New Insight on Developing MgO–SiO 2 –H 2 O Gel Bonded MgO Castables
Elkem Silicon Materials, Kristiansand/Norway
Revision
Volume 6, Issue 3, Pages 83 - 88
Abstract
It is well known that brucite forms during MgO hydration and this causes volume expansion and subsequent cracking – a phenomenon commonly called “slaking”. Although much research on lab-scale small prisms has demonstrated that the interaction between MgO and SiO 2 prevents slaking, the mechanism of MgO hydration has not been well understood. Hence, magnesia castables have not been widely used. To overcome problems related to slaking, a new specialty product, SioxX-Mag, has recently been developed for cement-free MgO castables based on MgO–SiO 2 –H 2 O bond. Samples from larger, dried blocks were characterized by XRD. Using SioxX-Mag in combination with microsilica, cracking caused by brucite formation is suppressed. The results demonstrate that the dosage of microsilica and the type of dispersant play essential roles in the crack formation in large specimens. Furthermore, the compatibility of SioxX-Mag with different types of MgO aggregates, medium to high-grade dead burned magnesia and olivine, has been evaluated. High-performance, self-flowing MgO–SiO 2 –H 2 O gel bonded MgO castables have been developed, exhibiting good workability and setting behavior while hot-properties are maintained.
Keywords
microsilica gel-bond, MgO hydration, MgO castables, slaking
References
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