Enhancement of selectivity toward ettringite during hydrothermal processes on fluidized bed combustion wastes for the manufacture of preformed building components. Issue 123 (26th November 2015)

• Record Type: Journal Article
• Authors: Telesca, Antonio; Marroccoli, Milena; Montagnaro, Fabio; Tomasulo, Michele; Valenti, Gian Lorenzo
• Is Part Of: RSC advances. Volume 5:Issue 123(2015)
• Page Start: 101887
• Page End: 101893
• Publication Date: 2015-11-26
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c5ra15536c
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : This advance is concerned with reactivity improvements of hydrating systems, based on fluidized bed combustion wastes, toward ettringite. Abstract : Due to its lime, alumina and calcium sulfate contents, fluidized bed combustion (FBC) waste is worthy of consideration as a raw material for the hydrothermal synthesis of building elements based on ettringite (6CaO·Al2 O3 ·3SO3 ·32H2 O). Two FBC waste samples (a fly and a bottom ash) were hydrated, alone and in a mixture, at temperatures between 40° and 85 °C for curing times ranging from 2 hours to 7 days, and were submitted to X-ray diffraction and differential thermal-thermogravimetric analyses. It has been found that: (a) the FBC fly ash could be hydrated alone, due to its satisfactory ettringite-generating ability; (b) the FBC bottom ash needed to be used together with other raw materials; (c) progressively better results were obtained by adding (i) FBC fly ash to FBC bottom ash (to give a blend with a 60 : 40 mass ratio), (ii) anodization mud (a by-product of anodized aluminum manufacture, acting as an additional source of alumina and calcium sulfate) in a measure of 10% by mass to the fly-bottom ash blend, (iii) anodization mud (20% by mass) to the FBC bottom ash. Moreover, compressive strength measurements were carried out, according to the EN 196-1 Standard for cements, on the hydrated systems showing the two largest ettringite concentrations, and a maximum value of about 6 MPa was reached at 70 °C and 16 hours of curing. The data obtained in this investigation were consistent with an industrial prefabrication of building components.