Abstract
In this paper, the attention is paid to investigation of the importance of the interfacial transition zone (ITZ) in selected fine-grained cement-based composites for the global fracture behaviour. This is a region of cement paste around the aggregate particles which specific features could have significant impact on the final behaviour of cement composites with a crack tip nearby this interface under applied tension. The aim of this work is to show the basic interface microstructure by scanning electron microscopy (SEM) done by MIRA3 TESCAN and to analyse the behaviour of such composite by numerical modelling. Numerical studies assume two different ITZ thicknesses taken from SEM analysis. A simplified cracked geometry (consisting of three phases – matrix, ITZ, and aggregate) is modelled by means of the finite element method with a crack terminating at the matrix–ITZ interface. ITZ’s modulus of elasticity is taken from generalized self-consistent scheme. A few conclusions are discussed based on comparison of the average values of the opening stress ahead of the crack tip with their critical values. The analyses dealing with the effect of ITZ’s properties on the stress distribution should contribute to better description of toughening mechanisms in silicate-based composites.
Highlights
Cement-based composites belong to traditional and broadly used building materials [1]
Composites 04042016 and 09052016 As it was mentioned above the thickness of interfacial transition zone (ITZ) was taken from scanning electron microscopy (SEM) measurement and in the composite 04042016 it was 55 μm, while in the composite 09052016 it was 40 μm
These pilot results can lead to more reliable description of toughening mechanisms of composites of this kind. Further it can be used for design of more resistant silicate-based composites. The authors focused their attention on the evaluation of the influence of the interfacial transition zone on the stress distribution in the cracked specimen
Summary
Cement-based composites belong to traditional and broadly used building materials [1]. Despite their long-term using, the investigation of damage of elements made of such materials under static loading is still developing. The individual components of primarily considered two-stage composite, cement paste and aggregate, show very often brittle elastic behaviour. This difference in cement-based composites behaviour is caused by development of multiple microcracking predominantly in the so called interfacial transition zone (ITZ) [2] and others toughening mechanisms. The aim of this paper is quantification of basic mechanical fracture parameters of selected fine-grained cement-based composites – static modulus of elasticity, fracture toughness and fracture energy and investigation of effect of ITZ between cement matrix (MTX) and aggregate (AGG) on stress distribution in cement based composite with crack terminating at the ITZ–MTX interface
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