Microstructure of crushable expanded clay aggregates

The images show two different and complementary views of a mixture of Light Expanded Clay Aggregate (LECA) particles with size ranging between 0.25–1.0 mm. The upper-left is a SEM image showing a projected view of the particles, while the lower-left is a slice of a micro Computed Tomography (μCT) 3D reconstruction. The SEM image shows clearly the roughness and the asperities of the surface of the particles, while the X-ray tomography reveals the heterogeneity existing between different particles in terms of density (greyscale proportional to X-ray attenuation), grain shape and internal porosity. The μCT images on the right show the state of the material scanned at different levels of imposed one-dimensional deformation, indicating significant grain crushing. Particle scale phenomena can thus be tracked throughout compression giving an objective measurement of each particle’s life expectancy. A comparative analysis of the microstructural features of the material in its initial and degraded state was used to characterise the overall material compressibility and attempt to link it to the properties of individual grains [1].