THE BUILDING MATERIALS OF OTAGO.

Evening Star, Issue 4221, 6 September 1876, Page 4

THE BUILDING MATERIALS OF OTAGO.

The third paper on the above, treating of ei, cements, and aggregates, was read •vening at the-0tao;o Institute hy Mr . The following is an outline of it:— At the outset, Mi Blair explained that although &• terms lime and cement were used invariably to flwobs different and distinob articles, the cementntrttarMieats were the same In both cases, the auyroiffflrenoe-'being in the proportions in whioh ttMnrJoooar.: Pure lime is practically worthless for VvuVuitKj^nrposea; it never acquires the necessary ■rtp'fof strength in any situation, and never JKHra«n J st'ail rn a damp place. In order to make mast oontain a mixture of elay, the proportion varying from 8 .per cent, in «4inary building lime to 35 per cent, in strong hrtraulip oeinent. Limes and cements are equally tfjriaed into four olasses, according to their properlUin sad strength p—l..The oommon or rich limes that contain less 'sfiu£ W t>* cent, of clay or other impurities. _ ft. Poor limes, in whioh the impurities consist of fiseat 10 to 35 per cent, of sand or other isolnble in■Mdieatsvthat will not enter into chemical oomflbatiun with the lime, i. Hydranlie limes, such as contain from 10 io 80 gar.tmnt ofjalumi»i* and, soluble silica. •V HydratiHo eemente, containing from 80 to 40 yr oynt.,of, aluminia, soluble silica, and other lmThe adhesire'properties of the rich limes are

■hunger than their oohedre ones, conspquontlyi - 9**T sannot be used without a large admixture oft t*BMr,'.lt. is opntmon to hear the expression that. TMTMkr U injured by toe mnoh sand, but the obanoes "wtVWat its bad qualities are tbe result of the oppo-j sM» eondition, and above all thatth* sand and 1 m* «r« aot propsarly mixed..; If greater care was exeroi sed ta this behoof, so that an approach could be made; .. *• '•fw»«n eo>en atom of time, the resalt would ba a> 4e«bling of the stiength of rich lime'mortar. Poori takes possess all the bad qualities of the rich ones; M& have an additional draw backin irregularity of in ; •rasistenoy, through not slating so readilv, which feeoessitates grinding. Hydraulic limes are fre fuently subdivided into three or four section*; IMging from slightly to eminently hydraulic, th<» former being practically a rich lime, and tftie latter a cement. These limrs do not ■lake readily, nor do they expand much JB 3the ■ process. The higher kinds slnke so •lowly and so imperfectly that they are always pulr wised by grinding. Hydraulic limes set under water in from three to fourteen days, according to the Btrength of the sample—Hydraulic cementt •annotbe slaked by water in the usual way : tbej ariV properly speaking, not calcined but vitrified; the produee of the kilns resembles slag from a blast furnace, and it requires the aid of stone breakers, tron rollers, and Frenoh birr mill stoaes to convert ft into the cement of commerce. In common with the higher kinds of hydraulic Jime cement does not require any admixture of sand tomake it into morta< '.

