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Thermomechanical and Thermochemical Behaviour of Silica- and Spinel-Sol-Bonded High-Alumina Refractory Castables

E. Brochen, C. Dannert, M. Thiesen, T. Ibarra, O. Krause, S. Abdelouhab, C. Lang

Journal of Ceramic Science and Technology, Vol. 16, No. 3 (2025), pp. 107-116

DOI: 10.4416/JCST2024-00014

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Abstract

While calcium aluminate cements have become established as a \"workhorse\" for refractory castables (reliable and cost-effective), they nonetheless have certain drawbacks (high risk of explosive spalling during drying, limited resistance to acidic slags and ashes) and, after years of optimization, only limited potential remains for further improvements. By contrast, colloidal suspensions (sols) are increasingly used as bonding solutions in the industry (silica sols) and, despite their current limitations (providing low green strength and limited refractoriness), they have much to offer. Especially alternative sols, such as mullite and spinel sols, are attracting attention for improving the refractoriness and resistance to corrosion of sol-bonded castables, but studies regarding their performance at high temperature are extremely sparse.The thermomechanical and thermochemical behaviour of silica- and spinel-sol-bonded high-alumina refractory castables was investigated using wedge splitting measurements, high-temperature thermal shocks and induction furnace tests. Silica-sol-bonded high-alumina refractory castables are rather weak when compared to high-alumina refractory bricks, but they are able to develop more ductility before weakening and exhibit improved resistance to high-temperature thermal shocks. The use of spinel sols considerably improved the high-temperature mechanical and fracture resistance of the sol-bonded high-alumina refractory castables without degrading their resistance to thermal shocks. The spinel sols even slightly improved the resistance of the castables to corrosion.

Keywords

Refractory castables, colloidal-bonded, high-temperature thermal shocks, wedge splitting test, corrosion resistance.

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