Role of Fly Ash Pozzolanic Reactions in Controlling Fluoride Release from Phosphogypsum

Rao, Sudhakar M and Asha, K (2013) Role of Fly Ash Pozzolanic Reactions in Controlling Fluoride Release from Phosphogypsum. In: JOURNAL OF MATERIALS IN CIVIL ENGINEERING, 25 (8). pp. 999-1005.

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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 28days 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. (C) 2013 American Society of Civil Engineers.

Item Type:	Journal Article
Publication:	JOURNAL OF MATERIALS IN CIVIL ENGINEERING
Publisher:	ASCE-AMER SOC CIVIL ENGINEERS
Additional Information:	Copyright of this article is belongs to ASCE-AMER SOC CIVIL ENGINEERS
Keywords:	Fly ash; Solidification; Compressive strength; Concrete admixtures; Fly ash; Fluoride; Phosphogypsum; Pozzolanic reaction
Department/Centre:	Division of Mechanical Sciences > Centre for Sustainable Technologies (formerly ASTRA) Division of Mechanical Sciences > Civil Engineering
Date Deposited:	03 Sep 2013 10:28
Last Modified:	03 Sep 2013 10:30
URI:	http://eprints.iisc.ac.in/id/eprint/47033

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