CONCRETE.

Wairarapa Daily Times, Volume VIII, Issue 2245, 16 March 1886, Page 2

CONCRETE.

Rapid as has been the development of concrete during the last tew years, novor has'that progress been so mnrked than at the present time, whon scarcely an undertaking is carried out, be it cottage construction of the simplest type, or the public building vast in size- be the design insignificantly small, or the schome one involving, the outlay of millions, hut wo find constructors and contractors gladly availing themselves of this material, which unites so happily eaonomy and durability with ease in manipulation, and great adaptability to forms and shapes required. Concrete is no new thing, Tho Romans understood the employment of concrete; nor did tho builders of that day hesitate to press into their services the advantages derived from its use, with a skill and success to which at the present day the test of centuries bears ample testimony. To the great strides in all constructive art—to tho ever-pressing demand for cheaper materials—to the improvements which have been effected in the manufacture and manipulation of cement, as well aB the economy resulting from the introduction of special machinery for crushing stone—to those, amongst ofhef. considerations, mnst.we'lpol: causes which have resqlted ih tj}e' royival of concrete. Tho composition and preparation of concrete may'be chiefly explained, Concrete is an artificial agglomeration formed by an admixture of lime or cement with sand or gravel or broken rock. . The preparation of concrete, though exceedingly simple, requires to be carried out with system and regularity, if satisfactory results are to be obtained. The ingredients just mentioned have been well mixed by shovelling, water is added, and after further turning over the concrete is ready. All that remains to be done is to throw the viscid admixture into its final position—into the trench, where a foundation Is being formed-or between tho two parallel rows of planking, forming as it were a huge mould, and marking the position of a future concrete wall," fhe material rapidly astonishingly #rt period 'assumes' that monolithic hardness which is bo justly esteemed for solidity and stability, ' In countjy the cement usually employed in the preparation of concrete is that bearing the name qf Pprtland it 1b believed, tram its similarity in appearance to Portland stp.np. Portland cement is prepared by the' calcination 1 or burning of chalk and clay, and is manufactured in large quantities on the banks of the Thames and Medway, Tlio Band employed aids in the formation of a solid mass, by flUlne up Jntersticeshetween the larger material, It should be angular and sharp, also free froip extraneous matter. When it is impossible or undasirablo to use gravel, ornaltod stone, usually that of the neighbourhood, proviked it is suitable, is employed, When used in sufficiently large quantities to warrant tho employment of steam power, a stone-orushing machine is usually provided. The stone is broken to a size similar to that of road metal, Both as regards materials and composition, concrete necessarily presents considerable uariation. The< materials employed are those most available economically and physically; whilst the proportions of tho admixture depend on the qf work to be i\(i wel| on the individual judgme(i| of % ratio between (he quantity of foment and that of other material enip|oyed forms the standi by Vfhifiji concrete is known. Thus a six tq pqe concrete implies a material compounded of six parts by volume of gravel or orushed stone or brick, as the oase may be, with one part by volume of cement. An enumeration of the many purposes to which'concrete is ,now adapted would form a formidable list; suffice it te point out that in almost every class of construe tion, in the execution' of fysignb both' great and small, tlie economical advantages derived from its employment are more and more appreciated; -Chambers' Journal/ : '