Utilization of Coal Wastes for the Production of Ceramic Materials: A Review

The utilization of coal wastes for the production of ceramic materials provides added value for the coal industry, reduces waste handling and storage costs, minimizes reliance on virgin materials, and mitigates the environmental and health risks posed by waste storage in impoundments. This literature review provides an overview of the methods and patterns observed in the usage of coal ashes and refuse to produce sintered ceramics, glass ceramics, concrete, and geopolymers. The small particle size, reactivity, and high metal oxide content in fly ash improve particle packing and facilitate sintering or alkaline reactions, making it suitable for diverse ceramic applications. Bottom ash is comparatively coarser and less reactive, though it can substitute for sand in concrete manufacturing. The effectiveness of coal refuse in ceramics varies and should be evaluated on a case-by-case basis due to geological differences and varying carbon content. Coal wastes with fine particle size, low carbon and iron content, and high non-iron metal oxide content tend to exhibit improved performance as partial substitutions for ceramic raw materials. Glass ceramics and geopolymers containing fly ash often exhibit similar or improved performance compared to their conventional counterparts. Continued study of fly ash usage in glass ceramics and geopolymers will increase the fraction of fly ash that is reused and drive innovation in materials research. Given the increasing frequency of severe weather events in the northeastern US and the correlation between these events and impoundment failures, there is an exigence for the development of circular economies utilizing coal waste. Glass ceramics and geopolymers represent a broadening market for coal wastes. Continued research and innovation in coal waste management are necessary to align with climate and sustainability objectives while maintaining coal's advantage as a reliable and globally dominant energy source.