of aggregates from the matrix material requires a detailed knowledge of the strength and break-up of compounds.

For the understanding of the strength and break-up process, the study of simple systems like spherical particles is essential. During the last decades several experimental and theoretical studies have been performed to understand the break-up of spherical bodies arising due to impact. The crack pattern of sand-cement spheres by a free fall impact was studied in Ref.  [@fra_pattern], which reports observations of meridian cracks, that divide the sphere into two nearly equal parts, and oblique cracks, which are straight like median cracks, but cut the sphere into two unequal pieces. The fracture of glass and plaster spheres by free fall impact and double impact (dynamic loading between two hard plates) have been carried out recently [@powder; @chau]. It was found that at the lowest impact velocities hertzian cone cracks (formed from a surface ring crack) are developed, whereas, at high velocities, oblique cracks propagate before meridian cracks form [@fra_glass]. This finding differs from the experimental results of Ref. [@fra_pattern], where it was found that with increasing impact energy, the number of meridian planes increases and oblique cracks start to develop.

Due to the 