Anyone know if there are masonry grinding wheels for angle grinders that would be around 10" or so? This would be the depressed style. The only ones I've been able to find max out at 7",
For that I'd probably use a big coarse stone cup wheel for stock removal and finish flat with a standard coarse 9" disc. I did exactly that forty years ago on some cast entry steps I was fitting with new cast custom treads.
Well tell ya what packard. Pretty good chance I’ve spent a few hundred hours on my knees periodically over the last 40yrs making dust. Trust me OP, don’t bring a butter knife to this gun fight. Unless you’re dealing with a high psi mix, standard mortar is pretty soft and easy to grind off. Get a diamond wheel and be done with it in short order.