Hexogen is the active principle behind military explosive such as RDX and C4.
A very powerful explosive, also known as cyclonite, obtained from methenamine, which also played a role
in the 3/11 case.
It develops a very sharp shock wave, that causes metal sheets, such as the ones of the walls of a train carriage, to be rather cut, not teared appart.
This kind of damage was observed by the chief TEDAX (Technicians of Explosive Deactivation) at Atocha station.
Military explosive have to develop a high brisance in order to bust reinforced structures such as concrete ones, whilst commercial ones, such as the dynamites, like Goma-2 ECO, usually exhibit lower brisance in order to be employed in quarrying, that is, to break the rock in big pieces instead of fragmenting it.