Identification and Activation of Coal Gangue and Performance of Limestone Calcined Gangue Cement

Abstract

Gangue, a typical waste associated with the coal mining process in northern China, was characterized before and after thermal treatment by XRF, XRD, TGA-DSC, and SEM. The pozzolanic reactivity of calcined gangue with different calcined temperature was tested by standard mortar strength and R³ calorimetry test. The performance of blended cement was evaluated by mortar strength and flow. The XRD and TGA-DSC analyses showed that the main minerals that present in the raw gangue were kaolinite, and a small amount of carbon-based compounds and metakaolin were almost the only phase in calcined gangue. After thermal treatment and depending on the temperature, it showed very high reactivity especially combined with limestone. The strength property of limestone calcined gangue cement with 45% replacement of clinker was higher than reference cement (CEM I 42.5 N) on 7 and 28 days. Furthermore, it is found that the calcined gangue has less influence on the workability of LC³ according to particle morphology compared with a typical calcined clay, based on the results of SEM observation.