Spalling　resistance　of　refractory　bricks　containing　60－99％　zircon　was　investigated　by　measuring　3－ point　bending　strength　of　specimens　quenched　into　water　from　various　temperatures．Bending　strength and　Young’s　modulus　of　zircon　bricks　quenched　decreased　continuously　with　increasing　quenching temperature　difference，because　the　fairly　large　cracks　in　the　bricks　propagated　stably　under　various conditions　of　thermal　shock． 　Spalling　resistance　of　zircon　bricks，as　measured　by　the　relative　retained　in　a　water　quench，correlated　well　with　the　thermal　stress　resistance（crack　stability）parameter　Rst　and　the　thermal　shock　damage　resistance　parameter　R’’’’．

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