Characterization of EPS lightweight concrete microstructure by X-ray tomography with consideration of thermal variations

This paper presents a refined morphological and thermal characterization of a polystyrene-based mortar using X-ray micro-tomography where a dedicated X-ray scanning and volumetric processing protocol was developed. All the reconstructed volumes had a mean voxel size between 10 and 20 μm. In complementary procedure, the interactions between the different phases of the material have been investigated, by observing the interface using scanning electron microscopy (SEM). After a set of volumetric analysis, the obtained representative elementary volume (REV) was 10 × 10 × 10 mm3. The microstructure (porosity, pore diameter and interface, etc.) has been studied by 3D image analysis. The material's response to thermal solicitations at a local scale has also been examined, by observing its microstructural variations under thermal loads using an optical microscope. The micro-tomographic results allow us to assess a representative elementary volume for the polystyrene mortar, to evaluate its total porosity using two different approaches, and to have access to the pore size distribution. The SEM images show a good adherence between the two phases of the material, and the microscopic tracing under thermal solicitations indicates possible alterations of the beads from a temperature of 100 °C, unlike the literature results.