Physical Gel Versus Pozzolanic Reactions for Agglomerating of Fine Particulates

Inorganic agglomerates of concentrated iron ores are typically made using a sodium bentonite as a binding agent. This paper examines the effects of adding corn starch and fly ash to bentonite for making concentrated iron ore agglomerates. The use of a mixture of bentonite and fly ash revealed a distinctly different binding mechanism than the use of a mixture of corn starch and bentonite. Fly ash bentonite mixtures showed pozzolanic activity as the principle binding mechanism as the concentration of fly ash in the mixture approached 100%. At lower concentrations of fly ash in the mixture, the competing mechanisms of bentonite and fly ash diminished the strength of the agglomerates. Corn starch – bentonite mixtures showed physical gelling and expulsion of moisture as the principle binding mechanism as the concentration of corn starch in the mixture approached 100%. Examination of these binding mechanisms and their roles in agglomeration will be discussed.