Engineering and environmental properties of thermally treated mixtures containing MSWI fly ash and low-cost additives

Microstructure and mineralogy of lightweight aggregates produced from washing aggregate sludge, fly ash and used motor oil

“…lb and 3c). These phases have also been identified in sintered products made from incinerator bottom and fly ash [33][34][35]. Pyroxenes are neo-formed phases, since the raw materials (fly ash and washing aggregate sludge) did not con tain them.…”

“…Wollastonite could be formed by the reaction of cal cite and quartz, accompanied by CO2 release, at temperatures high er than 600-700 °C [34]. This neo-formation mechanism has been reported for raw materials containing quartz and calcite and lack ing clay minerals, such as illite [33][34][35]. In this study, the washing aggregate sludge is also composed of clay minerals; therefore, an alternative neo-formation mechanism could exist, such as reaction of the clay minerals with the calcium resulting from the decarbon ation of calcite.…”

Leaching behaviour of a glassy slag and derived glass ceramics from arc plasma vitrification of hospital wastes

“…The basicity of PG glass calculated from its chemical composition (Table 1) is 0.51, whereas by considering a stoechiometric composition, the basicity value for the crystallized phases in PGC samples are 1 for wollastonite (CaO·SiO 2 ) and akermanite (2CaO·MgO·2SiO 2 ) and 2 for gehlenite (2CaO·Al 2 O 3 ·SiO 2 ). Therefore, the fraction of metals available for leaching is reduced as results of the lower basicity of the glassy phase, which leads to chemical fixation mechanism within the silicate structure taking place during glass crystallization, as reported by previous studies 27,28 . In all cases, the concentration of every leached metal is below the limits allowed by the U.S. Environmental Protection Agency (US EPA).…”

Microstructure and mineralogy of lightweight aggregates manufactured from mining and industrial wastes

“…Instead of gehlenite, pyroxene group minerals are detected (such as ferroan diopside (Ca(Mg,Fe)Si 2 0 6 ), Table 4 ) in W75S25-1150-15. Pyroxenes have also been identified in LWAs and glass-ceramics prepared from different types of wastes [4,31,32]. They can be regarded as neo-formed minerals, since the raw materials (Wand SS) do not contain pyroxenes.…”

“…A possible neo-formation mechanism would be substitutions of the Ca in the original structure of wollastonite (CaSi0 3 ) for Mg and Fe. Wollastonite was formed by the reaction of calcite and quartz, accompanied by CO 2 release, at temperatures higher than 600-700°C [31] . This neo-formation mechanism has been reported for raw materials containing quartz and calcite and lacking clay minerals, such as illite.…”