Influence of the particle size distribution of coarse-grained refractories on the thermal shock performance

This study investigated the influences of the particle size distribution (characterized by the amounts of fines and coarses and by the maximum particle size (1|3 mm)) and the compaction pressure (50|100 MPa) of die-pressed bars on the behavior of the bulk density, cold modulus of rupture (CMOR) and Young’s modulus E during five thermal shocks (TS). Highest densities were obtained for wide particle size distributions with densest packed coarse aggregates, a slight excess of lubricating fines and a high compaction pressure. Highest CMOR and E were obtained for the same parameters with the exception of a maximum particle size of 1 mm inducing lower flaw sizes. Independent on the compaction pressure, lowest CMOR losses during TS were obtained for a wide particle size distribution with a high number of aggregates constituted of medium-sized grains and densest packed coarses. Supposedly, crack deflection and contact shielding toughening occurred. During TS, E behaved differently. Probably, E was low when there were many flaws. During TS, these led to a large process zone and high decrease of E whereas for batches with higher initial E a crack could propagate with less microstructural interactions giving supposedly a smaller process zone and a reduced decrease.