Influence of Na sub(2)CO sub(3) on Hydration Resistance of MgO-Al-C Bricks

To improve the hydration resistance of MgO-Al-C bricks, Na2CO3 was chosen as an additive through thermodynamic calculation. MgO-Al-C refractories were prepared by using Si, Na2CO3 or both as additives. The effects of additives on the hydration resistance of specimens were investigated. XRD was conducted to determine the phase composition. The results showed that the hydration resistance of MgO-Al-C bricks would be improved slightly with addition of only Si due to the densification of the structure. When Na2CO3 and Si were added together, the hydration resistance would be improved remarkably. The mechanism is that Na2CO3 could decompose to give off O2 during heating, which could promote the oxidation of Al metal and inhibit the formation of Al4C3 and AlN.