FERRO-CONCRETE.

Gisborne Times, Volume XXVI, Issue 2097, 25 January 1908, Page 2 (Supplement)

FERRO-CONCRETE.

* A BUILDING REVOLUTIOJ N. (By A. T. Best, C.E., in London Daily Mail.”) Concr. te and stetfl are changing tho building world. The Romans first nesd concrete, the “signmum opus of Vitruvious, and many examples ot it still remain. The mortar ot Line and pebbles, with which medieaval builders bedded the masonry ot tlunr | castles and cathedrals, may be regarded as fine concrete. Old Newi °ato prison was built, ahuot 150 years 'ago, on a bed of lime concrete. ; Since the introduction. about JS-H) Ol I Portland cement. which forms a i stronger matrix than ordinal v 'mo, i cement concrete lias come into wide- ! spread use. for many purposes, from I gigantic dams down to common drain i pipes. i Iron also has been in use stuetnrnllv from very early .times, the olciest known example being, the pillar of Rajah Dhava at- Delhi, which bears a Sanskrit inscription ot the 'fourth century. In the Middle Ages, e however, the structural use ot iron \ ■' -j■•■

was generally restricted to suoli mior -forms as bingos, bolts, and other fastenings. In the eighteenth century iron began to enter largely into works of construction. Tho Coalhrookihvlo Bride, erected in 1777, was once of the first ill cast iron. The early nineteenth century saw wrought iron employed by Stoplioneou in the Alenni tubular bridge. Then came, in ISf.fi.the Bessemer procees, which revolutionised constructional engineering by facilitating the imimifncturo of steel on a largo scale and at a low cost. Tho Forth Bridge, erected twenty years ago, “the crowning triumph of tho age of steel.” absorbed in its construction alone some 50,000 tons.

THE ADVENT OF FERROCONCRETE.

But if concrete and steel are both fumi'liar by long-standing use, less familiar is* tho modern combination of the two materials, which is variously known ns armoured conereto, reinforced concrete, concrete-steel, or forro-conerete. Thou new method is of French origin. To Joseph Monior, a gardner, is attributed tho first idea of embedding in concrete an interlaced network, about the year 18G8, of iron rods or wires. And later developments are mainly due to“ French (or Swiss) inventors, among whom may be named llennebiquo, C’ottaiirin, and Considero. English, American, and other ognineers have also contributed to the advance, though in a lesser degree. In fact, tlio progress made in this matter affords a god example of the benefits derived,from international exchange* of ideas and tho rapidity with which nowadays an improvement originated in one country is known, investigated, adopted, ami further improved in another; for tho best, brains of all covilised nations are concentrated upon tho problem. Although of such comparatively recent introduction (for the principal patents were only taken out in the nineties), ferro-concroto has boon widely usod in both the Old and Now' Worlds. In conservative and citations England its adoption has' not as yet been so general as on the Cqntiunet and in America, yet even with us tho number of works already executed is very considearble. While tho Kahn system is perhaps the most extensively employed in the United States the Hcnnebique system .is prevalent in England as in France, and it is stateil that on the latter systen alone .something like 11,000 constructions have been carried out. At tho International Congress of Architects held last year, and by the profesional societies generally, much attention has been given to the matten in its technical aspects, and one periodical is entirely devoted to it. Regulations have been drawn up in Switzerland (1903) and in the United States (1906) respecting this form of construction —of which, as forecasted by one writer, “-the extensive use in al classes of building construction in tho near future is a certainty.” UNION IS STENGTH.

What then, is the principle of tho new method ? Briefly speaking, it is the employment of tho two materials in such a relation that tho tenacity of the one and tho solidity of the other are employed to the mutual advantage. To quote a French treatise: “Les ouvages en beton de ciment arme sont formes d’un squelette en pieces do fer ou d’acier noyees dans un beton de ciment . . . le * fer et le ciment se partagenk lo travail de resistence.” < That is t-o sav, a steel skeleton is encases in concrete and each takes its share of the stress. This happy combination may be compared to a marriage of two dissimiliar. but complementary natures, like our friend Jack Sprat and bis wife, of nursery rhyme celebrity. Concrete is strong to resist compression, but weak under tension; the.steel reinforcement is put in to “take up tho tensile stress,” being several hundred times as strong as concrete in this respect. At tho same time, tli concrete enveloping tho steel preserves it from misting, and from the effects of fire, stiffens it laterally, and generally gives solidity and" homogeneity to the structure. After severe tests by fire and explosives, ferro-concrte i sreputed to bo almost indestructible. Several buildings and bridges near San Francisco received the full force ot the earthqueko last year and suffered no damage. The destructive teredo, or sea-worm, has no terrors for it—nor can it rot as does timber, and the concrete increases in strength with age. RANGE OF APPLICATION.

This metliod of construction shows a remarkable adaptability to all purposes, from foundations piles to chimneys shafts. Piles of ferro-concrote can be driven into tho ground as well as, or better, than timber ones. For floors it lis, of course, eminently adapted . Bridges have been constructed in great numbers; a graceful bridg over tho Isar at Munich show- t ed its strength in the heavy floods of 1899, when the river flower right over it without damage, while an ad- f jacent masonry bridge was complete- J ly swept away. As another instance , of staba'lity under trying conditions, i a curious case wase reported in 1906 from Tunis. Owing to the failure of the ground, lofty ferro-concrete grain store tilted over to the extent of 25 degrees (the leaning tower of Pisa inclines at only*3*:or 4 degrees), and was subsequently.restored to vertically without distortion. . Building can Lfr erected with great rapidity entirely of this material, for factories, its freedom from vibraition adopts it for carrying running machinery. Wharves, warehouses, coal slid®, factory chimneys, aqueducts, and large .sewers are all made of ferro-eon Crete with advantage. Retaining walls on this principle require but a fraction of the mateiial formerly necessary. Large circular reservoirs (of which the walls need :he but a few inches thick) are much in vogue, especially on the Continent. The Bi'ooklanils motor racing track is formed of ferro-conorcto. '.Examples might bo multiplied but .enough hn s been said to indicate the Multifarious vises to winch this method of construction may he applied, vTo a certain extent, of course, there must bo considered the olnec■tion of the Irish orator, who cliallenvpd his audience to show him a building erected within recent years which h.ul successfully withstood the ravages of time for so long a. period as the monuments ot antiquity. Ihe searching test-of time lias yet to be endured. Moreover,, it is not to be expected that the newer method will oust older ones for all purposes, u 1 oi many works masonary remains tho most suitable material, for otheis timber, anil for others steel; but within its scone (a very wide one) it is a formidable rival, and must como into increasing use. The later nineteenth century was the age of steam and steel. But steam as a motive power is now largely superseded or supplemented by electricity; and steel in construction must inevitably mvo place, in a measure at least, to ferroconcrete. It will be Interesting to see whether the .adoption ot the newer methods in the early twentieth century will be sufficiently widespread" to give a name to the Age or Electricity anil of Ferro-Concrete.