Fabrication of high-performance glass-ceramics from blast furnace slag and coal fly ash

Glass-ceramics were prepared through the powder sintering method by directly using blast furnace slag and coal fly ash (CFA), both of which are glassy state dominated. Due to the high basicity and fast crystallization characteristic of the blast furnace slag which could hinder sintering densification, the high energy ball milling treatment of blast furnace slag together with CFA (ultra-low basicity waste) was conducted to refine the particle size and achieve a "cold adjusting" effect, thereby promoting the sintering ability of the blast furnace slag. The effects of CFA addition content, particle size of raw materials and sintering temperature on sintering behavior, crystalline phase, micro-structure and mechanical properties of as-prepared glass-ceramics were investigated. Results showed that the addition of CFA facilitated the densification of blast furnace slag during sintering process. The densification degree and flexural strength increased with the increase in the proportion of CFA addition, reaching the highest values when the addition ratio was 50 %. Meanwhile, the flexural strength first increased with the rise in sintering temperature and then experienced a slight decrease at 1000 °C. When the CFA addition ratio was 50 % and the sintering temperature was 950 °C, the flexural strength of sintered samples reached 168.95 MPa, with an acid resistance of 96.86 % and an alkali resistance of 98.99 %.