Activation of Low-Quality Coal Gangue Using Suspension Calcination for the Preparation of High-Performance Low-Carbon Cementitious Materials: A Pilot Study

Abstract

Although the calcination-based activation of coal gangue is important for its valorization in the form of cementitious materials, the related works mainly focus on high-quality coal gangue, neglecting its low-quality counterpart. To bridge this gap, we herein conducted the pilot-scale suspension calcination of low-quality coal gangue; explored the effects of calcination temperature, particle size, and O2 content on the phase composition of the calcined product, kaolinite decomposition, decarbonization, and silica/alumina dissolution; and evaluated calcination-product-based cementitious materials. Under optimal conditions (temperature = 875–900 °C; particle size = 39.71–46.84 μm; and O2 content = 12–14%), the carbon content of the calcined product equaled 1.24–1.87 wt%, and the dissolution rates of activated alumina and silica were 77.6–79.5% and 49.4–51.1%, respectively. The 28 d compressive strength (50.8–55.7 MPa) and true activity index (98.8–108.4%) of the cementitious material prepared at a calcination product dosage of 30–38 wt% met the standard of 42.5 grade cement. This study demonstrated the suitability of suspension calcination for the preparation of high-performance low-carbon cementitious materials from low-quality coal gangue, thus providing a basis for further industrialization and technological development.