- Author
-
Mitchell, N. D.
- Title
- Fire Tests of Gunite Slabs and Partitions.
- Coporate
- National Bureau of Standards, Washington, DC
- Report
-
BMS 131
May 12, 1952
13 p.
- Keywords
-
slabs (members)
|
fire tests
|
partitions
|
concretes
|
fire endurance tests
|
aggregates
|
sand
|
asbestos
|
sawdust
|
thermal conductivity
- Abstract
- Eight slabs and four partitions made with gunite concrete on wire-fabric reinforcement were subjected to fire-endurance tests at the National Bureau of Standards. The slabs were made with aggregates composed of sand and wood sawdust, the sawdust ranging from 0 to 50 percent by volume of the aggregate. The aggregate for two partitions was sand, a third had a minor amount of asbestos added, and that of the fourth consisted of equal volumes of sand and sawdust. Fire-endurance limits for the slabs increased almost linearly with increased percentages of sawdust incorporated into the mix. Partitions made with sand aggregate only in the concrete or with the addition of a small amount of asbestos fiber to the concrete showed early failure by spalling and holing through. The explosive violence of the disruptions suggested the presence of entrapped water in the dense concrete. A partition made with a concrete having equal volumes of sawdust and sand as aggregates did not spall and failed by a limiting 325 deg F rise of temperature at a single point on the unexposed side only 70 min of fire exposure, whereas the partitions having asbestos and sand or sand only as the aggregate reached fire-endurance limits through explosive spalling in 16 to 26 min. Subsequent to the fire-endurance test, the partition with sawdust successfully withstood the application of the hose-stream test. The effect of the sawdust is to lower the thermal conductivity of the concrete and increase its porosity, thus making easier the escape of moisture in the form of vapor.