That reinforced concrete serves to build chimneys and flues is proof of its fire-resisting quality. Concrete is a slow conductor of heat, and both it and steel have almost the same slight expansibility as temperatures rise, so that they remain together in a fire. Terra cotta, which expands much more than steel when heated, cracks off from the metal it was intended to protect, leaving it to bend or fuse in a blaze. Concrete, furthermore, behaves well when its temperature is suddenly lowered, as when a fireman dashes a stream of water upon it at a fire. No wonder, then, that the reinforced concrete is more and more in request in cities as the material for buildings rising higher and standing more thickly on the ground than did buildings of old. In the great fire in San Francisco, April, 1906, reinforced concrete withstood extreme temperatures much better than any other material. It will be largely used in rebuilding the city.
Column form, Ingalls Building, Cincinnati. A, A, yokes. B, B, spacing pieces. From “Reinforced Concrete.” A. W. Buel and C. S. Hill. Copyright, Engineering News Publishing Co., New York, 1904.
Resistance to Fire and Rust.
Frequently the question is asked, Is the steel in reinforced concrete liable to corrosion, so that its walls are likely to become weak and insecure after a few years? With careful planning and faithful workmanship the results prove to be worthy of confidence. Professor Charles L. Norton of Boston has taken steel, clean and in all stages of corrosion, and embedded it in stone and cinder concrete, wet and dry mixtures, in carbon dioxide and sulphurous gases; other specimens were intermittently exposed to steam, hot water, and moist air for one to three months. Duly protected by an inch or more of sound concrete the steel was absolutely unchanged while naked steel vanished into streaks of rust. Mr. Ransome says that in tearing up a stretch of sidewalk in Bowling Green Park, New York, in use twenty years, some embedded steel rods were found in perfect condition. The Turner Construction Company, of New York, exposed concrete blocks in which steel bars were embedded, and laid them on a beach at low tide where they were covered by salt water three or four hours every day; after nine months’ exposure the blocks were broken disclosing the bars free from rust. Professor Spencer B. Newberry records that a water main at Grenoble, France, built on the Monier system, twelve inches in diameter, eighteen inches thick, containing a framework of 1⁄16 and 1⁄4 inch steel rods, was found perfectly free from rust after fifteen years’ service in damp ground. He also states that a retaining wall of reinforced concrete in Berlin was examined after eleven years’ use and the metal found uncorroded, except in some cases where the rods were only 0.3 or 0.4 inch from the surface.
Section of chimney at Los Angeles, Cal.
Coignet netting and hook.
