You used some type of Deicer on them and the acid broke down the concrete.

Remove any loose pieces.

It is easy enough to buy some plywood to set the risers and start at the bottom step mix some cement trowel it out and flat. Wait a couple days and go one more step up. Or even easier hire a pro they will form out and you will be able to use the steps the next day. It would probaly cost a lot less then a single lawsuit if someone slipped on your new concrete steps and blamed you.