Rapid Heating of Concrete: Is Spalling an Issue of Poromechanics?

This paper describes recent findings of an experimental and computational program to investigate the effect of mismatch when concrete materials are subjected to rapid heating and drying. The main foci are interaction effects in heterogeneous composites when the constituents with different thermal expansion and hygral shrinkage properties are subjected to severe environmental load scenarios. This paper addresses the question, whether spalling in concrete materials is caused (a) by the contrast of constituent material properties, or (b) by thermal-shock instabilities of subdomains subjected to compression. This discussion reaches beyond the traditional arguments of thermal stress spalling due to restrained thermal expansion, or due to pore pressure spalling caused by the phase change of the free pore water under high temperature.