January i, 1910.] 



THE INDIA RUBBER WORLD 



121 



lines where there is a possibility of dampness coming in direct 

 contact with the insulation. 



Paper, fiber, cambric, and vulcanized oil have all been used 

 where cheapness in first cost is desired, but in all cases where 

 engineers are asked their opinion and where the United States 

 government installs lines for communication or defense, rubber 

 is always specified. 



Scientific investigation of the physical and chemical qualities 

 of india-rubber applied as insulating media have been gven very 

 close study during the past few years. As an English writer 

 states, india-rubber is a most curious material to deal with in 

 many ways ; it alters its physical properties so enormously under 

 different conditions. When vulcanized its physical properties 

 are almost exactly the reverse of what they are when unvul- 

 canized. In its original state it is elastic ; when compounded or 

 mixed it is non-elastic, but when cured or vulcanized it becomes 

 more elastic than ever. 



Effect of Sulphur upon Coppf.r. 



The vulcanizing process, which of necessity calls for the use 

 of sulphur, naturally has a deleterious effect on the copper con- 

 ductor. Many plans have been suggested and are in use whereby 

 pure rubber or unvulcanized mixtures are placed next to the 

 conductor, the vulcanized protection being a second layer sur- 

 rounding the first. Even under these conditions the sulphur has 



been known to attack the conductor. An English chemist finding 

 that bromine, iodine, and chlorine, instead of oxidizing india- 

 rubber in contact with water, produced an altogether different 

 effect, endeavored to turn this to account in the manufacture of 

 cable core. By his process the conductor was covered with two 

 coatings of india-rubber which were first made to adhere in 

 boiling water and afterwards run through a solution of iodine. 

 The rubber treated in this manner was said to withstand a con- 

 siderable amount of heat without deteriorating. It also resists 

 the action of air and that of ordinary solvents. 



This method of applying insulation containing no sulphur 

 does not attack the copper and has therefore been recommended 

 for special work. The compound is said to retain a permanent 

 elongation like copper when subjected to tension, so that the 

 conductor would keep central when the strain on the core is 

 released. The elastic qualities of india-rubber are also improved 

 by the above treatment. 



Owing to the enormous variations in the nature of vulcanized 

 india-rubber as manufactured by various mixings and methods 

 of treatment, it is difficult to give any definite physical, mechanical 

 or electrical data for actual tests, but by specifying certain 

 amounts of thoroughly dried high grade gums, specifications can 

 be drawn of sufficient accuracy to meet the electrical conditions 

 desired. 



Reinforced Concrete in Factory Construction. 



By John O. Be Wolf. 



[N the growth and improvements in factory construction since 



1 the birth of The India Rubber World, twenty years ago, 

 the most radical departures from previous methods, and the 

 ones that are at present attracting the most attention, are those 

 due to the introduction of reinforced concrete into structural 

 work. This is becoming so general in its application and is 

 especially suited to so many purposes that it is now receiving 

 the most careful study of builders and engineers and has awak- 

 ened great interest among mill owners. 



Reinforced concrete is the name generally applied, in the 

 United States, to concrete that has been strengthened by em- 

 bedding in it steel or iron, either in rods or other forms. It is 

 sometimes called armored concrete, ferro-concrete, and concrete 

 steel; in France it is known as beton armc. Ordinary concrete 

 is a combination in proper proportions of cement, sand, and 

 broken stone, gravel or other suitable "aggregate." After it is 

 thoroughly set it forms a mass as hard as stone. This is ad- 

 mirably adapted to resist pressure, but is weak in resistance to 

 tensile strains. By embedding steel at the proper places in the 

 concrete it resists the tensile stresses and the concrete resists 

 the compression. All embedded metal does not constitute rein- 

 forcement ; a beam surrounded by concrete is simply protected 

 or fireproofed by the concrete, as the beam bears all the stresses. 

 It is not reinforced concrete unless the metal is so placed as to 

 bear those stresses which the concrete cannot resist unaided. 



The invention of reinforced concrete is generally attributed 

 to J. Monier, a French gardener, who about 1868 experimented 

 along this line and first successfully applied it to the construction 

 of large flower pots, cisterns, pipes, and the like. From this 

 beginning has grown the present industry, which in many ways 

 is radically changing building construction. Progress was slow 

 at first, but as soon as the Monier system of construction became 

 known others were brought out. differing only in the style of 

 reinforcement and the methods of construction. 



The first American patent issued in connection with this new 

 kind of construction was in 1878. to Thaddeus Hyatt. He 

 patented a special form of reinforcing rod with obstructions on 

 it to prevent its slipping when in the concrete. About this time 

 Ernest L. Ransome was working on concrete construction and 



invented the square twisted reinforcing bar, which he patented 

 in 1884. Since then a variety of "deformed" bars have been 

 placed on the market for concrete reinforcement. 



Among the best known and extensively used systems in Europe 

 is that of Frangois Hennebique, brought into use about 1892. 

 This deserves especial note as M. Hennebique was one of the 

 first to use beams of reinforced concrete and to study the theory 

 of their design. 



Most of the early formulae used in construction were purely 

 empirical, but since reinforced concrete has become a common 

 form of construction it is receiving much attention from engi- 

 neers ; experiments are being made on it and a vast amount of 

 information collected on the subject so that its design is no 

 longer a matter of guesswork. The design of a reinforced con- 

 crete structure is now a matter of just as exact calculations as 

 with any other structure material and its strength and perma- 

 nence are in no way in doubt. 



The question is sometimes asked as to the permanence of 

 reinforced concrete ; how do we know that a form of construc- 

 tion less than fifty years old will withstand the elements and the 

 depreciation of years without weakening and failure? For an- 

 swer we have only to refer to the permanence of the mortar and 

 concrete made by the Romans and other ancient builders. A 

 study of the use of mortar and concrete in their works leaves 

 no doubt as to the durability of the concrete itself. The test of 

 centuries is not needed to assure us of the behavior of the rein- 

 forcing steel, as the metal is thoroughly protected by the concrete 

 against corrosion, and the examination of iron that has been 

 embedded for years shows that no deterioration has taken place. 



The first use of reinforced concrete on a large scale in factory 

 construction was at the plant of the Pacific Coast Borax Co., 

 erected by Mr. Ransome in 1898. Afterwards the building passed 

 through a destructive fire and showed conclusively the ability 

 of such a structure to withstand the high temperature that would 

 have destroyed other structures. 



A study of the different systems of concrete reinforcement is 

 a most interesting one, but there are now so many that no at- 

 tempt will be made to go into details of any particular one. In 

 general it may be said that the metal is used in the form of bars, 



