A micro-mechanical parametric study on the strength degradation of concrete due to temperature exposure using the discrete element method

The present paper investigates the extent of damage caused by temperature on concrete samples. This is accomplished by a parametric approach using a 2-phase discrete element model which incorporates temperature as a global variable. Two factors of concrete degradation have been considered in this study: the thermal incompatibility of the aggregates-mortar composite and the degradation of the bonds between the particles. The base models of this parametric study are created using concrete specimens tested in the laboratory after been exposed to elevated temperatures. Using these base models, the coefficient of thermal expansion (CTE) of aggregate and mortar particles are varied independently and the discrete element model is subjected to increasing temperatures. The residual strength of the thermally-cracked particle assembly is then determined under compression. The results of 36 different combinations of the CTE show the extent of damage that can be induced due to thermal incompatibility of the particles. The variation of residual strength and residual stiffness are discussed in terms of the number of inter-particle bonds that break under rising temperature.