Characterization of differing forms of unburned carbon present in fly ash separated by density gradient centrifugation

摘要: Abstract It is generally known that the ASTM LOI specification not sufficient to identify suitability of a fly ash for cement industry, since this criterion only gives an approximation carbon content sample and in many instances provides poor correlation with capacity adsorb air-entrainment admixtures (AEAs). Petrographic examinations have shown unburned visually uniform three microscopically distinct types been identified: inertinite, isotropic coke anisotropic coke. Concentrates these generated from two high-carbon-content samples using technique density gradient centrifugation (DGC). The work reported here represents first characterization bulk properties types, where highest DGC purity fractions were extensively analyzed by several analytical techniques, including elemental surface area analyses. like forms isolated ashes appears be quite similar, regardless source ash. H/C atomic ratios are ∼0.03–0.02, indicating high degree condensation. areas relatively low (10–60 m 2  g −1 ), most pores mesopore range (2–50 nm width). For both series samples, was found increase linearly increasing particle density. On basis distinctive physical chemical (density, nitrogen oxygen concentrations, as well volume) it anticipated each type will specific adsorption behavior AEAs.