I drilled 4 10" dia post holes in my concrete patio to build a pergola. I have 6"x6" posts in the hole. I dry packed concrete into the holes with the posts up to about 4" below the surface of the concrete patio. I bought the concrete dye that matches my patio and was planning on mixing up wet concrete with the dye and filling in the holes, making a slight crown against the posts for water drainage. Do I need an expansion barrier between the new concrete and the existing concrete patio? Or will any expansion push into the relatively soft wood of the post?