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## Concrete and Fire Concrete of any age exposed to heavy fire is subject to spalling. This is the separation of chunks with explosive force caused by the expansion of water trapped in the concrete as the water turns to steam. Substantial chunks weighing 100lb or more can collapse as a result of exp...

## Concrete and Fire Concrete of any age exposed to heavy fire is subject to spalling. This is the separation of chunks with explosive force caused by the expansion of water trapped in the concrete as the water turns to steam. Substantial chunks weighing 100lb or more can collapse as a result of exposure to fire. Fortunately, it usually only occurs where there is direct exposure to flame. This reduces the danger to firefighters since it is unlikely that a firefighter would be in an area with a large quantity of open flame without an operating hose stream. Cooling the heated concrete reduces the chances of spalling but this can take tremendous quantities of water even after the flame has been darkened down. ## Upper vs Lower Floors The highest floors of a building are typically the last to be built. However, they are often the first to be rented because of the desirability of a view and the prestige associated with having offices on the top floor. The lower floors often remain unoccupied until a later date. This means they become storage areas for construction materials being used to finish the other floors, creating a heavy fire load. Construction codes allow these floors to remain unsprinklered even though the finished areas often with lighter fire loads require sprinklers. The feeling is that it would be more difficult to evacuate the higher floors, so sprinklers should be installed there. Firefighters should demand that sprinklers be operational on all floors below any occupied floors before allowing anyone to move in.