Numerical tests of thermal cracking induced by temperature gradient in cement-based composites under thermal loads

This paper presents the development of a new method to model the thermal stresses and cracks in a heterogeneous cement-based composite material under elevated temperature. Numerical case studies were performed to determine the effects of temperature gradient, heating rate, and variable coefficient of thermal expansion and heterogeneity of materials on the thermal stresses and associated cracking in a cement-based composite material exposed to a transient thermal load. It is found that (1) the settling time and the temperature difference between the surface and the center of specimen increase with the heating rate; (2) the thermal stresses increase with temperature difference, but remain constant if the temperature difference only increases uniformly; (3) most of the cracks induced by temperature gradient are formed before the settling time, and thereafter the thermal mismatch-induced cracks continue to propagate; (4) uncertainties of the occurrence of explosive spalling are probably caused by the thermally induced cracks and the heterogeneities of the constitute materials.