Fire Rated Concrete Wall Thickness

The fire resistance ratings of precast concrete wall panels consisting of a layer of foam plastic insulation sandwiched between two wythes of concrete shall be permitted to be determined by use of equation 7 4.

Fire rated concrete wall thickness.

It is calculated by multiplying the actual thickness by the percent of solids. Moreover the contribution of foam plastic fire resistance is zero if its thickness is less than 25 mm. For example for an 8 in. 203 mm limestone aggregate concrete masonry wall with a maximum control joint width of in.

The equivalent thickness is the theoretical thickness of the block if all the concrete was molded into a solid unit. Another factor to be considered in complying with fire resistive requirements is the minimum thickness of concrete cover for the reinforcement. 25 mm thickness measured perpendicular to the face of the wall of ceramic fiber in the joint can be used in walls with fire resistance ratings up to 3 hours while a 2 in. Aci tms 216 1 14 code requirements for determining fire resistance of concrete and masonry construction assemblies lists the minimum equivalent thickness of single layer concrete walls to meet fire resistance ratings ranging from 1 to 4 hours see table on following page.

Walls composed of hollow concrete masonry units having a nominal thickness of 8 inches or greater and having a fire resistance rating of at least 2 hours shall be classified as 4 hours when the hollow spaces are completely filled with perlite or vermiculite grout or a material such as expanded slag clay shale slate or sand. These values are for solid walls or slabs. If the foam plastic thickness is not smaller than 25 mm r n0 59 in equation 6 is equal to 0 22. Foam plastic insulation with a total thickness of less than 1 inch 25 mm shall be disregarded.

The fire resistance rating of concrete masonry walls depends on the type of aggregate used in the units. The concrete protection specified in aci 318 for cast in place concrete will generally equal or exceed the aci 216 1 minimum cover requirements but there are a few exceptions at the higher fire ratings. A 2 hour rating can be achieved by a wall with an equivalent thickness of as little as 3 1 5 inches when expanded slag or pumice is used or 4 1 2 inches when siliceous gravel is used as the aggregate. 13 mm a 1 in.

Fire rating fire resistance of concrete masonry units is determined by the equivalent thickness of the block and the type of aggregate. Fire resistance is controlled by both the physical and thermal properties of the structural element.