Beside looking terribly uncomfortable with all those edges, food bits can filter down between those large pieces. Then, the corys won't be able to get to it and it is apt to spoil and pollute the water.
Sand or fine gravel with rounded edges is much easier to manage and is safer for the corys.
I did keep a couple of corys in my betta tank that are now living in my big tank. The small tank has gravel and the big tank has a big sandy area at the front. The Corys seem much happier with the sand, i'm certain the barbels have grown since the have been in the big tank too.
Play sand is very inexpensive. You can get it at most any hardware supply. Once you have the sand, come back and someone will help you remove the gravel and add the sand.