Effect of the hydrotalcite formation on the fracture behavior and corrosion resistance of HA-bonded alumina-spinel castables

Hydratable alumina-bonded castable is a promising non-cement bonded refractory for ladle lining. An in situ formation of layered double hydroxides (Mg-Al hydrotalcite, M-A-H) using reactive MgO powders is proposed as a means of enhancing the castables during curing, drying, and after the high-temperature treatment. The formation of hydrotalcite, spinel transformation, pore structure, mechanical properties, fracture behavior, and slag corrosion resistance have been systematically investigated. The results indicate that the hydrotalcite formation is governed by the hydration reactivity of MgO, which promotes the formation of Mg(OH)2 as an intermediate hydrate, and the ultimate growth of hydrotalcite. The residual MgO and newly formed hydrotalcite are eventually transformed into micron size and submicron size spinel, respectively. This structural evolution contributes to an optimized pore structure and microstructure, enhancing the castables. The ultimate pore structure and enhanced interfaces between aggregate and matrix facilitate the improvement of toughness and slag corrosion/penetration resistance.