
Motalane, M. P., and Strydom, C. A. (2004). “Potential groundwater contamination by fluoride from two South African phosphogypsum.” S. Afr. Water Res. Commission, 30, 465–468.
Narasaraju, T. S. B., and Phebe, D. E. (1996). “Some physico-chemical aspects of hydroxylapatite.” J. Mater. Sci., 31(1), 1–21.
Pandian, N. S., Rajasekhar, C., and Sridharan, A. (1998). “Studies on the specific gravity of some Indian coal ashes.” J. Test. Eval., 26(3), 177–186.
Poon, C. S., Kou, S. C., Lam, L., and Lin, Z. S. (2001). “Activation of fly ash/cement systems using calcium sulfate anhydrite ().” Cem. Concr. Res., 31(6), 873–881.
Rao, S. M., Reddy, B. V. V., Raju, G. C., Lakshmikanth, S., and Ambika, N. S. (2009). “Chemical stabilization of lead contaminated gypsum sludge.” Int. J. Geotech. Eng., 3(1), 109–116.
Reddy, B. V. V., Lal, R., and Rao, K. S. N. (2007). “Optimum soil grading for the soil-cement blocks.” J. Mater. Civ. Eng., 19(2), 139–148.
Rutherford, P. M., Dudas, M. J., and Samek, R. A. (1994). “Environmental impacts of phosphogypsum.” Sci. Total Environ., 149(1–2), 1–38.
Sanders, J. F., Keener, T. C., and Wang, J. (1995). “Hydrated fly ash/hydrated lime slurries for removal in spray dryer absorbers.” Ind. Eng. Chem. Res., 34(1), 302–307.
Shen, W., Zhou, M., and Zhao, Q. (2007). “Study on lime-fly ash-phosphogypsum binder.” Constr. Build. Mater., 21(7), 1480–1485.
Singh, M., Garg, M., and Rehsi, S. S. (1993). “Purifying phosphogypsum for cement manufacture.” Constr. Build. Mater., 7(1), 3–7.
Tayibi, H., Choura, M., Lopez, A. F., Alguacil, F. J., and Delgado, A. L. (2009). “Environmental impact and management of phosphogypsum.” J. Environ. Manage., 90(8), 2377–2386.
Todd, D. K. (1980). Groundwater hydrology, 2nd Ed., Wiley, New York.
Urhan, S. (1987). “Alkali silica and pozzolanic reactions in concrete. Part 1: Interpretation of published results and an hypothesis concerning the mechanism.” Cem. Concr. Res., 17(1), 141–152.
USEPA. (1992). “Toxicity characteristic leaching procedure, method 1311 in test methods for valuating solid waste (SW-846).” TCLP 1311, Office of Solid Waste, Economic Methods and Risk Analysis, Washington, DC.
Ward, R. C., and French, D. (2005). “Relation between coal and fly ash mineralogy based on quantitative XRD methods.” Proc., World of Coal Ash Conf. (WOCA), University of Kentucky, Centre for Applied Energy Research, Kentucky, 1–14.
Information & Authors
Information
Published In
Journal of Materials in Civil Engineering
Volume 25 • Issue 8 • August 2013
Pages: 999 - 1005
Copyright
© 2013 American Society of Civil Engineers.
History
Received: Dec 9, 2011
Accepted: Aug 9, 2012
Published online: Jul 15, 2013
Published in print: Aug 1, 2013
Discussion open until: Dec 15, 2013
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.