Please Help with Blender/Unity issue

So I created some bricks in Blender. I used the sculpting tool to sculpt it down a bit, and then duplicated it over and over to make a brick wall. When I import it into Unity as an FBX I can lay my walls in place. After a few walls are laid down it slows down and eventually I get a out of memory error. No I think its either my pig of a computer…I3 with 4 gb ram, or I need to somehow dumb down my bricks a bit. If the latter is the case, does anyone know any tricks to help with this?

Thank you in advance.

Sculpting relies on having a relatively high poly count so not really suitable directly for use in a game engine.Decimate modifier ?

You could also look at baking (Render / Bake panel) bump or normal maps to use with a low poly object to fake the high details