Mechanical activation of coal gasification slag for one-part geopolymer synthesis by alkali fusion and component additive method

Coal gasification slag is an industrial by-product obtained after valuable gas production from coal gasification. There is little research concentrating on geopolymer synthesis using coal gasification slag. In this study, the suitability of mechanical activation for coal gasification slag-based one-part geopolymer synthesis has been investigated by alkali fusion and component additive method. The results showed that coal gasification slag ground at 20 min (S-20) presented the finest particle size, and the corresponding geopolymer (G-20) had the highest compressive strength. The reaction degree test proved that mechanical activation improved the reaction degree of geopolymers. However, different mechanical activation times had little influence on the reaction degree of geopolymers. It can be concluded that the particle size of the coal gasification slag was the primary reason for the compressive strength in geopolymers, and finer coal gasification slag led to higher compressive strength. Fine coal gasification slag additive particles could fill the pores of the geopolymer or be connected by the newly formed hydration products. This helped to form a dense, uniform, and compact matrix and increased the compressive strength of the geopolymers. As the mechanical activation time went up, the coal gasification slag particles got bigger, and the coal gasification slag additive's filling effect got weaker, which decreased the compressive strength of geopolymers. Furthermore, this study gave a new explanation of the role of the coal gasification slag additive in one-part geopolymer, which improved the feasibility of the other materials for one-part geopolymer synthesis by the alkali fusion and component additive method.