I am planning to pour an L-shaped concrete patio approx. 30' x 20' in our back yard that will attach to our existing foundation in Texas. (picture a 30' x 20' rectangle with a 12' x 12' square out of it which represents the existing home). I have been told two different things regarding pinning it to the existing foundation. I am already planning to epoxy rebar into the existing foundation to prevent vertical movement of the patio. I'm also planning to place fiber expansion strips between the patio and existing foundation. Some suggest that I use the rebar caps that will prevent the new concrete from bonding to the rebar in order to allow some horizontal movement in the new slab. ...but the L shape means that the rebar will attach to the new slab in two different directions, which would tend to prevent this horizontal movement anyway. Others say to simply allow the rebar from the existing foundation to bond into the new concrete. If I would do this, I'm not certain what the purpose of the expansion strips surrounding the existing foundation would accomplish other than to provide a cavity to place SL-1 sealer and give a more finished transition between the house and patio. The rebar I am referring to above is simply the 2' foot sections of #6 that are epoxied to the house. The remainder of the new slab will have rebar placed in a conventional manner.
A second question involves the placing of some concrete pillars around the outside of the patio. On someone's advice, I've already placed (3) 9" diameter by 3-4 feet deep concrete pillars with vertical rebar reinforcement at the perimeter of the planned pour where the slab will be the weakest. The top of the pillar is at the bottom of the planned slab. The question involves the rebar that is currently sticking up from each pillar. If I allow this rebar to stay, it will bond into the new concrete (it will be cut 2" below the top of the new slab). I am wondering if this is a bad idea as it will lock the patio into place horizontally as well as vertically - could this promote cracking by preventing all temperature related movement?
I am planning to pour the slab 5" thick with control joints cut 1" deep with hand jointers during the pour in both directions on about 2' centers to mimic large tiles and to provide plenty of area for controlled cracking. Our area in Texas has very little freezing, but it does have plenty of expansive clay soil. All topsoil was already removed from the new pour, and a layer of 6" or so of crushed concrete was laid for a base. The new slab does slope away from the home in both directions. The slab will eventually be acid stained.
Thanks for any advice in advance.
Jeff