Quantification and characterization of microporosity by image processing, geometric measurement and statistical methods: Application on SEM images of clay materials

A series of image processing technologies and geometric measurement methods is introduced to quantify multiple scale microporosity in images. All the operations are non-destructive so as to ensure the accuracy of the results. With the application of these methods, various basic geometric parameters of the pores can be computed automatically in the computer, such as area, perimeter, direction etc. On the basis of these geometric parameters, probability entropy, probability distribution index and fractal dimension were introduced to describe the distribution of the three major characteristics of pore system, direction, area and form factor, respectively. Computer software developed on the basis of these methods was used to quantify the SEM images of clay samples during shear test. According to the quantification result, total pore area and average pore form factor reduce during the test. The variation of pore area and form factor is related to probability distribution index and fractal dimension, which indicates the variation of microstructures between pores. Error analysis shows that the deviation using the image processing is within 5%, and the deviations of statistical parameters are smaller in comparison with those of basic geometric parameters. The statistical methods are adapted to the quantification of 2D multiple scale objects. This paper offers a reliable basis for the quantification and characterization of microporosity by image processing.