Meso-mechanical modelling of damage in concrete using discrete element method with porous ITZs of defined width around aggregates

Abstract

The article deals with two-dimensional mesoscopic numerical results of fracture in concrete at the aggregate scale in a beam with a notch under bending. The focus was on the effects of both initial micro-porosity in ITZs and aggregate roughness on the load-deflection curve and propagation and location of micro- and a macro-damage. An improved discrete element method (DEM) was used for concrete to predict its strength, brittleness and fracture. A phase concrete description was used to explicitly take its heterogeneity into account. Concrete included aggregate, mortar, interfacial transition zones (ITZs) and macro-pores. In contrast to existing approaches, ITZs were simulated as porous mortar zones around aggregates with a defined width (without reducing mechanical properties). The real shape and place of aggregates in the beam were established in numerical calculations upon on x-ray micro-CT scans. The findings presented in this paper offer a new perspective as to the understanding of micro-cracking formation in concrete under loading.