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The Manufacture and Testing of Portland Cement.”’ by Major-General HENRYYOUNG DARRACOTT SCOTT, C.B., R.E., F.R.S., Assoc

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The Manufacture and Testing of Portland Cement.”’ by Major-General HENRYYOUNG DARRACOTT SCOTT, C.B., R.E., F.R.S., Assoc Proceedings.] SCOTT AND REDGRAVE ON PORTLAXDCEMENT. 67 11 May, 1880. WILLIAM HEKRY BARLOW, F.R.S., President, in the Chair. (Paper No. 1649.) “The Manufacture and Testing of Portland Cement.”’ By Major-General HENRYYOUNG DARRACOTT SCOTT, C.B., R.E., F.R.S., Assoc. Inst. C.E., and G1LBER.r RICHARDBEIIGKAVE, Assoc. Inst. C.E. NOTWITHSTANDINGthat much has been written concerning Portland cement, the history of its early manufacture is involved in con- siderableobscurity. Theinvestigations of Smeaton andPasley in England, of Fuchsand John in Germany, and of Vicat in France, into the nature and causes of the hydraulicity of limes, are well known ; but the discovery of the exact conditions of the manufacture of the cement now recognised as Portland seems to have been only gradually arrive& at. The first mention of acement named, in consequence of its fancied resemblance to Portland stone, “ Portland cement,” occurs inthe specification of a patent, KO. 5,022, grantedto Joseph Aspdin,a bricklayer of Leeds, dated October 21st, 1824. The cement originally made by Aspdin does not, however, appear tu have been a true Portland, nor was his process identical with that which has since been generally adopted in the production of this material. He used, in fact, a double system of calcination, as he employed a hard limestone in lieu of a soft and friable chalk. He specified, first burning t.he limestone to lime, so as to obtain a readily pulverised quicklime ; this lime he mixed with a suitable, or, as he terms it, “a specific quantity, of argillaceous earth or clay,” and then he directed that the mixture should be calcined “in a furnacesimilar to a limekiln, till the carbonic acid is entirely expelled.” This process of double calcination is perhaps, 1 The diacnssion upon this Paper wa8 taken together with that upon the two followiug ones. F2 Downloaded by [ University of Ottawa Library System] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. 68 SCOTT AND REDGRAVE ON PORTLAND CEMENT. [Minutes of in the absence of chalk, and where fuel is cheap, a readier way of preparing a cement than is that of grinding the limestone to a fine powder. Moreover, by this means the lime is obtained in the finest possible state of subdivision ; and its particles can thus be brought into a more favourablecondition for chemical action withthe minute particles of clay, than is thecase with thecarbonate of lime mechanically reduced to powder by grinding or crushing. It may he notedhere that Aspdin, the inventor, as he has been called, of Portland cement,, fails to indicate in hisspecification the requisite proportions of the two ingredients, and that his omission of the fact, that incipient vitrification must be reached in the process of calcination, would seem to throw serious doubts upon the authen- ticity of his discovery, at the date of his patent, of the material now known as Portland cement. There is reason to believe, however, t.hat he was certainly the first to insist upon the importance of partial vitrification, for his son, William Aspdin (who established a manufactory at Northfleet, on the Thames, where he traded, a few years after the date of his father’s discovery, as Maude, Jones, and Aspdin) was one of the earliest makers of true Portland. A little later young Aspdin is found in partnership with Robins, trading as Robins, Aspdin, and Co. ; and this firm, together with that of J. Bazley White and Co., may be considered tohave been the founders of thePortland cement manufacture in theLondon district.. It is singularthat Pasley,when writingt.he preface to thc second edition of his work on cement, in August 1847, states, on page xiii., “ At present there are threemanufactories of artificial cement in England, which have all been used more or less exten- sively in works of importance, and have given satisfaction.” He then enumerates them as follows :-First, that of Messrs. J. E. White and Sons, of Swanscombe, the successors to Mr. Frost (who attempted to make Portland), and who founded in 1825 the first factoryon theThames; secondly, that of Messrs. Evansand Nicholson, of Manchester ; thirdly, that of Mr. Richard Greaves, of Stratford-upon-Avon. Now all this time, asPasley himself ex- plained subsequently in a letter to Dr. Garthe, of Cologne, dated March 1852,’ Messrs. Robins, Aspdin, and Co. had been making Portland cement within 10 miles of where Pasley had been living at Chatham; and yet he had never heard of what they were doing, nor of the inventor’s manufactoryat Wakefield (established in 1825), until he accidentally met Dlr. Asprlin at the Exhibitionof 1851. ’ Vide “Dingler’s Polytechnischea Journal,” vol. cxxiv., p. 27. Downloaded by [ University of Ottawa Library System] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] SCOTT ANDREDGRAVE ON PORTLAND CEMENT. 