Joining new concrete to old

Its never a bad idea to chisel some slots and install some sort of metal ties in.

A 45 degree bevel on a step? - are you sure it's not just a kerbstone laid flat on it's back? Either way, you can't 'chamfer' concrete in this way, you are right to assume that it will crack up, the only way to stop this is to give it more depth, IE cut out a straight line with a grinder and chisel off an inch or two in depth, treat with neat PVA prior to concreting and scrape some slop into it.

Yes a chamfer would have been a better word; when I cast the steps some

Rob

I did something similar 10 years ago.....

Footings to my garage are a metre wider than the garage (raft foundation). My new block built shed was to be roughly 8' wide so needed footings that reached beyond the scope of the garage foundations. I got two great lengths of angle iron, bent them into large V shaps and bolted them to the side of the footings. Then I poured the concrete - angle iron was then submerged in concrete. OK, no 45 degree thing going on, but that new groundwork has never moved a milimeter in 10 years.

Hope that helps

Regards Paul