I was planning on using 3/4 inch pvc conduit 90's to bring the 1/2 inch  tubing  into the mechanical room.  Is that necessary, since the tubing is in the concrete already?   I used them on the domestic lines in the slab and made for a nice job.  Looks like they would provide some protection during the finishing  of the concrete, but my carpenter just asked if they were necessary. 

The bends are to protect the tubing from shearing if, say, you kicked one after the pour. I would consider them necessary unless some other method of protection were used.