Low-temperature calcination of dolomite and its application in the preparation of magnesium phosphate cement

Magnesium phosphate cement (MPC), known for rapid setting and hardening, is often made from hightemperature calcined MgO, increasing costs and carbon emissions. Dolomite, a plentiful magnesium source, offers broader availability and lower costs than magnesite, making it a viable alternative to reduce production expenses and emissions. In this paper, MgO was procured through the calcination of dolomite, and its feasibility for preparing MPC was thoroughly examined. The study focused on elucidating the influence of calcination temperature and duration on the decomposition of dolomite and the reactivity of the resulting MgO. The results indicate that at a calcination temperature of 700 degrees C, the reactivity of MgO initially decreases and subsequently improves with increasing calcination time. The setting time of MPC is influenced by both the activity and quantity of MgO, with an increase in either leading to a reduction in setting time. Specifically, when calcined at 700 degrees C for 1 hr, the MgO exhibits the highest reactivity, resulting in a setting time of merely 5 minutes and a compressive strength of 16.0 MPa after 28 days of curing. Conversely, at a calcination temperature of 750 degrees C, an increase in calcination time leads to a decrease in magnesium oxide reactivity and an extension of the setting time. Microscopic examination of the hydration products of MPC prepared from calcined dolomite revealed that most of these products adhere to the surface of incompletely decomposed dolomite, exhibiting poor crystal development. This phenomenon contributes significantly to the low strength of the MPC matrix. Compared to conventional dead-burned MgO, utilizing a relatively low calcination temperature of 700 degrees C to produce MPCcontaining magnesium raw materials significantly diminishes energy consumption and cost. This approach not only offers promising potential application prospects but also heralds a hopeful future for magnesium phosphate cement, thereby enhancing its overall sustainability and economic viability.