Effects of particle size and crystalline phases developed after thermal shock cycles on the physical properties and mechanical resistance of cordierite-mullite concrete mixes

The main target of this investigation is the analysis on the effect of the particle size in two Cordierite-Castables. The Cordierite-Mullite phase in refractory mixes can be performed using raw materials with magnesium oxide in its compositions, such as, H₂Mg₃(SiO₃) ₄ mineral talc, or commercial dead burned magnesite which is available in the market with different MgO content. In this study a 90% MgO was utilized. This mineral was selected in place of mineral talc because this contains more impurities in its composition, which tend to perform a more amount of liquid phases with low fusion points. After the two mixes were fired, at 1260°C, the cordierite phase was quantified in each mix by DRX. Samples were calcined and subjected to several cycles of thermal shock, heating the samples up to 850°C with an electrical furnace and pouring them into a container with water at room temperature. This cycle was performed until cracking was complete for each mix. Samples designed with a major amount of fine material, support more cycles of thermal shock, as for example, 272 cycles. Samples designed with a more amount of coarse material resisted only 152 thermal shock cycles.