Show severe tests give top rating to new type of concrete block CHICAGO A new type concrete masonry block has received a top rating after severe fire water and pressure tests in the underwriters laboratories here the eight inch thick wall was given a 3 hour fire classification a rating of half an hour longer than any previous eight inch wall of concrete masonry units has been able to secure A laboratory inferno was the testing ground tor for the new hollow building block A specially designed furnace was built which burned 10 cubic feet of gas an hour as much as a small city for tour four hours the 11 by 10 foot experimental wall of blocks was subjected to fire in the first five minutes the wall reached a temperature pera ture of 1000 degrees fahrenheit at the end of one hour the exposed face was up to 1700 degrees at two hours 1850 degrees and at the completion of the test a tempera temperature ture of 2000 degrees fahrenheit was recorded wall remained intact all this while great hydraulic jacks were pushing down on ali the wall with a pressure averaging pounds to the square inch at the end of the four hour ordeal the wall was removed from the fire blast and its incandescent face was washed with a stream of cold water from a fire hose under a water pressure of 45 pounds to the square inch great clouds of steam obscured the wall snapping and crackling noises were heard as the wall underwent its rapid cooling and contraction the wall remained intact after this whole series of destructive actions architects and engineers examining it later expressed amazement at the slight effects of the severe treatment temperatures recorded on the unexposed surface of the wall during the tests resulted in the prized 3 hour classification this rating can be increased to a tour four hour classification fi when such walls are surfaced with three quarters of an inch of gypsum plaster greater fire protection at a low lower cost is the objective of the research which developed the building blocks |