85
3220.044
Copeland, R.E.
Concrete Products
Article
Maclean Hunter Publication
1964
November, Vol. 67, No. 11
38-42
N
The procedure generally used in fire testing building materials is prescribed in “Methods of Fire Tests of Building Constructions and Materials” (Designation E119) of the American Society for Testing and Materials. Only the principal details of fire tests of walls will be given here.1. The test wall must be representative of the construction for which fire resistance classification (rating) is desired. It must be aged and dried as specified.
2. The area exposed to fire must be not less than 100 sq. ft. with neither dimension less than 9 ft.
3. Load-bearing walls are subjected to a superimposed vertical load, approximating the design load, during the fire endurance and hose stream tests. Immediately after fire exposure the wall is subjected to the full force of a fire hose stream. Following a cooling period the superimposed load is increased to twice the design load.
4. Non-load bearing walls are not loaded externally but are built with all edges tight against a restraining frame. Such walls which classify for fire ratings of one hour or more also are subjected to the hose stream test.
5. The test wall is placed in the open side of a gas-fired furnace so that one face is exposed directly to the flames and heat from a large number of uniformly spaced burners. The opposite face is exposed to the air of the laboratory.
6. The furnace temperature is controlled to conform within specified tolerances to the standard time-temperature curve shown in Fig. 1.
7. End point temperatures (conclusion of fire test) are attained when the heat transmission through the wall is sufficient to cause an average temperature rise on the unexposed; surface of 250°F. above the initial temperature. In addition, the maximum temperature rise at any point on the unexposed surface may be limited to 325°F.
8. Failure is denoted by excessive temperature rise on the unexposed face, by passage of flame or gases hot enough to ignite cotton waste, or by collapse during fire exposure of any other phase of the required procedure such as the hose stream or double load tests.
Usually, the wall is exposed to fire until the limiting temperature on the exposed surface is attained or other failure occurs. However, in some tests the fire exposure period may be no longer than the desired rating, for example, 3 hours, even though the unexposed surface temperature is well below the limiting value.
Fire endurance periods for test walls are reported to the nearest minute, for example, 3 hours/31 minutes. Ratings, however, are expressed in coarses increments, a half-hour being about the smallest increment for ratings to 2 hours and 1 hour increments for ratings over 2 hours. That is, a fire endurance period of 3 hours/31 minutes would qualify the wall for a 3 hour rating.