Performance and energy calculation on a green cementitious material composed of coal refuse

Coal refuse as industrial solid waste has become great threats to the environment. To activate coal refuse is one practical solution to recycle this huge amount of solid waste as substitute for ordinary Portland cement (OPC). Compared with conventional cement production, successful development of this new material could potentially save energy and reduce greenhouse gas emissions, recycle vast amount of coal wastes, and significantly reduce production cost. Coal refuse was confirmed as a pozzolanic material, which enhances its durability performance. In this experiment, 60 % of the OPC was substituted with the pozzolana mixture (30 % coal refuse + 25 % slag + 5 % FGD gypsum), which is an optimal solution for the creation of good-performance cementitious material. Compared with OPC, the 60 % pozzolana blended sample has a much higher resistance to the alkali-silica reaction and Cl ion penetration. In addition, microanalyses of the activated coal refuse by XRD demonstrated that some of the mineral phase changes in coal refuse were related to the performance of the cementitious material. For example, the transformation of kaolinite into metakaolin and the dehydroxylation of muscovite enhance the resistance of the cementitious material to the alkali-silica reaction and Cl penetration, respectively. Compared with conventional cement production by calculation, successful development of a new thermal activation process (800 °C) to convert coal refuse into desirable pozzolanic material for producing the new material would potentially save energy around by about 50 %, reduce greenhouse gas emissions by about 67 %.