Effect of Fire on Concrete.
Concrete is often used as a fire-proof building material, and as such is commonly considered a safe material for walls or foundations which may be built for that purpose. A few experiments will demonstrate its unreliability in this respect. Take a piece of dry and hardened concrete work, such as is used in walls or foundations, and break it into three parts or lumps, leave one in its original state and place the other two in the fire, where they should remain at a light red heat for five or fifteen minutes, according to size; them remove both pieces place one to cool naturally and the other in water to cool. When cold and removed, it will be found that the one naturally cooled will crumble easily and the one cooled in water will crack and fall apart with very slight pressure.
Some two years ago we had an experience with concrete walls, where the interior of a two-story building had been destroyed by lire. W e recommended that the walls be taken down and rebuilt; but it was decided to repair them. Where the fire was light, but little damage was done; but near the base of the walls, where the burning brands had fallen and the fire generated the greatest heat, wasa strip all round that had crumbled away, leaving the walls at this point only about half their original thickness. The most pronounced of the disintegrated concrete work was cut out and brick work built in; soon afterward the exterior portion of the walls showed signs of giving away,whereupon sections were cut out and built in with brick. As time passed, the walls in the other portions also began to show the disintegrating effect of the fire on the concrete work.
We wish more particularly to direct the attention of the officers of the various fire departments to the danger which may attend concrete work, especially where the basement or foundation has been built of such material and which in turn supports brick walls, three or more stories in height.
In many cases the concrete work is placed where fire and steam together will tend to weaken the support and in a moment, without warning, the walls may come tumbling down over the firemen, repeating the horrors frequently depicted by the press.—Architect and Builder.