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A silica brick lining in a furnace that is shut down and restarted weekly has begun to shatter. The likely cause is

  • A.chemical attack by an acid slag
  • B.excessive refractoriness under load
  • C.too low a porosity in the brick
  • D.repeated passage through its crystalline inversion range

Answer: D

The polymorphic changes of silica involve abrupt volume changes, and cycling through them breaks the brick apart. A material of low thermal expansion, such as a suitable fireclay or silicon carbide, would survive the cycling.

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