Modeling of the ITZ zone in concrete: Experiment and numerical simulation

The discovery of the Interfacial Transition Zone (ITZ) by Farran in 1956 initiated a new era in the study of the behaviour of concrete. Acknowledged as the weak link, this ITZ was studied extensively, numerically as well as experimentally. While the complementary experimental tests illustrated the visual behaviour of this specimen under increasing monotonic compression loading, a perfect bond within the ITZ has also been studied by using finite element analysis for comparison purposes. Finite element analysis was used to evaluate the degree of correctness and precision of the proposed ITZ model. This paper discusses the use of the cutoff bar in finite element modeling, representing the ITZ of a single aggregate (inclusion) in a mortar matrix. Experiments were conducted to investigate the influence of the ITZ model on the single inclusion specimen\'s strength. The model was tested for some inclusions that varied in dimension and shape. The effect of inclusion shape on the stress concentrations of the specimens was examined. The aim of this research work is to propose a simple yet accurate ITZ model to be used in the commercially available finite element software packages.