Remove the old crumbly stuff and using cement patching compound, mix up according to the bag, and patch, wetting the old cement first. You may need to make a dam around what you are repairing with some plywood. In my experience, the prep is the most important-- make up forms for the border and it becomes more like filling a cake pan than trying to be a sculptor.
I agree with Roxaneg - in particular about doing the prep work. Take the time to build those forms because, in the end it will look so much better and it will last longer.
Remove the old crumbly stuff and using cement patching compound, mix up according to the bag, and patch, wetting the old cement first. You may need to make a dam around what you are repairing with some plywood. In my experience, the prep is the most important-- make up forms for the border and it becomes more like filling a cake pan than trying to be a sculptor.
I agree with Roxaneg - in particular about doing the prep work. Take the time to build those forms because, in the end it will look so much better and it will last longer.
Good luck!
Have fun!