Study on the source of activity and differences between modified and unmodified magnesium slag as a filling cementitious materials

Abstract

The best alternative for producing magnesium metal cleanly has emerged as the realization of magnesium slag resource usage. Magnesium slag is simple to pulverize, low activity, and difficult to utilize. For this, our team proposed adding an optimization agent before reducing metal magnesium to obtain modified magnesium slag (MMS). This study aims to contrast the differences between MMS and unmodified magnesium slag' (UMS) cementitious characteristics. First, it was determined how MMS and UMS differed in terms of cementation activity. Then, the performance variations of the filled cementitious materials (MF-A, MF-B, and UMF), which were made by combining fly ash (FA) with MMS and UMS, respectively, were compared. The findings indicate that, the main mineral compositions of MMS and UMS are β-C2S and γ-C2S, respectively, MMS exhibits non-swelling and non-powdering properties compared with UMS. The 28 d activity indices for MMSA and MMSB were respectively 90.78% and 88.48%, higher than those for UMS by 23.02% and 20.72%. The early hydration reactions of MF-A and MF-B were more rapid, per the hydration heat data. Additionally, microscopic analysis revealed that the unconfined compressive strength of MF-A at 28 d (8.39 MPa) was much higher than that of UMF (4.99 MPa), which was mostly caused by the difference in the concentration of hydration products. In conclusion, MMS has higher hydration activity and stable properties, which can be combined with FA and other applications in the field of mine filling to achieve resource utilization.