One option is to get a bag of sand mix, which is like concrete mix, but with no aggregate in it. The I'd mix it up to a fairly stiff consistency so it wouldn't sag in the type of vertical application shown in your photo. Since it is simply a sand-concrete mix, you should be able to get a fairly decent surface on the patch by gentle troweling. Remember to wet the old concrete first so that the new material will form a decent bond with the old concrete. You'll probably have to keep an eye on it as it sets up and re-trowel lightly if you are getting too much creep or sag. If it's too hard to do an outside corner like that at one go, place a small board up against one side as a guide and fill in the open face. Then, when the first side has set up, fill in with sand mix on the other surface. Alternatively, patch both faces, but don't try to get it perfect in one shot: underfill, let it set up, then add a second patch on top of that to bring it flush.

If you want to go with a higher quality product that may be easier for you to work with, get a bag of Ardex CP (concrete patch). It applies with a nice, creamy consistency, and sets up pretty quickly. You may have to go to a masonry supply store to find it.

Here is a link that might be useful: Ardex CP

Concrete-based patching materials will be the low cost option. A bonding agent will help with adhesion. Using grout for ceramic tile with bonding agent might produce smoother results. For the smallest holes and for best bond, epoxy would work well but is not low cost by any means. Once the patch sets or dries, light sanding with 120 grit flexible disc should smooth things even more. The disc will dull almost immediately but can be used as long as it is effective

Just to highlight on kudzu9's information.

Make sure you wet area b/4 applying. You don't need to flood the area, a pump up sprayer or a hand held bottle with sprayer should do you just fine. It does have to be wet, this is very important.

Make sure it's a stiff consistency. You know how you'd take a bucket of sand at the beach, fill it up, turn it over and pull the bucket off. It doesn't have to be that stiff, but almost. It's called the slump. You can take a paper cup and fill it or when you mix a small batch in a 5 gal bucket, you can see how stiff it is in the bucket.

Don't try to do it in one shot.

Here's a small patch job on a front stoop. The block was disintegrated.

I used surface bonding cement. Readily available at your local box store. It would be rather expensive to do a really large area with this stuff, but it fit the budget for the task at hand.

Here is a link that might be useful: Surface bonding cement

This post was edited by Roof35 on Sat, Oct 11, 14 at 20:40