Let me draw you a picture:
An typical untreated room (not concrete walls: gypsum):
As you can see, the lows partially passes through compared to if the walls hade been solid, but still, the longest decay times are still not in the high frequency range. If solid walls, the decay times usually increases for lower frequencies all the way down to the first mode:
Now, even if looking at the first decay plot: What do you think would be the result if we where to go nuts with this: 