Fracture Process Zone in Refractory Castables after High-Temperature Thermal Shock

J. Schnieder1, N. Traon1, S. Etzold1, T. Tonnesen1, R. Telle1, A. Tengstrand2, A. Malmgren2, E. Nylund2

1 RWTH Aachen University, Institute of Mineral Engineering, 52070 Aachen/Germany
2 KTH Royal Institute of Technology, 10044 Stockholm/Sweden

Revision 01.12.2015, 11.01.2016

Volume 8, Issue 2, Pages 74 - 80


Thermal shock damage is an important issue for the refractories industry. To understand the microstructural behaviour and with it the thermoelastic properties during thermal shock treatment are key topics for high performance refractory materials and their development. Most ceramic materials exhibit a critical temperature difference (ΔTc) as a minimum temperature required for fracture initiation. Refractories exhibit within their heterogeneous structure already pores, aggregates of different size and cracks. To understand the influence of the temperature difference (ΔT) and the temperature level, a new high temperature thermal shock furnace was designed and constructed. Unlike standard thermal shock tests with compressed air or water, the new furnace’s two separately heatable and interconnected chambers enable the transfer of samples between two high temperatures without exposing them to the surrounding atmosphere at room temperature. To understand the effect of rapid temperature changes, the natural aggregate andalusite and the synthetic aggregates Al2O3–ZrO2–SiO2 and Al2O3–ZrO2 are incorporated in a model low cement castable formulation based on tabular alumina. The influence of these aggregates on the elastic and thermomechanical properties is examined and correlated to the microstructure.


Refractories, high temperature thermal shock, eutectic aggregates, liquid phase bridging


[1] Boccaccini, D. N.; et. al.: Service life prediction for refractory materials. J. Mater. Sci. 43 (2008) 4079–4090 [2] Chandler, H. W.: Thermal shock of refractories, Refractories Appl. and News 10 (2005) [2] [3] Hasselman, D. P. H.: Unified theory of thermal shock fracture initiation and crack propagation in brittle ceramics. J. Amer. Ceram. Soc. 52 (1969) [11] 600–604 [4] Bradt, R. C.: Fracture of refractories, in: Refractories Handbook, Ed. C.A. Schacht, Chapter 2, 11–38 [5] Bradt, R. C.: Crack extension in refractories. Proc. Unitecr ’11; Kyoto, 30.10.-2.11.2011, Paper No. 2-D-5 [6] Harmuth, H.; Bradt R. C.: Investigation of refractory brittleness by fracture mechanical and fractographic methods. Refractories Manual 2010, 6–10 [7] Miyaji, D. J.; Tonnesen, T.; Rodrigues, J. d. A.: Eutectic aggregates containing refractory castables: What are their effects on fracture energy and thermal shock damage resistance? Proc. UNITECR ’11, Kyoto, 30.10.–2.11.2011, Paper No. 2-D-3. [8] Miyaji, D. J.; Otofuji, C.; Rodrigues, J. d. A.: The load-displacement curve of steady crack propagation: An interesting source of information for predicting the thermal shock damage of refractories. Proc. UNITECR ’13, Victoria, Paper No. 17–10 [9] Garvie, R. C.: Zirconium dioxide and some of its binary systems, in: High-Temperature Oxides, Vol. 5-II., Ed. Alper, A.M., New York 1970, 117–166 [10] Pandolfelli, V. C.; et al.: Influence of mullitezirconia aggregate addition on the thermomechanical properties of high-alumina refractories. Unitecr ’93 Congress, São Paulo, 1993 [11] Pandolfelli, V. C., et al.: Evaluation of thermomechanical properties of alumina refractories containing a fused mullite-zirconia aggregate. Unitecr ’95, Kyoto, Japan, 2, 1995 [12] Miyaji, D. J.; Tonnesen, T.; Rodrigues, J. d .A.: Fracture energy and thermal shock damage resistance of refractory castables containing eutectic aggregates. Ceramics Int. 40 (2014), 15227–15239 [13] Tessier-Doyen, N.; Glandus, J. C.; Huger, M.: Anisotropic untypical Young’s modulus evolution of model refractories at high temperature, J. Europ. Ceram. Soc. 26 (2006) 289–295 [14] Kakroudi, M. G.; et al.: Anisotropic behaviour of andalusite particles used as aggregates on refractory castables. J. Europ Ceram. Soc. 29 (2009) 571–579 [15] Schnieder, J.; et al.: Crack formation and shape of fracture surface in tabular alumina based castables with addition of specific aggregates. J. of Ceramic Sci. and Technol. 5 (2014) [2] 131–136 [16] Schnieder, J.; et al.: Influence of eutectic aggregates in castables on the thermal shock resistance. Proc. Int. Coll. on Refractories 2013, Aachen [17] Schnieder, J.; et al.: Influence of the thermal shock temperature difference on the microstructural damage and the crack propagation in modified high alumina refractory castables. Proc. Unified Int. Technical Conf. on Refractories 2015, Vienna, September 15–18 [18] Traon, N.; et al.: Influence of andalusite, Al2O3– ZrO2–SiO2 and Al2O3–ZrO2 addition on elastic and mechanical properties of high alumina castables. Interceram Refractories Manual 11 (2014) 290–294 [19] Schnieder, J.; et al.: Microstructural damage of modified high alumina castables after several thermal shock cycles under specific experimental conditions. Proc. 57. Int. Coll. on Refractories Aachen, September 2014 [20] Salvini, V. R.; Pandolfelli, V. C.; Bradt, R. C.: Extension of Hasselmans thermal shock theory for crack/microstructure interaction in refractories. Ceramic Int. 38 (2012) 5369–5375


Göller Verlag GmbH