Recycling of low-silicon iron tailings in the production of lightweight aggregates

This paper reports the result of the investigation on manufacturing lightweight aggregate by the mixtures of the low-silicon iron tailings, fly ash and powdery quartz sand. The raw materials were characterized by chemical compositions, X-ray diffraction and particle size. The investigation was performed in a laboratory scale to assess the effects of the composition of the mixtures and the sintering conditions on the properties of the artificial lightweight aggregates. The effects of the composition of the mixtures and sintering temperatures on the bloating index, loose bulk density, apparent density, water absorption and compressive strength were determined. All the mixtures studied in the paper presented a bloating potential at high temperatures. The bloating index of all the samples is greater than 1, so all types of aggregates were expanded aggregates. The products obtained were lightweight aggregates. The microstructure and the phase composition of the lightweight aggregates were analyzed by scanning.electron microscopy (SEM) and X-ray diffraction (XRD). The main mineral phases of the products were hematite, quartz and anorthite, which were principally responsible for the mechanical strength of the aggregates. The analysis of microstructures with SEM revealed a vitrified matrix and an extended formation of isolated and closed pores.