Beneficiation of ponded coal ash through chemi-mechanical grinding

•Ponded coal ash are ideal waste for chemi-mechanical beneficiation.•Chemi-mechanical grinding promotes the formation of extrext pozzolanic reaction sites.•Breakdowns in crystallinity facilitates the increase in reactive (amorphous) phases.•Breakdown in large particles allows for an increase in reactivity.•Beneficiation may allow for the reuse of ponded coal ash as a supplementary cementitious material. Four samples of low quality ponded coal ash were subjected to a chemi-mechanical beneficiation technique to test improvements to traditional grinding methods. The addition of water into this beneficiation process can further increase the reactivity of the subjected materials. Changes to the reactivity of these ponded ashes and their structure were analyzed utilizing ATR spectroscopy, X-Ray Diffraction, and Scanning Electron Microscopy. The results show a drop in structural order, smaller particle size, and a 7 to 70 percent increase in amorphous content. These improvements are in contrast to an increase in crystallinity observed with the more traditional dry grinding technique. ATR IR spectroscopy confirms the formation of additional terminal silanol groups after the chemi-mechanical grinding process suggesting a further increase in pozzolanic reactivity. These results suggest that the proposed modification to the beneficiation process does not interfere with the ash improvements observed with traditional grinding but further improves the ash reactivity due to the formation of additional silanol groups. Additionally, ponded ashes (being hydrated) are the ideal source material for this beneficiation process, allowing for a larger quantity of this material to be reutilized efficiently.