MICROMECHANICS OF ITZ-AGGREGATE INTERACTION IN CONCRETE: CRACK INITIATION

Author(s): Markus Königsberger, Bernhard Pichler and Christian Hellmich
Book Title: RILEM International Symposium on Concrete Modelling - CONMOD 2014
Editor: Kefei Li, Peiyu Yan and Rongwei Yang
ISBN: 978-2-35158-139-1
e-ISBN: 978-2-35158-140-7
Publisher: RILEM Publications SARL
Publication year: 2015
Pages: 215-221
Total Pages: 7
Language: English

Abstract: Macroscopic crack initiation in concrete, defining the elastic limit of the material, starts around the aggregates in the region of the interfacial transition zones (ITZs) either by separation of cement paste from the aggregates or by microcracking inside the ITZs. In our multiscale model, concrete is considered to be a matrix-inclusion composite consisting of spherical coarse aggregates embedded in a mortar matrix, which, in turn, is represented as a matrix inclusion composite (on a smaller scale) consisting of sand grains embedded in a cement paste. At both scales, however, two-dimensional ITZs are considered to establish perfect bond between the inclusions and the surrounding matrix. At the scale of some micrometers, this ITZs are resolved as three-dimensional spherical shells. This three-scale approach is used to get access to microscopic interface tractions and ITZ stresses which are the basis for upscaling microscopic cracking functions for ITZ-aggregate separation and for ITZ failure, respectively, to the material scale of concrete. This paper reviews some major findings of the stress concentration and the related cracking characteristics, and also summarized sensitivity analyses and the comparison to experimental data.

Online publication: 2015
Publication Type: full_text
Public price (Euros): 0.00