The behavior of sand-rubber mixtures is controlled by the mechanisms taking place at the grain scale. Here, we use a mixture of shredded tire and a silica sand with similar grain sizes to investigate granular behavior under one-dimensional compression. A mini-oedometer operating inside an X-ray scanner was used to assess the evolution of the microstructure under loading and unloading. New insights are presented on the development of the contact surfaces between sand and rubber and the evolution of the void space.