Composite behavior of concrete materials under high temperatures

Abstract This study examines the performance of concrete under elevated temperatures at the meso-scale level of observation where aggregate particles and the embedding hydrated cement paste form interacting continua. Decomposing concrete into these two constituents leads to mismatch of the thermal and hydraulic transport properties and hence to self-equilibrating internal stresses introducing progressive damage of the mechanical response behavior of concrete. Thereby the internal stresses are disregarded by the macro-scale level approach when the heterogeneities are replaced by equivalent effective material properties using homogenization. In other terms, the macroscopic approach eliminates the contrast among the individual constituents and consequently negates the development of stresses causing pervasive microcracking in concrete. The current study resolves concrete into its main components, the aggregate particles and the cement paste, bonded by a weak interface transition zone that reduces to some extent the mismatch between the two constituents. The study illustrates the magnitude of the stress state in representative concrete specimens and the resulting damage evolution under high temperatures.