What happens when a Contractor breaches the contract?

Delay, workmanship, may be covered in General Conditions clauses, such as: GC 4.13 Rejected Work; GC 13.2 Delay by Contractor; GC 15.3 Termination; GC 23.1 Reimbursement for Wrongful Act or Neglect and others.

It is important to document all communications.

This situation may require legal advice...but check the GCs for sections relevant to the alleged breach