' 'Rhas been ascertained by experiment, that the best pfoportisn of sand for rioali ies is fy to I,and for ptdm&ry hTdraulio hmee, 1 j to 1. ■ This explain* (v |Wj».,parti9JitT of bui ders to rich' limes, which, in ,|&<| own phraseology, "carry more sun l *," and «' mains.that strength and comfort are sacrificed for >° An'insignificant saving in ecst. There is no scarcity 'oHtm«Bnitable for building and agricultnral parLiyoMßrihxoutfioufc the Province. It ia known to .. : *ri»A.iaj.ponß)dßrab]o quantities in the Mlowinfr districts:—Oamaru, Otopopo, Waihemo, M»mototo ttalnv, Waikonaiti, Waimea, Winton, Aparima. "' l 'WaWu , ; f aSid Waikatipu. These localities are sp widely dispersed that we may s»fely calculate on a -ftrpply being-available for any demand that maj ■rise. .The only natural cement hitherto discovered {a Otago iB the well-known Septaria or cement boulders of the Moeraki district, which resemble in •very r respect the English atones from whicli Soman cement was originally maanfnctured. Aa- , fording to Dr Haast, the bonlders follow the c<>a3t from Snag Point to Terapnpn 0.-ek, then rnn in a straight line to the little Kuri Crerk, whieh is •traok at a point abont half a mile From the sea. In %&• first fonr miles the deposit iR a mere line of . boulders lying on the beaou or embeldod in the •'• cliSs, bnt on leaving the emit it expands into a "'•; .belt from twenty to thirty chains wide, and five nnd >i r ftnlf miles long. Many of the volcanic c'ays thai :!■ Axistin sneh profusion along the sea-hoard from BadSle Hill to Onraaru possess cemontitions pro- . . ftfflfties similar to the Pnizriolanas of Italy and the ''' Tyrass of the Ehino. The aggregates' proper consist 6f Bhingle, gravel, and sand, which have an almost -tmiversftl dlstribntion throushout tho--Province His apology for referring at lengtl- to tbeso foreira , materials, is that we hove hydraulic limes in Otago Mint are, so far as chemists can determine, identi °al with them in all their essential properties. In foot, ttfere is no difference in the composition of those* fcwo articles, the distrepancy in the analysis being In all cases within the limit of error claimed by the best analytical ohemi6ts. Proceeding to describe those to be found in Otago, he said that there was ...,a, yellowish-white conglomerate stone of a hard, ''compact nature, found three" and a-half miles from Oaraaru. This, he has- no hesitation in f renouncing the best ime for building purposes ;thertodiscovered in North Otago, and is very much ! etfperior to the lime in common use from the Kaka- : jxuia kflns. The limes from the Peninsula nnd ".. tower Harbor districts seem to be members of one •' torge deposit that extends from Seal Point on the ' 'tOTtbern side of the Peninsula to Dowling Bay on • tho northern shore of the Lower Harnor Tlie '■ brsWrh of this reef or dyke is uuknown.- probably it yi^Jf^noj^,more than' half-a-mile, and the aggregate ' fchiokness'of the seams now visible is at least 70ft There are five or six distinct; beds of varing quality and depth; as a rule they are well defined, particula ly near the upper nnd lower ::; rides* bat occasionally more, than one kind et i Stone is found in the same stratum. The . Feninsnla kilns (M'Donald's), the highest on the ' reef, only onrunts four beds; while the Glonmore (Bobeftson's) which a- e situated on a much lower level, show six tolerably distinct specimens from as many different layers. Two of them are, however b6 thin, that they can scarcely, be called beds, and it is also quite possible that they exist in a less marked degree in the upper quarry. There are five well - denned seams at Dowlbg Bay,' ■ four, of which have been analysed. Whether regarded as to structure, consistency" general appearance, or chemical composition, these Otago rookg exhibit aU the peculiarities of hydraulic limestones of no mean order. A practical test of them gave equally satisfactory results. A paroel • of English 1 blue liaa lime then in Dunedin, and the ordinary rich kind from Waihola, along with the j hydraulic sample from the Peninsula, were snb-

knitted to the same treatment and tested together, the results of whioh, taken in connection with the ehenrical teat, place this sample of Peninsula lime lo the olass of eminently hydraulic, as fixed by the beat' authorities. The Dowling Bay Beam should yield a very good hydraulic seam; for although it tnay be Bomewhat deficient in the ingredients that ensure hy iraulioity, it is absolutely free from those that; are supposed to have a contrary effect. A fawn-colored compact stone from the second highest Stratum at the Peninsula kilns bears a remarkable resemblance to the famouß Thiel limestone of France, aa was proved by an abstract of their respective ingredients. Specimens from the top seam at M'Donald's and the third at Dowliug Bay are Almost identical in composition and resemble closely the hydraulic limestones of Lyme Segis" of the Dorsetshire lias, while two samples—one from the third seam at Dowling Bay and the other from the lowest at the Peninsula quarl ries-flnd an English prototype in the blue lias of Holywell. Judging from the analyses the product of this bed might fairly be call- d cement stoues

They are in the highest cLsa of hydraulic limeatones, and seem to have all the attributes of a natural Portland cement, 'heir points of resemblance to the E glish materials was shown by a table; anl if the comparison were carried further it woulu t,e shown that there w still greater affinity between them and the English artides. There is less than a quarter per cent, difference between the quantities of magnesia in the Dowling Bay and Kolywell stones, and only a tenth per cent. .difference in oxide of 'ron between the latter aud the Peninsula one. The seam of this stone at Dow. ling Bay is 20f b thics, and there are also immense quantities on the Peninsula. The rock appears to be perfectly homogenous, so there is little danger it irregularity in burning whei once the proper temperature has been ascertained. If the qualities <rf this stone come up to his expectations—of whioh he has little fear—the value of the discovery to the community at large can scarcely be overrated; and from the researches that have been made, he ■is confident any failure that may take place will result from improper manipulation, and not from a defect in the raw material. Under the heading cf hydraulic cements Mr Blair discussed the value of Moeraki boulders for the manufacture of cement. The practi al results hitherto made with them have been irregnlar and Unsatisfactory. He thinks the irregularity in composition of the boulder is so preat that it would be practically imp -saibleto manufacture cement from them of a uniform quality, as one kiln might be equal to the best Po land and the next quite worthleas, wherefore he concludes the expeuse of selection on the one hand and the risk of failure on the ether nre 'ngnrmountable obsticles in the way of its general utilization. The re u t of his investigations with native Mments and limes were next d- tailed. When he

