Last week before the St. Pete Indy race here in Florida an oil tanker crashed killing the 47yr old driver on the freeway overpass. The fire was reported to have exposed the original frame. Do u feel it was bad building codes that were passed long ago, bypassed? Did the cement melt?In need of a brainiac please.TY
The cement didn't melt. It heated up, which caused it to expand. Since it had nowhere to expand TO (the concrete itself was hot, concrete around it was not, high expansion, no place to go), it crumbled. If you go to the overpass site now, you'll see a sizable pile of scorched black cement dust and rubble below the fire site.
The heat from the fire caused the concrete encasement of the steel to expand, crack and fall off, exposing the frame. I doubt the temperatures reached were high enough to melt the concrete, you'd be talking volcano like temperatures.
Cement ... more accurately , concrete does not melt. During a fire such as you describe, the concrete will spall which means that it will break into chunks. These chunks will fall away from the reinforcing network of re-bar and exposing it to the heat of the fire. The expanding re-bar will add stress as well as serving to conduct the heat to deeper within the structure eventually resulting in failure and collapse.
