TABLE OF ANALYSIS OF VARIOUS NATURAL AND ARTIFICIAL CEMENTS.

An Eng. Portland. A good Portland. A Ger. Portland.

Manlius.

Ext'd. from Henry Reid's Treatise on Portla'd Cement. Dr. Manlius Smith of Syracuse, N.Y.

Napanee.

NOTE-The two samples of artificial cement shew that it is quite possible in short time tests to get a high result from an inferior article, as these samples deteriorate with age.

Mr. Hannaford.

DISCUSSION,

Mr. Hannaford said his experience with natural cements was not so favourable as with artificial cements, and that with the former the bulk was often inferior to the samples. In explanation of this, it may, and no doubt does, arise from the fact that the stone from which natural cement is manufactured is in beds, adjacent and mixed with ordinary limestone, and that the assorting of the one from the other, and the selection of the natural cement stone, even within its own compass, requires the most careful attention of experts, and that when a demand is made upon natural cement works for a large supply, it is reasonable to suppose that the selection of the stone is apt to be hurried; but be that as it may, his experience has been that as a rule natural cements do not hold their character throughout bulk, like artificial cement, and hence in carrying out works (especially under contract) this element affords much anxiety.

But assuming that the difficulty above mentioned may be overcome by care in selection and systematic manufacture, this process means additional cost; still, even so, can the output of natural cement meet the market demand, and is it equal to the artificial cements ?

He was unable to give a reply to the first query. There are several natural cement works in Canada, and all alike praise their output; but in regard to equality with artificial cements, his experience has been that none of them are to be relied upon in bulk for doing work equal to artificial cement. Artificial cement (Portland) has the qualities of quick setting, great cohesion, and resistance of sea water beyond all others, whilst it can be used freely with water to form "grout," which natural cements cannot be, and whilst water may be used freely with artificial cement, it must be used sparingly with natural cements.

In the way of concrete his experience has been that artificial cement was preferable to natural cement, and that he had failed to obtain results of hard setting in water from natural cement, whilst in sea water it refused to set. He had used natural cement in concrete but invariably laid in air.

Mr. W. E. Gower thought that Mr. Hannaford's claim as to the Mr. Gower. unreliability of the cement was fully borne out by the figures given by Mr. Butler, who gave 7 days' test at 90 lbs., one month's at 140, and 6 months' at 280. The figure given by Mr. Bravender showed a 7 days' test at 135 lbs. and a 27 days' test at 200 lbs. ; but on referring to a paper read before the Society by Mr. Rust, on the Construction of Sewers in Toronto,* he found the results of tests of Napanee cement showed for a 6 days' test 39 lbs. per sq. in. only, and a 30 days' test 76 lbs. only; these figures were considerably less than 50% of those given by either Mr. Bravender or Mr. Butler. He thought there was no doubt that Canadian cement could be made to stand a very high test, although he had not arrived at the figures given by the gentleman who said that he had tested the Hull cement and had attained the result of 676 per sq. inch for 7 days. He understood that the highest test cements known at present were German cements, and for a 7 days' test these did not attain the figures of the Hull test. In February, 1889, he tested four briquettes of artificial cement, and the result was from 325 to 219 lbs., one giving a very low test, the average being 292 lbs. for a 7 days' test.

Mr. Reid said it would not be prudent for him to say much about Mr. Reid. the quality of cement made in different parts of Canada. There could be no doubt that there was an abundance of suitable material here. The first Portland cement he made was in 1869 in Halifax, N. S. Material there was abundant and fuel cheap. A quantity of cement was then being sent out by the British Government for the harbour fortifications, and he made some native cement and subjected it to a test made by the Royal Engineers, then stationed there. At that time--21 years ago-Portland cement was scarcely known in Montreal, and comparatively little of it was used in New-York. He commended Mr. Thos. Arnold's method of testing samples:-Each of his small briquettes contained 135 grammes of cement compressed into a dry mould by screw pressure, which were then treated in water.

Mr. Dodwell considered that one of the most important features Mr. Dodwell. in the cement discussion was the desirability of a uniform system of testing. The want of such a system has been one of the great defects and difficulties in comparing tests of one cement with that of another, the systems of testing having been dissimilar, and anything

"Construction of Toronto Sewers," by C. H. Rust. Transactions, Vol. II, page 302, November, 1888.

H

Prof. McLeod.

Mr. Reid.

Prof. McLecd.

Mr. Reid.

Prof. McLec 1.

Mr. Dodwell.

Mr. Hopkins.

M. Reid.

Mr. Irwin.

that would tend towards uniformity in the testing of cement would be of very great advantage.

Professor McLeod asked if in the method mentioned by Mr. Reid the pressure was uniform?

Mr. Reid said the pressure was uniform, because the plunger was made precisely to fit the briquette, and when pressed down level it left exactly the space of one inch.

Professor McLeod understood the pressure was measured in that way by the volume which the powder occupied.

Mr. Reid said that a briquette mould would contain 135 grammes under certain pressure, and that this could not be overdone or overstrained so that there was uniformity in every briquette; a little tray filled with water was used in which the briquettes were placed.

Professor McLeod thought different cements would have different gravities, and it could not be expected that the same weight would always occupy the same volume.

Mr. Dodwell did not think the Arnold system was quite free from objections in some points, but the great point was that if it could be universally introduced as a standard of cement tests, that would be sufficient, as results would then be comparable, and the objections would be of no moment.

Mr. Hopkins considered that if there was a good deal of material containing iron ore it was better by not being tested in amounts of 135 grammes as the density would not be as great. That seemed to him to be the chief objection, because of the testing by the same unit of weight instead of volume.

Mr. Reid asked if that would not be apparent in the result of the briquette test?

Mr. Irwin said in any case cement was sold by the barrel, and its value determined by volume instead of by weight. He considered a good testing machine was much required.