MICRO-SCALE AIR VOID STRUCTURES IN CONCRETE AND THEIR EFFECT ON FAILURE BEHAVIOR

Year 2019, Volume: 20 Issue: 3, 334 - 345, 26.09.2019

Baris Arslan , Hasan Selim Şengel , Mehmet Canbaz

https://doi.org/10.18038/estubtda.536440

Abstract

Tomography images and image processing
methods are extensively employed by researchers to investigate the micro-dimensional
air voids that are formed in the internal structure of concrete.  Finite element method-based fracture analysis
is required to investigate the effect of the mechanical behavior of concrete
and micro-dimensional crack development; micro-dimensional voids cannot be
experimentally observed because of their small scale.  Although concrete that is exposed to uniaxial
compression remains in the elastic region, realistic brittle failure can be
achieved using the damage plasticity model, which considers the effect of
tension cracks that form around micro air voids, which in turn enhance cracking
development and the compressive strength of concrete. Within the scope of this study, concrete
cubes with a side dimension of 15 cm were prepared. Three groups of these cubes
are composed; each group contains three specimens. The first group contains
additive-free control specimens and the remaining two groups contain specimens that
are mixed with two different ratios of air-entraining admixtures. After the
concrete specimens were created,  core samples were prepared and scanned with micro
computed tomography.  These 2D and high-resolution
images are modeled using the image processing software Simpleware and exported
to the FEM-based analysis software Abaqus. 
The volume, void ratio and mass properties of fresh and hardened
concrete, which are experimentally obtained, are compared with the physical
properties of 3D-modeled specimens.  Based
on the mass and volume analyses, these 3D models, which have micro-dimensional
air voids that are assigned with the parametrized CDP material properties were
simulated, and a uniaxial compression tests and fracture analysis were performed.  According to the analysis results, the
relations between crack development and quantity and the distribution of
entrained air were discussed.

Keywords

concrete, micro air voids, μCT image processing, FEM

Supporting Institution

ESOGU Scientific Research Fund (ESOGU-BAP)

Project Number

ESOGU-BAP grant number 201315023

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