ADVANTAGES OF REINFORCED CONCRETE Reinforced concrete possesses many advan tages that other building materials do not, and these have led to its rapid growth as a standard for many types of structures. The chief advan tages that reinforced concrete has are as follows: Its moderate cost of construction—less than that of steel, and only slightly greater than that of wood.
Its remarkable fire-resisting qualities, that have been shown in many instances.
Its strength and its capacity for resisting shock, due to the monolithic or one-piece nature of the structure.
Its freedom from rotting, to which wood structures are subject in course of time.
Protection afforded by the concrete to the reinforcing steel, which would corrode rapidly if left exposed.
Its capacity for resisting the action of many chemical compounds that would soon destroy structures made of wood or steel.
Reinforced concrete's low first cost has led to its use in preference to masonry and steel con struction. While wood structures are cheaper than concrete, the latter are to be preferred on account of their superior fireproof qualities and their freedom from decay caused by rot and the attacks of vermin and insects. Fire insurance rates for reinforced concrete buildings are only about half those for wooden buildings of the type known as "slow-burning mill construction." The cost of repairs is much less, and no painting is required to preserve concrete structures sub jected to ordinary usage.
Concrete structures may be erected with a rapidity and ease that are astonishing. Entire buildings have been erected in the time ordi narily taken to design and form into a whole the structural metal work for a similar building in steel.
Concrete has the power to resist the action of many chemical compounds that would cause the ultimate destruction of either wood or steel structures. The failure of wood construction is caused by the decay of the timber when exposed to the action of air combined with moisture or chemical acids. In order to preserve wood from this action, it must be covered with some resist ing substance, such as sheet lead. This is expen sive on account of the high first cost, and the cost of the lead burning required to make tight joints. This form of construction is not entirely
satisfactory, as the lead, when exposed to the action of the gases, becomes brittle and soon cracks, allowing the chemical material to escape or become diluted and mixed with foreign substances.
Steel, when used for tanks or other struc tures containing chemical compounds, will cor rode very rapidly, and must therefore be pro tected by lead or some other substance that will entirely prevent the steel and the chemical from contact. In many cases this protection may be secured by a covering of concrete from one to three inches thick. If the steel be used to resist tensile stresses only, and the concrete to resist compression, the quantity of steel will be re duced, and the cost of construction with it. The resulting reinforced concrete structure will be equally strong and better able to resist corro-, sion. This method would require no extra steel to be added to prevent corrosion, as is now com mon practice in the design of steel structures in chemical plants.
Gases passing through a chimney from a steam boiler contain sulphur and other impuri ties which will act upon a steel stack in contact with them. Steel stacks as a consequence have a very short life. The use of reinforced concrete stacks is rapidly growing, because of their low first cost and their ability in resisting the action of the stack gases. An inner shell separated from the outer wall of the stack by an air space, should be provided to take care of the expansion caused by the heat of the stack gases.
It has been demonstrated by numerous ex periments that concrete will protect steel from corrosion. Some tests by Professor C. L. Nor ton demonstrating this, were made by embed ding specimens of steel, clean, as well as in all stages of corrosion, in stone and cinder concrete made with both wet and dry mixtures; and then these samples were exposed to moisture, carbon dioxide, and sulphurous gases, for periods of time varying from one to three months. The steel, where unprotected, rusted completely away; but when protected by an inch or more of sound concrete, was not affected.