Performance improvement of free CaO containing magnesia with ZrSiO4 addition

Free CaO containing magnesia has limited application due to poor resistance to hydration, slag penetration and thermal shock. This work aimed to improve the performances of such magnesia by introducing mi-croscale ZrSiO4 powder. The results showed that the relative density of the specimens reduced from 92.1 % to 90.9 % when adding 1 wt% ZrSiO4 due to formation of Ca2SiO4 and CaZrO3, but then gradually increased to 96.2 % with further increasing ZrSiO4 to 7 wt% owing to the enhanced mass transfer and MgO grains growth caused by generation of c-ZrO2 and CaMgSiO4. The addition of ZrSiO4 obviously improved hydration re-sistance of the specimens, whose weight gain rate after the hydration test reduced significantly from 0.38 % to 0.01 % as the ZrSiO4 increasing from 0 wt% to 7 wt%. Thermal shock resistance (TSR) of the specimens reduced slightly when adding 1 wt% ZrSiO4 owing to the presence of more irregular pores, but then im-proved dramatically with further increasing ZrSiO4 due to the reduction in thermal expansion coefficient and occurrence of crack deflection. Besides, slag penetration was accelerated in the specimen with 1 wt% ZrSiO4 due to its lowered densification, while further increasing ZrSiO4 effectively improved the slag pe-netration resistance, attributing to the increase in MgO grain size and density and formation of the CaZrO3 containing dense layer preventing further slag infiltration.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

The addition of microscale ZrSiO4 powder improved the performance of free CaO containing magnesia, resulting in increased relative density, improved hydration resistance, enhanced thermal shock resistance, and improved slag penetration resistance.