NEW ZEALAND CEMENT.

New Zealand Times, Volume XXXVI, Issue 6272, 19 May 1881, Page 2

NEW ZEALAND CEMENT.

“ Portland ” is the name that, above all others, conveys the idea of excellence in the article of cement, and, accordingly, Portland cement has obtained a world-wide reputation, and follows closely in the track of the engineer and architect wherever they go, and that is almost everywhere. But if useful, and at the same time indispensable, Portland cement is also costly, and this fact has induced investigation in this colony with the view of providing a native production that shall at once and for ever obviate the necessity of any further importations from across the sea. That the raw material out of which Portland cement is manufactured existed in the colony had been ascertained beyond the possibility of cavil, and all that remained to be done was to devise means for its ready conversion into the cement of commerce. Onr readers would have observed a local in a late issue stating that two tenders for the production of one hundred tons of Portland cement each had been accepted by the Government, one of them being that of Mr. Decimua Atkinson. His price was £i 7s. 6d. per ton for cement delivered in casks, which is 12s. fid. leas than what is paid for the imported article. Keenly alive as we are to the necessity of developing local industry to the uttermost, we gladly accepted Mr. Atkinson’s invitation to examine specimens of his cement in various marketable forms, and also specimens illustrating the process of manufacture. We may premise our description by explaining where the raw material is found, and the conditions of its existence. Simply, then, immense and practically inexhaustible deposits of hydraulic limestone constitute a considerable portion of the geological formation north of Auckland. They extend from Mahu.rangi right across to Kaipara and to the north of Wangarei. In the latter place, the deposit is associated with coal, an essential condition of success in the production of the cement, fire being an indispensible factor. We were first shown the cement worked up into marketable form. There were three tiles, two of them each nine inches square by one inch thick, being made of pure cement ; the third—a paving tile—being made of three parts sand and one part cement. All three slabs were perfect in their way, the pure cement ones being hard, smooth, heavy, and of very close texture ; whilst the paving tile was more open and lighter, of rough surface, and admirably’ adapted for the purpose indicated by its name. It resisted indention by iron with wonderful tenacity, and was evidently stuff of any quantity of wear. The cement tiles almost turned the edge of steel. Moulds of cement, as they had been set in collar box covers and on glass, were then submitted to us and afforded occalar demonstration that in setting the cement neither expanded nor contracted ; whether the setting took place in water or in air, the cement invariably retained its normal bulk.

As Mr. Atkinson has obtained a patent for his process of manufacture, he has no objection to its being made public, and we therefore give it in accordance with his description. Firstly, the limestone is quarried and converted into lime by the usual slaking process. The powder lime is then mixed with water—sea water is the best for the purpose—and formed into blocks ready for roasting. The latter are then submitted to fervent heat, under which the white stone is converted into a dirty brown clinker. This is cement before grinding. The clinker is then ground into an impalpably fine powder, and so becomes the cement of commerce. Submitted to searching analysis the cement is proved to have almost exactly the same constituents as the cements of England and Germany. The products of Mr. Atkinson’s skill, research, and ingenuity have been closely examined by Mr. Blackett, Engineer-in-Chiet of the colony, and by Mr. Oliver, the Minister of Works. Both gentlemen are eminently practicual in this direction, and both accord unqualified commendation to the specimens. We were fortunate in procuring samples of the specimens, viz,, the limestone after conversion into the caked lime for roasting ; a piece of clinker ready for grinding; a ball or theoementaftermixingwith water and setting, the consistency being the same as that of the pure cement tiles; a piece of paving tile; and a portion of the cement in its pulverised form. These are to be seen at our office, and we cordially invite the inspection of all who are interested in such matters. We believe that a great discovery has been made that will be the means of establishing a mostimportant local industry in the colony, one that will not only provide for local wants but that will furnish the whole of Australasia with Portland (New Zealand) cement at prices defying competition from abroad. We were further informed by Mr. Atkinson that it was hia intention to proceed to Auckland in the course of a fortnight to carry out his contract. He has no doubt about the result, and abo that as soon as improved manufacturing appli-

nnces arc procured fno the old country, he will be able to supply cement in any quantity at about half the current rate 3. He is confident of this if the cement is delivered in bags, but if casks are vised it will be a little dearer. We are sure that this cement-manu-facturing undertaking will command the good wishes of every one bavin<r at heart the welfare and progress of the colony, and that the patronage of all who use cement will be exclusive! v accorded to the local manufacture.