Bricks, Masonry, Asphalt and Concrete - Cosmetic patch work

I have a concrete slab that is 3 years old and when they poured it one of the forms on the end had a belly so the end of the slab looks slightly rounded. In order to make it square, I would have to add 2-1/2" to one corner and taper it down to nil about 3 feet from the corner. This is totally cosmetic and will have zero weight on it. I have enough room for most of it to drill and install some 3/8 rod to help hold it.

What is the best mix for hand trialing this, and do you have any other recomendations ie, primer or bonding agent?

Clean the existing pad well where new concrete will come in contact-scrub with a stiff wire brush and hose off.As you said,drill some holes and hammer in some lengths of rebar sticking out a bit.Acryl 60 is a great bonder,as well as Thorobond.You can even slide some wire lath in your new pour.Your other option is to square off the belly by sawing it off with a cut off saw/diamond blade combo if the edge won't be seen.