Michel Coster

Image analysis and mathematical morphology for civil engineering materials

Abstract The scope of this paper is to present the main tools of image analysis to investigate materials and, specially, civil engineering ones. First the acquisition methods are described. The different operators for filtering, segmentation and binary image processing are presented and illustrated on different images. The influence of the observation field on these operators and the bias correction is also introduced. Then the problem of the parametrical characterization is presented: stereological parameters and functions related to size distributions, dispersion and anisotropy. Finally, the model methods based on image analysis are recalled. Some annexes illustrate this paper to precise main basic notions to understand the morphological tools.

Some fields of applications of automatic image analysis in civil engineering

Abstract This paper illustrates the use of automatic image analysis technique to investigate the morphology of cement, concrete and fibre-reinforced concrete. First the methods to be used for powders and secondly for mortar and concrete are introduced. The dispersed phases are characterized by classical morphological parameters: these also enable to accede to the hydration process. The covariances give quantitative information on the homogeneity and dispersion of the different components: gravel, air-voids and cement paste. Air-voids are characterized by granulometric distributions and their mean free paths. Rose of directions gives information on feature orientation: fibres, microcracks for fibre-reinforced concrete, etc. Finally probabilistic models can be used to simulate the microstructure of such materials.

Automatic image analysis and morphology of fibre reinforced concrete

Abstract Automatic image analysis is an efficient tool to quantify the morphology of materials. Moreover, it can aid to understand their mechanical behaviour. Several applications of automatic methods are presented to investigate concrete reinforced by ribbon shaped amorphous cast iron fibres. Introducing ribbons into the plain matrix entrapped air voids. This affected the workability and, later on, the compressive strength of the fibre reinforced concrete (FRC). Both were improved by additions of superplasticizer in order to keep the water to cement ratio constant. The influence of the superplasticizer and fibre contents on the compactness of the FRC was characterized by the dimensional and the spatial distributions of the air voids. The orientations of fibres and microcracks were quantified by Fourier image transforms. Due to the casting procedure of the FRC, the fibres were located in “horizontal layers”, perpendicular to the casting axis. Whatever the direction of compression with respect to the layers of fibres, the microcrack network was getting more and more oriented in the direction of compression as stresses increased. The analysis of fibre and microcrack orientations suggests that, under uniaxial compression, the inelastic strain domain should be characterized by an anisotropic biaxial damage model, whose principal axes are the orthogonal and parallel directions to the layers of fibres.

Towards a model of concrete mesostructure

Abstract This short paper will present a two-dimensional (2D) model of concrete material, based on probabilistic models: it is a combination of a Voronoi tessellation for the gravel, followed by a Boolean model of spherical grains for the air-voids, with elimination of the air-voids–gravel intersections so that there is no contact between them. The model was tested via crossed-covariance. Results on true and simulated structures are in good agreement. This is a first step towards a 3D model.

STUDY OF PHASE DISPERSION IN CONCRETE BY IMAGE ANALYSIS

Abstract The scope of this paper is to investigate by an automatic image analysis technique the dispersion of phases in concrete. Three morphological and statistical tools were used: co-occurrence matrices, and simple and crossed-covariance. It was shown (1) that there is a repulsion between gravel, (2) that gravel and air-voids are surrounded by matrix (cement paste and sand), and (3) that the dispersion of gravel and air-voids is perfectly uniform.

Distances between air-voids in concrete by automatic methods

Abstract In order to access to the air-void distances in concrete by automatic image analysis, three different methods were proposed, used and discussed: half-distances between two voids nearest neighbours, called count-dilation; half-distances between all neighbours, called SKIZ; and distance function. They were utilized in a euclidean and geodesic way. Some of them can replace favourably the manual methods proposed in the different standards.

On a way to material models for ceramics

Abstract This paper presents different probabilistic models which are based (i) for monophased materials on closed random sets (RACSs) and space tessellation such as Voronoi, Johnson-Mehl or Poisson mosaic, and (ii) for polyphazed materials on topologically closed random sets such as Matherons Boolean model, dead-leaves model, tessellation of polyphazed structures and Stienens model. Examples are given in both cases, such as UO 2 , Fe–Ag, TiC–Co, WC–Co, concrete…

Effect of powder processing on microstructure of zirconia during sintering

Abstract The effect of the processing route on both the sintering and mechanical properties of a stabilized zirconia was investigated. Zirconia samples prepared by dry pressing and by tape casting are compared from the point of view of microstructural evolution during thermal treatment and from the point of view of mechanical properties. Kinetics of densification and grain growth are studied by automatic image analysis. The greater homogeneity of the green state obtained by tape casting, in comparison with that obtained by pressing, leads to increased densification and grain growth rates, and to improved mechanical properties.

Liquid Phase Sintered Materials Modelling by Random Closed Sets

Three different probabilistic models are used in order to describe the microstructure of WC-Co hard metals. While a two-phase mosaic model and a dead leaves model with Poisson polyhedra as primary grains seem not adapted, a Boolean model with Poisson polyhedra fits very well the WC phase. The two parameters of this model allow us to estimate the thermodynamics parameters of the coarsening of the WC phase during annealing. It is also possible to evaluate the Euler-Poincare characteristic in R 3 , Nv (X), which cannot be measured by another means. Mechanical parameters are also correlated with the parameters of the Boolean model.

Roughness and

2014 In the case of absence of overlaps, roughness investigation can be studied from IR2 IR function analysis methods. These IR2 IR functions correspond to a true topography or a perspective representation. They can be quantitatively described directly from basic stereological parameters or after morphological transformations. Some examples in material science are given using scanning electron or confocal microscope images. Microsc. Microanal. Microstruct. 7 (1996) OCTOBER/DECEMBER 1996, PAGE 533 Classification Physics Abstracts 81.40.Np 07.05.Pj 81.70.Yp