jerry, This is a no brainer. It sounds as if the concrete contractor has assumed responsibility by trying to take care of the problem. This is a go0od example of why you want to make sure that only licensed contractors work in your home.
There is a state license bond that must be carried by all licensed contractors. In California, plumbing contractors bond is $7500.00. Contact your state license board to find out the correct way for you to file a complaint. If the contractors insurance does not take care of it you would have a claim against the bond.Do it quickly for time could be an issue.
The Local Plumber
Tustin, California http://www.TheLocalPlumber.com