The leachability of heavy metals in hardened fly ash cement and cement-solidified fly ash

The enhancement effect of pre-reduction using zero-valent iron on the solidification of chromite ore processing residue by blast furnace slag and calcium hydroxide

“…One promising technology is the stabilization/solidification (S/S) (Dermatas and Meng, 2003;Dalmacija et al, 2011) of solid wastes by mixing the waste with a binder to reduce the leachability of the contaminants and to convert the hazardous waste into an environmentally acceptable form of waste for land disposal or as recyclable construction material. Cement-based, cement/fly ash-based and lime/fly ash-based S/S technologies are the generic S/S processes, and solidification of Cr in cementitious matrices has been studied by many researchers (Dechesne and Laforest, 2004;Yu et al, 2005;Zhang et al, 2009;Bulut et al, 2009;Shi and Kan, 2009). However, it has been reported that some metals such as chromium (VI), arsenic (III) and mercury are not suitable for use with this type of binding material since they do not form highly insoluble hydroxides (Mulligan et al, 2001).…”

Earth Masonry Unit: Sustainable Cmu Alternative

“…The composition of fly ash, one of the most plentiful and widely-used OPC substitutes, varies widely with fuel source, and has been shown to contain such highly toxic elements such as arsenic, beryllium, cadmium, chromium and lead, among others, along with dioxins and polycyclic aromatic hydrocarbons compounds in concentrations that can be up to several percent of the total material [7]. Questions remain as to whether the hydration reaction of fly ash and cement is capable of sufficiently immobilizing the toxic elements in fly ash and leaching of heavy metals, which is of special concern where concrete comes into contact with water [8,9].…”

“…Questions remain as to whether the hydration reaction of fly ash and cement is capable of sufficiently immobilizing the toxic elements in fly ash and leaching of heavy metals, which is of special concern where concrete comes into contact with water [8,9]. Past experiences with lead paint, asbestos and arsenic-treated wood should prevent the widespread use of a product until the impacts on human health [7] are fully understood, and additional research is needed to assure the nontoxicity of concrete incorporating significant amounts of fly ash and other SCMs over the life of these materials, particularly where residential construction is concerned.…”

Preliminary study on the concentration of some heavy metals around a proposed cement factory in Kogi State Nigeria

“…Chromium, Cd and Co has also been found to be leached from cement (Yu et al, 2005;Zhang et al, 2009;Bobrowski et al, 1997;Yang et al, 2009;Achternbosch et al, 2003). Some methods have been developed to stabilize some of these heavy metals in sewage sludge (Yi-Chin and Kung-Cheh, 2004;Quanyuan et al, 2009;Peysson et al, 2005;Juu-En et al, 1999;Paone, 2008;Vespa et al, 2006;Ahn et al, 2006;Liang et al, 2008).…”