If the work was done the surface may be a little weak. You can have the contractor sand blast the surface to remove any loose areas of concrete.
If you are unsure of the strength of the concrete you can have it tested by a Civil Engineer who will core a sample of the concrete then break it in his lab. The test should be done after 28 days have elapsed. This is the time needed for a concrete to get to its specified stength (Usually). This will tell you if the strength has been compromised.