Absolutely. The f'c of the concrete can be negatively affected. They have mneters to test for this and are used by structural engineers to test concrete walls after a large fire. I've seen this concern a lot in tilt-up warehouse fires.
Heat can affect concrete, although certainly not as much as most building materials. In a house fire, it would depend on where the concrete is located and what its function is. If you are talking about footings or slab on ground, I wouldn't worry about it.
The most common effect of heat/fire exposure on concrete is carbonation of the exposed surface. Take a couple of cores and have a petrographic examination done on the concrete.
Sometimes there has been little or no effect. One of the most common problems is that when the fire is extinguished with water, the sudden cooling cause the concrete to crack.
Concrete is fairly resistant to fire/thermal events. It takes a sustained elevated temperature (800C for 4+ hours)to serious degrade the integrity of the cement particle bond. Otherwise the effects are mostly physical cracking and carbonation of the surface.
Depends on the intensity and duration of the fire, the concrete may exhibit surface damages, such as cracks and spalls. If the surface damages have extended beyond the reinforcing, take some core samples at strategical locations sould be able to provide better indications.
Note that concrete repair over significant areas is difficult, and is not as reliable compared to the original undisturbed conditions. It could lead to weakened service performance, but may or may not be a vital concern on structural performance.
Each fire has its distinct characteristics, be prudent, exam and evaluate accordingly.
