Contribution to the understanding of the high temperature behavior and of the compressive creep behavior of silica refractory materials

Some silica (95% SiO2) refractory materials were selected and characterized by their chemical and crystallographic compositions, microstructure, refractoriness under load and bending strength versus temperature. Creep tests were realized at temperature higher than 1500 °C, using the differential method. This part of the work was mainly focalized on one material. Complementary tests: annealing treatment followed by crystallographic analysis, measurement of dimensions variation and microstructure observation were also realized. Results of annealing and creep tests demonstrate a competition between shrinkage and a volume expansion of the material, associated with a modification of crystallographic composition and of the microstructure. Results were discussed, compared with literature and a model was developed to explain the behavior and especially the expansion. The high temperature behavior and the compressive creep were explained by the appearance of a calcia–silica vitreous phase and microstructure change. The material expansion at high temperature is explained by calcia migration, from matrix into aggregates. Residual expansion after cooling is partially explained by the cristobalite transformation which induces stress and cracking.