Cellular concrete with entrained porosity undergoes compaction produced by crushing of the cellular structure and subsequent densification of the material.

A compaction front is produced in the foam when the blast pressure amplitude is higher than the crushing strength.

There exists a critical length of cement foam, L_cr, such that when L > L_cr, the compaction wave diminishes before reaching the solid substrate and a rectangular stress pulse is transmitted at the target end.

When L < L_cr, the magnitude of the transmitted stress increases above the initial rectangular-shaped stress pulse.

If the length of the foam is significantly smaller than the required L_cr, the compaction in the material produces densification and the stress enhancement is higher than the applied blast pressure amplitude.