Fire effects for clay tile or concrete masonry

[SperlingPE]

I have been tasked with evaluating a building that had a fire. The fire was confined to the interior of the building and a relatively small space. The building construction is steel columns, beams, and (roof) joists. There are also masonry bearing walls. The construction of the walls is unknown (until I can inspect). I suspect that the wall are clay tile (1956 construction). I do not know the nature of the fire (what was burned)at this time. Does anybody have information regarding what affect fire/heat has on the clay tile (or concrete masonry)?

 

[adk]

I have helped to evaluate a small residential structure damaged by fire, one w/ CMU walls. I don't remember any cracking or spalling, which is the main issue that I know of with concrete and fire. Concrete I believe always retains a certain amount of moisture, and if superheated that water expands into steam and causes stress cracks, or spalling.

HTH
adk

 

[jheidt2543]

The first thing I would check are the steel deck, the joist and the structural beams. They frame the roof and would usually suffer the highest tempertures first. The roof deck can be easily replaced so, it is not major concern other than wanting to keep the building watertight.

If the joist and beams are still straight and not deformed at all, then it is likely the fire was not hot enough to do any damage to them. By checking the extent of paint damage on the steel, a fire investigator can tell the approximate temperature of the fire. Steel will begin to loose some of its strength at tempertures in the range of 700 - 800 degrees, but collapse is a function of both fire duration and loading.

The next step is to check the bearing points where the steel joist and beams bear on the masonry wall. The steel members may not have been heated enough to cause damage to themselves, but they could have expanded enough to push on the wall. Check for wall cracks around the joist plates and beam plates. New cracks should show through the soot on the inside of the wall. A really hot fire will damage the masonry, usually the mortar joints first. The joints will crack and turn powdery. The only solution is replacement.

Here are some temperature indicators of how hot a fire has been as determined by material melting points in degress (F):

Polyethene 230 - 250 F
Lead 620 F
Aluminum Alloys 900 - 1200 F
Glass softens 1100 - 1350 F
Copper 1980 F

This is a start, I'm sure your local fire department would have much of this information.

 

[Ron]

SperlingPE...jheidt's comments are on target. Structural clay tile is not usually damaged by the heat from a fire, but the sudden cooling on extinguishing can cause significant cracking problems. Additionally, the mortar is greatly affected.

As jheidt said, if the steel didn't get hot enough to deform, the rest is probably OK. For concrete, the temperature has to be at about 600 to 800F for a sustained period of several hours to actually break down the cementitious structure. You can get carbonation to depths of 1/8 to 1/4 inch, at lower temperatures, which will degrade the surface but not greatly affect the overall integrity.