A Computational, Multi-Physical Assessment of Commercial Structures Subjected to Fire

In commercial construction, where concrete masonry units have certain fire rating requirements, there are two methods that may be used. The first method (and least used) is to have the Underwriters Laboratories (UL) review in person the manufacture of the block, including the mixing of the aggregates. When the blocks are manufactured under the UL’s inspection, the block are then stamped and approved for specified fire rating. The next method (and most used) is to determine the equivalent thickness of the unit where the volume of the masonry unit is divided by the area of the exposed face. Depending on the type of aggregate used, a four hour fire rating may vary from an equivalent thickness of 6.7” for siliceous gravel to 4.7” for Pumice or expanded slag.