I am turning part of my carport into a new living room. I am going to pour a concrete slab about 4 inches thick over the existing carport floor which is a concrete slab. The existing slab has a few cracks, the largest of which is about an 1/8in. Wide and raised about an 1/8in. What would be the best way to go about putting in this new slab? Should I cover the old slab with plastic to prevent the two slabs from bonding, or should I grind down the raised crack and fill all the cracks in? Or is there a better approach? Any help would be greatly appreciated, thank you!