Fire can cause severe concrete damage because of shock heating. Concrete expands as it's heated. In the extreme heat of a fire, the outer layer will expand much more quickly than the inner portion, causing it to fracture and break away. This phenomenon is known as differential expansion. It can also occur in reverse when the fire is doused by fire hoses or a sprinkler system. In this case, hot concrete is cooled suddenly, causing the outer layer to shrink and break away.
TIP: Concrete is damaged by fire no matter what your claims representative or others may tell you. CARe will can provide documentation for homeowner use so damaged retaining walls and foundations are properly paid for and correctly replaced. Here is something to start with:
Routine monitoring and maintenance of concrete structures can extend service life and reduce long-term repair and maintenance costs.
By Michael J. Drerup, Project Engineer, Wiss, Janney, Elstner Associates, Inc., New York, New York, June 25, 2001
SOURCE: CARe, Inc. site - http://www.carehelp.org/disasters/fire.htm