This dataset contains two micro X-ray Computed Tomography (micro-XRCT) data sets from scans of the identical cylindrical sample (diameter 80 mm; unloaded height 80 mm) under different uniaxial compression loads. The sample consists of monodisperse soft (rubber) and stiff (glass) particles mixture. Both particles have an identical diameter of 4 mm. The volume fraction of the rubber particles is 50 %. The scan was performed in a low X-ray absorbing transparent oedometer cell with an integrated pair of P-wave ultrasonic transducers to determine in situ the sample stiffness based on wave propagation velocity measurements. On both sides, the wave travels through a 10 mm long Poly (methyl methacrylate) (PMMA) pre-run and after-run section, before and after the wave enters and leaves the sample.

The prepared sample inside the oedometer cell was uniaxially compressed in axial direction in subsequent force increments from F_stat. = 200 N to F_stat. = 1000 N (force-controlled) using a Universal Testing Machine (UTM) integrated into the XRCT system. At each force level, the system was relaxed for some time at the defined force to compensate the creep behavior of the soft particles. Subsequently, ultrasonic wave propagation measurements were performed at five different load levels, F_stat. = {200, 400, 600, 800, 1000} N. micro-XRCT scans were acquired in situ at F_stat. = {400, 800} N. For this, it was switched from force-controlled to displacement-controlled to avoid creeping and an eventual movement of the particles during the imaging.

In this data set, the reconstructed 3d volumes ("mixture_nu0.5_F400N_reconstructed.tar.gz" and "mixture_nu0.5_F800N_reconstructed.tar.gz"), as well as the projection images ("mixture_nu0.5_F400N_projections.tar.gz" and "mixture_nu0.5_F800N_projections.tar.gz") for both preloads are given. The raw ultrasonic measurement data (transducer signals over time) is provided for all five preloads ("mixture_nu0.5_ultrasonic_data.tar.gz"), before and after the force-controlled relaxation, as an averaged signal of a stack of 32 signals. The file "mixture_nu0.5_utm_data.csv" contains the measured axial force and displacement from the UTM during the whole experiment. Based on the measured displacement of the UTM, the current mixture length was determined. In the file “mixture_nu0.5_P-wave_moduli.csv” the final calculated P-wave moduli for the different preload levels are contained.

Ruf, M. and Taghizadeh, K. contributed equally.