I think what makes it look more like concrete are the sharp edges... most people associate soft more rounded edges with a mattress.
And, foam usually consists of lots of air, so you have small round "airbubbles" not the small long stripes seen in your shader...
Maybe you should try a soft spots node instead of the granite for your bump.

That's all I can think of right now...

Martin

Yesterday's the past, tomorrow's the future, but today is a gift. That's why it's called the present.