ANFO
Low explosive anyway as that grain tower complex most likely wouldn’t have resisted the explosion and the shockwave would’ve traveled MUCH faster.
Here’s 100 tons of TNT.
https://www.youtube.com/watch?v=PgLzgdbfeJE&feature=youtu.be
You are correct. And if it were enhanced......it would have taken more down. No bomb maker with this much material would have left it as a low grade explosive. None.