69 In spite of the gradual growth of the new cement in public favour-due in all probability partly to the great estimation in which the cement patented by Messrs. Wyatt, Parker, and Co., in 1796, and known as (‘Roman cement,” was held ; and partly also to imperfections in its quality arisingfrom defective manufacture- Portland cement in time outlived all opposition, and as early as 1849 had come to be considered a better cement than Parker’s. As is too often the case with inventions of a practical nature in this country, scientific men paidvery little attention to thenew cement ; and even now the bulk of what is known respecting the chemistry of Portland cement is derived from German sources. The researches of Pettenkofer in its earlydays, and more recently those of Knapp, Schott, and Iiuhlmann, haveafforded a long series of patient and well-considered investigations concerning the action of cements, which may be sought for in vain among the annals of English laboratories. The first impulse to the more extended use of Portland cement may be traced back, undoubtedly,to the period when English engineers beganto institute careful andaccurate tests of the quality of the cementsupplied for works of importance. Thus it was not until Messrs. Rendel and I)ruce, and more especially &fr. Grant,had established the fact that Portland cement of a specified weight and density could be depended upon to undergo certain definite tests, that reliance bega,n to be placed in the new material, and thatconfidence in the meritsof Portland cement as a building material became fairly established. The admirable series of experiments upon the cement supplied for the Main Drainage Works of London, carried out for the Metropolitan Board of Works by Mr. John Grant, M. Inst. C.E., between the ycars 1869-1871, and communicated to the Institution of Civil Engineers in 18ti5 and 1871,’ constitute the basis of an accurate knowledge of the behaviour of Portland cement : and since Mr. Grant’s observations the records of Messrs. Colson,2Mann,3 and numerous otherobservers, have increased the store of information concerning the strength and characteristics of Portland cement. To Mr. Henry Reid, also, who has written a work4 upon this cement, the acknowledgments of the profession are due for the facts and statistics he has brought together. It is impossible to doubt that the adoption of certain - Vide Minutes of Proceedings Illat. C.E., vols. xxv., p. 66, and xxrii., IJ.266. * Ibid., vol. xli., p. 125. Ibid., vol. xlvii., p. 248. 4 ** The science and art of the manufacture of Portland cement.” Downloaded by [ University of Ottawa Library System] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. 70 SCOTT AND REDGRAVE ON PORTLAND CEMENT. minutes of rigidly imposed tests of quality has been of the utmost advantage in improving the manufacture, and in ensuring the uniform excel- lence of Portland cement. The Authors, afterhaving briefly considered thehistory of Portland cement, next examine the main features of its manu- facture,and at the same timetreat of thechemistry involved in the different processes. The plan of manufacture employed by the earlier makers in the Thames district has been followed, with but trifling modifications, by all manufacturers upto within a few years of the present, time. Recently, however, several important changes have been effected ; and the introduction of these processes by some of the leading firms has, so to speak, revolutionised the manufacture. In order toexplain these alterationsin the pre- paration of the cement, it will be necessary to referbriefly to the plan of manufacture formerly pursued. Concerning the materials, the Authors need say but little. Some have thought that the upper and lower chalk formations and the alluvial clayof the Medway afford the neplus ultraof the ingredients for Portland cement making. The fact is,however, that the proper mixture of carbonate of lime together with silica, alumina, iron, and the alkalies, such as shall ensure, when calcined and ground, a slow-setting,hydraulic cement of thePortland type, exists naturally compounded in numerous forms, and the clays and car- bonate of lime suitable for the purposes of the cement maker may be obtained innearly every part of the world. The danger in nsing a naturally compounded material, such, for instance, as the clayeylimestones of thelias formation,consists mainlyin the wide and frequent fluctuations which, almost without exception, characterise such beds, and expose themanufacturer to serious failures, unless more thanordinary care and watchfulness are exercised intheir selection. Examples of the extensiveuse of such natural cement compounds are furnished by the important manufactories at Roulogne-sur-Mer, inFrance, where the lower chalk is made use of, and by the employment of the lias beds at Rugby for the manufacture of Portland cement. It is useless to conceal the fact that the exact percentage of clay which is added to the lime is far less accurately determined than most manufacturers are willingto admit ; and, within certain not very clearly defined limits, all mixtures which contain say between 74 and 77 per cent.
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