Improvement of the thermal properties of alkali-activated fly ash after high temperature by the Fe-based solid wastes

Compared with Portland cement, AAM was selected as the high-temperature resistant material. But there is still a trend toward a significant reduction in compressive strength at 600 degrees C and 800 degrees C. Thus, in this paper, the Fe-based solid wastes, i.e., copper slag and iron tailing, were used to improve the compressive properties of fly ash-based AAM after high temperatures. The result shows that the residual compressive strength of the Fe-based solid waste samples is higher than that of the blank sample. The residual compressive strength increases by about 20 % at 800 degrees C. Though the results of SEM-EDS, MIP, and XPS experiments, the mechanism of the effect of Fe -based solid wastes on the AAM could be summarized as follows: the iron element in the Fe -based solid waste samples is more concentrated after high temperature, which may be caused by the melting of the original iron mineral phase into a new mineral phase, filling the crack gap. And the formation of the Fe-O-Si amorphous phase would improve the densification of samples, resulting in the improvement of compressive strength.