Characterization of chemical accelerators for sustainable recycling of fresh electric-arc furnace dust in cement pastes

Abstract

A comprehensive investigation focusing on the effect of fresh EAFD on the setting of cement pastes was conducted. A new approach of using accelerators to counteract the extended retardation associated with using fresh EAFD was investigated. Two chloride-free chemical accelerators (CFCA), namely, calcium nitrite (CN) and calcium formate (CF) were used and their performance was benchmarked against calcium chloride (CC). Temperature profile was used for validating setting times by Vicat needle apparatus. Homogenization of fresh EAFD from different furnaces resulting in an average ZnO content of 15.1% was adopted to ensure consistent retardation in setting time. The use of an accelerator/homogenized EAFD ratio of 0.25 for CN and CF has shown significant reduction in setting time more than CC. Additional reduction was achieved with an increased ratio to 0.5. However, limited effect was noted for CN and CF with a further increase in the ratio compared to CC. Scanning electron microscope (SEM) was used to monitor the microstructure development of selected mixtures at early age. Finally, Prediction models were developed to predict the EAFD and CFCA effects on setting time. The results of this study are important in the quest to develop EAFD from waste byproducts into viable construction material.