Abstract
This study investigates the use of chloride-free calcium-based chemical accelerators in ordinary concrete incorporating freshly homogenized electric arc-furnace dust (EAFD). The utilization of calcium nitrite (CN) and calcium formate (CF) counteracts the negative impact of elevated zinc oxide content in fresh EAFD. The presence of ZnO dramatically delays the setting time of cement in paste and concrete. In this study, EAFD was used in different replacement levels varied from 0 to 12% of cement. The incorporation of EAFD in concrete increased the setting time of concrete by up to 68 h. However, the presence of chemical accelerators enabled a significant reduction in setting time. The hydration reaction formed around cement grains due to the reaction between ZnO in EAFD and portlandite (Ca(OH)2) is responsible for the delay in setting time. This delay could be overcome under the influence of a concentration gradient due to the effective chemical accelerator dosage. The use of EAFD in concrete showed similar strength to silica fume (SF) mixes. The efficiencies of CN and CF rely on their dosage and EAFD content. It is concluded that the effective chemical accelerator-to-EAFD ratio plays a vital role in mitigating the extensive delay in setting time to practically feasible values. The mixture containing 4% CN and 4% EAFD was identified as the best concrete mixture.
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