Dolomite used as raw material to produce MgO-based expansive agent

In this paper, the manufacture of MgO-based expansive agent using dolomite as raw material was studied. The decomposition of dolomite was discussed at first by DTA-TG analysis and on the crystalline view. On the characteristics of decomposition of dolomite, the authors think it is possible to use dolomite as raw material, but the silica-bearing mineral is considered to combine the CaO released from dolomite to form silicate. The phases of MgO-based expansive agent are mainly MgO, C₂S and a little amount of CaO. The expansion of resulting expansive agents by autoclaving testing and hot water curing at 80 °C shows that the MgO-based expansive agents have desired expansion. If the burning temperature and burning time, dosage in cement are controlled according to the requirement of concrete construction, the MgO-based expansive agent can be used to compensate the shrinkage as designed.