Calcined Coal Gangue and Clay Shale for Cementitious Materials Without Clinker
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Coal gangue and clay shale usually contain more than 70 % SiO2 and Al2O3, which have potential pozzolanic activity when calcined at suitable temperature. In this study, the feasibility of utilizing calcined coal gangue and clay shale in the production of multiple cementitious materials was assessed under the condition of no cement clinker. The minerals and chemical composition of coal gangue and clay shale were characterized by analytical techniques such as X-ray diffraction (XRD) and X-ray fluorescence analysis (XRF). The optimal calcining temperature of coal gangue and clay shale was obtained through differential thermal analysis (DTA), and the activity evaluation method was conducted to get the optimal calcining procedure. The results showed that, the optimal calcining procedure for coal gangue and clay shale to obtain the best pozzolanic activity is as following: coal gangue and clay shale under the ratio of 7:3 were calcined at 780 °C for 2 h, and then quickly cooled in the air. The cementitious materials, which were prepared by calcining coal gangue, clay shale, slag, gypsum and CaO (as activator) under the ratio of 45:35:5:15, could reach the strength of class P.C. 32.5 of the Chinese standard GB175-2007.
KeywordsCalcination Temperature Cementitious Material Coal Gangue Cement Clinker Pozzolanic Activity
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