£OTua*noed them he wns under the impression that w» had no stones capable of furnishing hydr ulic lime*, but the discovery of natural oementii g iugredents of a high character having been fiiliy es-ta->l.«hod the necessity for adopting artificial substitute* was removed. Blue clays, supposed to be iruitable for oemcnt are abundant throughout the Province. An analysis of that in tho railway cu'. ting at Caverabam shown there is every ohanee of getting the proper kind if required. Portland eement is a low priced article, the value of j whioh is more than doubled by the charges of exportation, and it can be manufactured without much gkilied labor •, c"uaiqu"ntiy it is ai industry that mif b.t be started in New Zealand if there were no hydraulic limes to compete wirli it. The best puces in Otagolor a factory are the Waihouio i,nd ipariua distnots, both of which furnish soft limeitonosa d fuel—the main requisites. An examination of pur volcanic clays, to ascertain It they contained a>»y of the prut>erti<B of the PftZgrfanas of the O'd World, flat nave been used vtith lime in hydraulic -works, JeJd to forty 1 of alijsnatleß of color imafcin%ble being collected and tested Try being fjurie iotojttxtu with an eo.ua] proportion of lime

and then kept in water for two months. Four or five samples of drab aud neutral tints savo indications of being feebly hydrau ie, so possibly a completer intestitation would lead to the discovery of a material of c 'ngiderabh- utility. After deiailing a number of interesting experiments to determine tin relative merits of i n- Otigo sands as aggregates, Mr Blair thus recapitulated the lodine points of his paper, and considered its practical bearing. Leaving out t he materials in tables 2 and 4, which are comparatively valueless, the following will show the various purposes for which the Otago limes are suited, each class being capable of performing the functions of those under it as well as its own. ... .

Rich limes—9 to 14, white-washing-, and agricultural and caustic purposes only; 15 to 18.backwork in partitions and plastennjr; 10 to 23, low thin brink- walls in a dry situation. Hydraulic limes—ll to 13, ordinary walling above ground; 14 to 16, foundations of ordinary buildings, concrete and engineering structures above ground; 17 to 20, nearly all the higher class masonry for which cement is usually employed. The rich limes are nell dispens«d throughout the Province, but the hydraulieonesare confined to the preoints of Dunedin, except "Wakatipu deposits, tks hydraulicity of which has not been proved. Although lime has been burned at the Peninsula id many yearn, none of the good seams hav.o been utilised, because as tbe proprietors allege/there is SO market for tLfa quality. Builders will not use it in preference to the rich. lime,,aa the latter carried more sand, and -in the absendeof any information on the subject.professional men and the publio crsnerally have no choioe. Judging by the qm'ity of the ingredients of the mortars now used in Danedfn and the manner in which they are manipulated, he was not able to estimate the tensile strength of our ordinary lime mortars at mote than ten pounds per square inch, whioh i« less than,-, half the strength of Enropoan mortars that, are, demrnated bad. -Their, defects are quite apparent to anyo«e who takes the trouble to examine the aonthern side of a building. It wi3 be found that after a lapse of years the mOTfcr, even on the turfaee, is often quite soft and friahlft

A good example exists Jn the masonry of the Waitati bridge created in 1869. Although apparently well proportioned and prepared, the mortar in some places is still no harder than stiff olay. There is no greater auomally in the cons met ve arts than' what is displayed in the use of wenk mortar with strong brinks. "We might as well construct plate iron with lead r vets. In designing a bridge or a roof, every pnrt is RtiMincd alike, so that there is nothing wasted, hut in the 1 •aso before us three fourths of the work it thirty times stronger than the remainder. The oost of increasing the strength of our mortars is 3d and ton times 9d per cnbic yard of brichwork. These figures would only represent LlO and LSO on the new Tol graph Office, so the question of expense cannot stand in the way of the substitution of hydrunho limes for those in common use. At present the annual consumption of Portland coment in New: Zealand is ibout 40,000 casks, representing an expenditure to the consumer of L 40.000. Of this quantity, nine-'enths is used in works for which on J native products are equally well adapted} indeed, with the exception of some wet tunn 1 lining and foundations whoro qnicK set J tins wns a desideratum, there have b*en few works executed in New Zealand that reqnire oement. We are. therefore, spending LBB.OOO on a foreign article, while ft native one that, would serve our purpose can be obtained at half the cost. T*is state of affairs has resulted entirely from ignorance of our resources and of the quality of the materials within our roach. Tho principal hydraulic limestones of the Peniusnla are rather inscoessibl.y, situated. At present their only outlet is byToad to Dunedin. a distance of Un miles; but a moderate expenditure on a tramway two miles long would connect them with the proposed P<rt»hello Riilwav and the waters of the Har, bor. Tho deposit at Dowling Bay ocupies a very favornMe position on the beach, four miles below Port Chalmers. The new road to the Heads | asses through it, aod there is deep water within a few yards of the limestone rock. Im order to utilise these stores of hydraulic limes ta the best advantage, he snga-nsted the adoption of ri plan that seorai t» have been followed in America. The qmlity of the stone, not only in ©nch quarry, bnt in each, bed of that quarry, is so Hearl? determined, so that, its name conveys • distinct meaning to professional mon, who stipulate for certain kinds in certain work. Gradually tho names anqnire a commercial valno, like tho rands in ordinary manufactures, and thus the pnbuc generally scquire the knowledge necessary to ensure each article being used in its proper place. *

_ At the conclusion of the paper it was desired to propose a vote of thanks to Mr Blair, but it was pointed out that such a course was against the rules of t ,e Institute. All the speakers referred in eulogistic terms to Mr Blair's treatment of his subject;.