Laserfiche WebLink
Table 3. Fire-resistance ratings of concrete <br />masonry walls1 <br /> in the concrete block mix. <br />Walls can be filled with grout, loose- <br />-33 or C- <br /> <br />. <br />If the aggregate blend is changed to 70/30 to produce <br /> architectural unit, the fire rating is decreased <br /> hours. <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />Application of the information in Tables 1 and 2 results <br />in the listing of concrete masonry wall fire ratings in <br />Table 3. <br /> <br />Fire-Resistance Rating Increases/Decreases <br />Finishes on concrete masonry walls can increase the fire- <br />resistance rating. If wall finishes are used see IBC Section <br />722.3.2. Contributions of plaster or gypsum wallboard shall <br />be determined from IBC Tables 722.2.1.4(1) and 722.2.1.4(2). <br /> <br />Additional masonry wythes can also increase the fire-resistance <br />rating of wall assemblies. Equation 7-7 of IBC section 722.3.3 <br />addresses multi-wythe masonry walls. <br /> <br />If the specified CMU density is increased, the proportions of <br />blended aggregates will vary from the 60/40 percentage <br />example used in Tables 2 and 3. There will be more heavy <br />weight aggregate and less lightweight aggregate in the <br />concrete mix and some ratings may decrease (see footnote 3 <br />in Table 3 above). <br /> <br />Fire Resistance Testing <br />It is important to remember that the term “fire-resistance <br />rating” is a legal term utilized by building codes to regulate <br />building construction. While the ratings are based upon a <br />standard fire test exposure, assemblies having the same <br />rating, but constructed with different materials, often perform <br />quite differently. <br /> <br /> <br /> <br />Fire-resistance rated wall assemblies are commonly evaluated <br />using ASTM Standard E-119 (ref. 7). The standard is used to <br />determine the wall’s hourly fire rating and to indicate its <br />expected durability during a fire. A wall tested according to <br />E-119 undergoes both fire exposure and water hose-stream <br />testing. <br /> <br />The hose-stream test provides a meaningful measure of <br />durability during a fire. It provides an indication of how well <br />the wall can endure fire exposure as well as falling debris, <br />pressure waves due to explosions, actual fire hose-streams <br />and other rough usage that often occurs during a real fire, <br />which can never be truly replicated in a laboratory test. <br /> <br />According to ASTM E-119, the hose-stream exposure test may <br />be performed in one of two ways. The basic test, typically <br />used for frame wall construction, permits the use of two <br />identical assemblies. The first one is subjected to the fire <br />exposure test to determine its hourly fire-resistance rating. <br />The second specimen is subjected to the fire exposure test <br />for only one half the recorded rating period (but not for more <br />than one hour). The second assembly is then removed and <br />hose-stream tested. The more rigorous optional E-119 test <br />method is commonly used for concrete masonry assemblies. <br />This second test method requires the hose-stream to be <br />applied to the same specimen that has undergone the full fire <br />exposure test. <br /> <br /> <br /> <br />Nominal Wall <br />Width (in.) <br />Block Wall Treatment <br /> <br /> <br />Empty or <br />Partial Filled <br />Wall2 <br /> <br /> <br />Solid Filled <br />Wall2 <br />4 1 hour 1 hour <br />6 1 hour 3 <br />8 2 hours 4 hours <br />10 2 hours 4 hours <br />12 3 hours 4 hours <br /> <br />Figure 2. Two-hour rated walls subjected to the hose- <br />stream test of ASTM E-119. <br /> <br />Concrete Masonry Wall <br /> <br /> <br />Gypsum Wall <br /> <br />